electrical stimulation of the quadriceps muscle group in - School of ...

___________________________________________________Title pageELECTRICAL STIMULATION OF THE QUADRICEPSMUSCLE GROUP IN PATIENTS WITH PATELLOFEMORALPAIN SYNDROME.A thesis submitted to the University of Manchester for the degree of Doctor ofPhilosophy in the Faculty of Medicine, Dentistry, Nursing and Pharmacy.2001Michael James CallaghanCentre for Rehabilitation Science,1

___________________________________________________Table of ContentsTable of Contents1 INTRODUCTION .................................................................................................271.1 The problem ...............................................................................................281.2 The treatment.............................................................................................282 THE PATELLOFEMORAL JOINT.......................................................................332.1 Anatomy .....................................................................................................332.2 Biomechanics ............................................................................................342.2.1 Patellofemoral joint reaction force.................................................................352.2.2 Contact areas................................................................................................352.3 Patellofemoral Pain Syndrome.................................................................382.3.1 Nomenclature................................................................................................392.3.2 Aetiology .......................................................................................................392.3.2.1 Abnormal foot pronation ............................................................................402.3.2.2 Soft tissue tightness...................................................................................412.3.2.3 Proprioception dysfunction ........................................................................422.3.2.4 Muscle imbalance and weakness ..............................................................422.4 Quadriceps muscles..................................................................................432.4.1 Introduction ...................................................................................................432.4.2 Anatomy........................................................................................................442.4.3 Methods of Quadriceps exercise...................................................................473

___________________________________________________Table of Contents3 ELECTRICAL STIMULATION.............................................................................513.1 Introduction................................................................................................513.2 Electrical stimulation of animal muscle...................................................523.2.1 Calcium regulatory system changes .............................................................523.2.2 Myofibrillar apparatus changes .....................................................................533.2.3 Energy metabolism changes.........................................................................533.2.4 Neurogenic changes .....................................................................................543.2.5 Summary.......................................................................................................543.3 Electrical stimulation of human quadriceps muscle ..............................553.3.1 Quadriceps Strength .....................................................................................563.3.1.1 EMS or isometric exercise .........................................................................563.3.1.2 EMS or isokinetic exercise.........................................................................573.3.1.3 EMS and isometric or isokinetic exercise combined ..................................583.3.2 EMS at varying knee flexion angles ..............................................................593.3.2.1 Isometric strength gains.............................................................................593.3.2.2 Isokinetic strength gains ............................................................................603.3.3 Gender differences and strength improvement .............................................643.3.4 Quadriceps endurance..................................................................................643.4 Electrical stimulation of weak quadriceps muscle .................................663.4.1 Changes in isometric and isokinetic strength. ...............................................663.4.2 Electrical stimulation in PFPS .......................................................................703.5 Other muscle changes due to EMS..........................................................714

___________________________________________________Table of Contents3.5.1 Histology and Biochemistry...........................................................................713.5.2 Functional Measurements.............................................................................743.5.3 Thigh Girth ....................................................................................................763.6 Stimulation parameters.............................................................................773.6.1 Waveform......................................................................................................783.6.2 Pulse duration ...............................................................................................793.6.3 Duty Cycle.....................................................................................................793.6.4 Intensity and Length of stimulation................................................................803.6.4.1 Length of Treatment ..................................................................................833.6.5 Low Frequency versus High Frequency Stimulation .....................................853.6.6 Mixed Frequency Stimulation........................................................................893.7 Summary ....................................................................................................934 MEASUREMENT OF MUSCLE STRENGTH ......................................................964.1 Introduction................................................................................................964.2 Methods......................................................................................................994.2.1 Subjects ........................................................................................................994.2.2 Instrumentation ...........................................................................................1004.2.3 Procedure ...................................................................................................1014.2.4 Isokinetic testing..........................................................................................1024.2.5 Maximum Voluntary Isometric Contraction testing ......................................1024.3 Data Analysis ...........................................................................................1035

___________________________________________________Table of Contents4.4 Results......................................................................................................1044.5 Discussion ...............................................................................................1124.6 Conclusion ...............................................................................................1155 MEASUREMENT OF MUSCLE FATIGUE ........................................................1175.1 Introduction..............................................................................................1175.2 Methods....................................................................................................1225.2.1 Subjects ......................................................................................................1225.2.2 Force measurement ....................................................................................1235.2.3 EMG measurements ...................................................................................1245.2.4 EMG Data Collection...................................................................................1275.3 Data analysis............................................................................................1275.3.1 Statistics......................................................................................................1285.4 Results......................................................................................................1295.4.1 Torque measurements ................................................................................1305.4.2 EMG measurements ...................................................................................1305.4.2.1 Initial Median Frequency..........................................................................1305.4.2.2 Median Frequency ...................................................................................1305.5 Discussion ...............................................................................................1375.5.1.1 Initial median frequency...........................................................................1375.5.1.2 Median Frequency ...................................................................................1385.6 Conclusion ...............................................................................................1426

___________________________________________________Table of Contents6 MEASUREMENT OF PATELLAR PAIN ...........................................................1446.1 Visual Analogue Scale ............................................................................1446.2 Kujala Score.............................................................................................1457 MEASUREMENT OF QUADRICEPS CROSS SECTIONAL AREA..................1487.1 Introduction..............................................................................................1487.2 Method......................................................................................................1497.3 Statistical analysis...................................................................................1527.4 Results......................................................................................................1537.4.1 Intrarater reliability.......................................................................................1537.4.2 Location of muscle border...........................................................................1547.5 Conclusion ...............................................................................................1558 PILOT STUDY 8v8 ............................................................................................1578.1 Introduction..............................................................................................1578.2 Methods....................................................................................................1588.2.1 Subjects ......................................................................................................1588.2.1.1 Inclusion criteria.......................................................................................1588.2.1.2 Exclusion criteria......................................................................................1598.2.1.3 Clinical examination.................................................................................1598.3 Outcome measures .................................................................................1608.3.1 Instrumentation ...........................................................................................1607

___________________________________________________Table of Contents8.3.2 Isometric Strength.......................................................................................1608.3.3 Isokinetic strength .......................................................................................1618.3.4 Muscle Fatigue............................................................................................1628.3.5 Quadriceps Cross Sectional Area ...............................................................1638.3.6 Function ......................................................................................................1638.3.7 Pain.............................................................................................................1648.3.8 Clinical tests................................................................................................1648.3.8.1 Step up ....................................................................................................1648.3.8.2 Step down................................................................................................1648.3.8.3 Squat flexion............................................................................................1658.4 Treatment .................................................................................................1658.4.1 RESTIM ......................................................................................................1658.4.2 COMPEX ....................................................................................................1668.5 Statistical Analysis..................................................................................1678.6 Results......................................................................................................1688.6.1 Isometric Strength.......................................................................................1718.6.2 Isokinetic strength .......................................................................................1728.6.3 Muscle Fatigue............................................................................................1728.6.4 Quadriceps Cross Sectional Area ...............................................................1748.6.5 Function ......................................................................................................1758.6.6 Pain.............................................................................................................1758.6.7 Flexion ........................................................................................................1758

___________________________________________________Table of Contents8.6.8 Steps...........................................................................................................1768.7 Discussion ...............................................................................................1768.8 Limitations ...............................................................................................1788.9 Conclusions .............................................................................................1798.10 Considerations for the Main Study ........................................................1799 MAIN STUDY ....................................................................................................1839.1 Introduction..............................................................................................1839.2 Methodology ............................................................................................1839.2.1 The RESTIM stimulation regime .................................................................1839.2.2 The EMPI stimulation regime ......................................................................1869.2.3 Sample power calculations .........................................................................1899.2.4 Subjects ......................................................................................................1909.2.4.1 Inclusion Criteria ......................................................................................1909.2.4.2 Exclusion Criteria.....................................................................................1909.2.4.3 Clinical examination.................................................................................1909.2.5 Randomisation ............................................................................................1909.3 Outcome measures .................................................................................1919.3.1 Instrumentation ...........................................................................................1919.3.2 Isometric Strength.......................................................................................1929.3.3 Isokinetic torque..........................................................................................1939.3.4 Muscle Fatigue............................................................................................1939

___________________________________________________Table of Contents9.3.5 Quadriceps Cross Sectional Area ...............................................................1949.3.6 Function ......................................................................................................1949.3.7 Pain.............................................................................................................1959.3.8 Clinical tests................................................................................................1959.3.8.1 Step up ....................................................................................................1959.3.8.2 Step down................................................................................................1959.3.8.3 Knee Flexion............................................................................................1959.4 Statistical analysis...................................................................................1969.4.1 Normal Distribution of Data .........................................................................1969.4.2 Pre Treatment Analysis...............................................................................1969.4.3 Post Treatment Analysis .............................................................................1969.4.3.1 Multiple Regression Analysis...................................................................1979.4.3.2 Treatment Effect Size ..............................................................................2009.5 Results......................................................................................................2029.5.1 Patient Compliance .....................................................................................2029.5.2 Pooled groups versus Separate groups. .....................................................2049.5.3 Gender effects.............................................................................................2059.5.4 Correlations.................................................................................................2079.5.5 Isometric Strength.......................................................................................2119.5.5.1 Pre Treatment Analysis ...........................................................................2119.5.5.2 Post Treatment Analysis..........................................................................2119.5.5.3 Multiple Regression Analysis...................................................................21210

___________________________________________________Table of Contents9.5.6 Isokinetic Muscle strength...........................................................................2179.5.6.1 Pre Treatment Analysis ...........................................................................2179.5.6.2 Post Treatment Analysis..........................................................................2179.5.6.3 Multiple Regression Analysis...................................................................2189.5.7 Muscle Fatigue............................................................................................2219.5.7.1 VMO ........................................................................................................2219.5.7.2 VL ............................................................................................................2229.5.7.3 RF............................................................................................................2249.5.7.4 Quadriceps combined..............................................................................2259.5.7.5 Multiple Regression Analysis...................................................................2269.5.8 Pain.............................................................................................................2289.5.8.1 Pre Treatment Analysis ...........................................................................2289.5.8.2 Post Treatment Analysis..........................................................................2289.5.8.3 Multiple Regression Analysis...................................................................2309.5.9 Clinical Tests...............................................................................................2329.5.9.1 Pre Treatment Analysis - STEPS.............................................................2329.5.9.2 Post Treatment Analysis - STEPS ...........................................................2329.5.9.3 Multiple Regression Analysis - STEPS ....................................................2349.5.9.4 Pre Treatment Analysis - FLEXION .........................................................2369.5.9.5 Post Treatment Analysis - FLEXION .......................................................2369.5.9.6 Multiple Regression Analysis - FLEXION ................................................2379.5.10 Kujala Questionnaire...................................................................................24011

___________________________________________________Table of Contents9.5.10.1 Pre Treatment Analysis ...........................................................................2409.5.10.2 Post Treatment Analysis..........................................................................2409.5.10.3 Multiple Regression Analysis...................................................................2409.5.11 Quadriceps Cross Sectional Area ...............................................................2449.5.11.1 Pre Treatment Analysis ...........................................................................2449.5.11.2 Post Treatment Analysis..........................................................................2449.5.11.3 Multiple Regression Analysis...................................................................2449.5.11.4 Treatment Effect Size ..............................................................................2489.5.12 Gender effects.............................................................................................2499.6 Discussion ...............................................................................................2549.6.1 Baseline Data..............................................................................................2549.6.2 Treatment Compliance................................................................................2569.6.3 Changes in Muscle Strength .......................................................................2599.6.4 Changes in Muscle Fatigue.........................................................................2629.6.5 Changes in Pain..........................................................................................2659.6.6 Changes in Clinical Tests............................................................................2689.6.6.1 Steps .......................................................................................................2699.6.6.2 Flexion .....................................................................................................2709.6.7 Changes in Kujala questionnaire.................................................................2719.6.8 Changes in Quadriceps Cross Sectional Area ............................................2729.7 Limitations of and recommendations from the study ..........................2749.8 Conclusion ...............................................................................................27612

___________________________________________________Table of Contents9.9 Thesis Overview ......................................................................................2779.9.1 Inclusion and Exclusion Criteria ..................................................................2779.9.2 Sample Size................................................................................................2789.9.3 Autocorrelation............................................................................................2799.9.4 Compliance .................................................................................................2809.9.5 Reasons for No Differences between Groups.............................................28110 REFERENCES ..................................................................................................28311 APPENDICES ...................................................................................................31313

___________________________________________________Table of TablesTable of TablesTable 1. Comparison of strength/torque gains ..........................................................57Table 2. Percentage strength / torque gains ..............................................................62Table3. Comparison of Electrical Stimulation Parameters and delivery.....................63Table4. Frequency of EMS and effects on atrophied quadriceps muscle ..................84Table 5. Descriptive statistics for the subjects .........................................................105Table 6. Means±SD, 95% CI’s for all CKC measures. Healthy and PFPS groups...106Table 7 ICCs and SEM for Peak Torque. Healthy & PFPS groups..........................107Table8 Mean differences, 95% limits of agreements and 95% CI’s for QuadricepsStrength ............................................................................................................109Table 9 Group Means ±SD, ICC, and SEM for the IMF and MF ..............................132Table10 Means±SD & 95% CI’s for EMG MF slopes. Healthy and PFPS groups....133Table11 Mean differences, 95% limits of agreements and 95% CIs for QuadricepsEndurance ........................................................................................................134Table 12. A Two-way analysis of variance ANOVA for the MF slope.......................139Table 13 Intrarater reliability of ultrasound scanning technique ...............................154Table14 Muscle strength, pain and functional data. Means ±SD of mean changes. 170Table 15 Results of Repeated Measures ANOVA ...................................................171Table 16 Repeated Measures ANOVA for quadriceps muscle fatigue data.............174Table 17 Quadriceps muscle fatigue data................................................................174Table 18 Sample Size Calculations .........................................................................189Table 19 Descriptive statistics of patients completed (Means ± SD)........................20414

___________________________________________________Table of TablesTable 20 The distribution of the affected side and leg dominance (Means ± SD) ....204Table 21 Correlation Matrix of Pre Treatment Variables ..........................................208Table 22 Correlation Matrix of Treatment Compliance and Outcome Change.........209Table 23. Correlation matrix for Post Treatment Variables ......................................210Table 24 Association of each continuous baseline covariate and compliance.........213Table 25 Association of dichotomous baseline covariate.........................................213Table 26 Multiple Regression Analysis, Model summary.........................................216Table 27 Association of each continuous baseline covariates and compliance .......219Table 28 Association of dichotomous baseline covariates.......................................219Table 29 Multiple Regression Analysis Model Summary .........................................220Table 30. Association of each continuous baseline covariate and compliance........226Table 31. Association of dichotomous baseline covariates......................................227Table 32 Multiple Regression Analysis Model Summary .........................................227Table 33 Association of each continuous baseline covariate and compliance.........230Table 34 Association of dichotomous baseline covariates.......................................231Table 35 Multiple Regression Analysis Model Summary .........................................231Table 36. Association of each continuous baseline covariate and compliance........234Table 37. Association of dichotomous baseline covariates......................................235Table 38. Multiple Regression Analysis Model Summary ........................................236Table 39 Association of each continuous baseline covariate and compliance.........238Table 40 Association of dichotomous baseline covariates.......................................238Table 41 Multiple Regression Model Summary........................................................23915

___________________________________________________Table of TablesTable 42 Association of each continuous baseline covariate and compliance.........242Table 43 Association of dichotomous baseline covariates.......................................242Table 44 Multiple Regression Analysis Model Summary .........................................243Table 45 Association of each continuous baseline covariate and compliance.........246Table 46 Association of dichotomous baseline covariates.......................................246Table 47 Multiple Regression Analysis Model Summary .........................................247Table 48 Means ± SD or Medians (IQR), pre and post stimulation data. .................251Table 49. Quadriceps fatigue data. Means ±SD for normalised slopes ...................251Table 50. Between group analysis. Independent ‘t’ tests for normalised data .........252Table 51. Between group analysis. Mann Whitney U tests for non-normalised data253Table 52. Power sample calculation from the Main study ........................................25316

___________________________________________________Table of FiguresTable of FiguresFigure 1 Gross anatomy of the articular surface of the patella...................................37Figure 2 Diagram of the Patellofemoral Joint Reaction Force (PFJRF) .....................37Figure 3 Diagram of contact areas from full knee extension to full flexion .................38Figure 4 Cross section of the quadriceps femoris muscle group................................46Figure 5 Direction of pull of the Quadriceps...............................................................47Figure 6. Anterior view of the superficial quadriceps femoris. ......................................48Figure 7 Patient position using the CKC device on the Biodex dynamometer. ........101Figure 8. Bland & Altman plot, MVIC trials 2 & 3, healthy subjects. Means ± 2SD ..110Figure 9. Bland & Altman plot for CKC extension trials 2 & 3. Means ± 2SD...........110Figure 10. Bland & Altman plot for CKC flexion trials 2 & 3. Means ± 2SD..............110Figure 11. Bland & Altman plot, MVIC trials 2 & 3, PFPS patients. Means ± 2SD ...111Figure 12. Bland & Altman plot for CKC extension trials 2 & 3. Means ± 2SD.........111Figure 13. Bland & Altman plot for CKC flexion trials 2 & 3. Means ± 2SD..............111Figure 14 Graph showing compression of power spectrum .....................................119Figure 15 Representation of intercept and linear regression slope..........................120Figure 16. Use of acetate(left) allowed accurate repositioning of skin marks(right) .125Figure 17. EMG electrodes connected to the Biopac Tel 100..................................126Figure 18 A typical normalised graph of data from Vastus Lateralis (VL) ................128Figure 19.Bland & Altman Plot, trials 2 & 3 for VMO,healthy subjects.Means ±2SD 135Figure 20. Bland & Altman Plot, trials 2 & 3 for VL, healthy subjects. Means ± 2SD135Figure 21. Bland & Altman Plot, trials 2 & 3 for RF, healthy subjects. Means ± 2SD13517

___________________________________________________Table of FiguresFigure 22. Bland & Altman Plot, trials 2 & 3 for VMO, PFPS patients. Means ±2SD136Figure 23. Bland & Altman Plot, trials 2 & 3 for VL, PFPS patients. Means ± 2SD ..136Figure 24. Bland & Altman Plot, trials 2 & 3 for RF, PFPS patients. Means ± 2SD..136Figure 25. Compound B ultrasound scanning..........................................................150Figure 26 Image produced by Compound B scanner...............................................151Figure 27. A detailed cross section of quadriceps for comparison...........................151Figure 28. Bland & Altman plot for CSA measures between days. Means ± 2SD....155Figure 29 Flow diagram of the Pilot study protocol ..................................................170Figure 30. Mean ± SD Plots of median frequency slope differences(%/s) ...............173Figure 31. Stimulation pattern for the RESTIM device. ............................................184Figure 32 Electrode placement (in white) for the RESTIM stimulator.......................185Figure 33. Stimulation pattern for the EMPI device..................................................186Figure 34 Electrode placement (in white) for the EMPI stimulator ...........................187Figure 35 The RESTIM device and electrodes ........................................................188Figure 36 The EMPI device and electrodes .............................................................188Figure 37 Flow diagram of the protocol of the Main study. ......................................201Figure 38 Distribution of compliance data for RESTIM and EMPI............................203Figure 39 Gender differences in the RESTIM group for all outcome measures.......206Figure 40 Gender differences in the EMPI group for all outcome measures............206Figure 41 Mean ± SD of pre and post test differences for isometric peak torque.....212Figure 42 Histogram of normal distribution for isometric strength...........................215Figure 43 Scatterplot of residuals for isometric strength ..........................................21518

___________________________________________________Table of FiguresFigure 44. Mean ± SD of pre and post test differences for isokinetic peak torque ...218Figure 45 Mean ±SD of the pre and post test differences for VMO fatigue slopes...222Figure 46. Mean ±SD of pre and post differences for VL fatigue slopes ..................223Figure 47. Mean ±SD for RF fatigue slope pre and post test differences.................224Figure 48. Mean ±SD for combined quadriceps slopes ...........................................225Figure 49. Median and IQR for pre and post test pain differences...........................229Figure 50. Medians and IQR for pre and post test steps differences .......................233Figure 51. Mean ± SD for pre and post test flexion differences ...............................237Figure 52. Mean ± SD for Kujala score pre and post test differences ......................241Figure 53. Mean ± SD for quadriceps CSA pre and post test differences................24519

___________________________________________________AbstractAbstractBACKGROUND. Patellofemoral pain syndrome (PFPS) is often treatedconservatively with voluntary exercise for the quadriceps femoris. Nevertheless, asubstantial percentage of patients remain symptomatic. Although exercise seems acrucial element for treatment, it may serve to increase patellar irritation with theresulting dilemma that patients exercising the muscles may be simultaneouslyirritating the knee. One resolution to this problem may lie in exercising the musclewith electromuscular stimulation. PFPS patients have previously used uniformpatterned frequency stimulation, with varying results on muscle strength, atrophy andpain. However, there are problems associated with these forms of stimulation in thatthey address only the strength or endurance components of a muscle. This thesissought to explore the effects from a new form of stimulation in the context of PFPS.AIM. To compare a commercially available electrical muscle stimulation regime with anew form of stimulation for the rehabilitation of the quadriceps in patients with PFPS.The null hypothesis was that there would be no difference in outcome between thetwo types of stimulation.METHODS. A double blinded randomised trial was conducted with a parallel groupcontrol. 80 patients (33 male, 47 female) with patellofemoral pain were randomlyallocated to one of two treatment groups. One group received a uniform constantfrequency stimulation pattern of 35Hz (EMPI). The other group received a newexperimental form of stimulation that contains simultaneous mixed frequencycomponents (RESTIM). Subjective and objective outcome measures were isometricand isokinetic extension strength, muscle fatigue, pain, a functional questionnaire, astep test, knee flexion and quadriceps cross sectional area. Where necessary, validityand reliability studies were undertaken to ensure complete rigor of assessment.Treatment lasted for 6 weeks for one hour per day, a total of 42 treatments.RESULTS. 74 patients (31 male, 43 female) completed the trial. Although there weresignificant within group improvements in all outcome measures for both groups (p 0.05) in any outcomeexcept quadriceps cross sectional area.CONCLUSION. This study has provided data on a heterogeneous sample of PFPSpatients that is representative of the typical groups of patients seen in NHSorthopaedic and physiotherapy departments. As such the results are reasonablygeneralisable to the population with PFPS. It has shown that one form of stimulationwas just as efficacious as the other in improving subjective and objective measures.Due to the lack of statistical significance between the groups the null hypothesis wasaccepted.20

___________________________________________________DeclarationsDeclaration of Authorship and CopyrightDeclarationNo portion of the work referred to in the thesis has been submitted in support of anapplication for another degree or qualification of this any other university or otherinstitute of learning.CopyrightCopyright in text of this thesis rests with the author. Copies (by any process) either infull, or of extracts, may be made only in accordance with instructions given by theauthor or lodged in the John Rylands University Library. This page must form any partof such copies made. Further copies (by any process) of copies in accordance withsuch instructions may not be made without the permission (in writing) of the author.The ownership of any intellectual property right, which may be described in this thesisis vested in the University of Manchester, subject to any prior agreement to thecontrary, and may not be made available for use by third parties without writtenpermission of the University, which will prescribe the terms and conditions of anysuch agreement.Further information on the conditions under which disclosure and exploitation maytake place is available from Professor K. Luker, Head of the School of Nursing,Midwifery and Health Visiting22

__________________________________________________List of AbbreviationsList of abbreviationsACL = anterior cruciate ligamentAKP = anterior knee painANOVA = analysis of varianceBMI = body mass indexCI = confidence intervalsCKC = closed kinetic chainCMP = chondromalacia patellaeCSA = cross sectional areaCT = computerised axial tomographyCV = coefficient of variationcm = centimetrescm 2 = centimetres squaredEMG = electromyographyEMS = electromuscular stimulationHz = HertzICC = intraclass correlation coefficientsIMF = initial median frequencyIPI = interpulse intervalIQR = interquartile rangesmA = milliampsmin = minutesms = millisecondsmm = millimetresMF = median frequencyMJ = multi jointMR magnetic resonance imagingMVIC = maximum voluntary isometriccontractionMVIT = maximum voluntary isometrictorquen = number of subjects / patients in astudyNm = Newton metresOKC = open kinetic chainPNMS = patterned neuromuscularstimulationPFJFR = patellofemoral joint reactionforcePFPS = patellofemoral pain syndromeRCT = randomised controlled trialRF = rectus femorisSD = standard deviationSDD = smallest detectable differenceSEM = standard error of measureSJ = single jointTENS = transcutaneous electricalnerve stimulationVAS = visual analogue scaleVMO = vastus medialis obliqueVML = vastus medialis longusVL = vastus lateralisVI = vastus intermediusµs = microseconds± = plus or minus0/ s = degrees per second,kΩ kilo ohms,23

__________________________________________________List of PublicationsPublications Arising from this workCallaghan MJ, Oldham JA, Winstanley J. A comparison of two types of electricalstimulation of the quadriceps in the treatment of patellofemoral pain syndrome. A Pilotstudy. Clinical Rehabilitation. 2001; 15(6): 636-646Callaghan MJ, Al-Zharani E, McCarthy CJ, Oldham JA, Doherty P. Reliability ofsurface EMG measures during closed kinetic chain testing.Physiotherapy 2001; 87(2):88Callaghan MJ, McCarthy CJ, Oldham JA. Electromyographic fatigue characteristicsof the quadriceps in patellofemoral pain syndrome. Manual Therapy. 2001 6(1):27-33Callaghan MJ, McCarthy, CJ, Al-Omar A. Comparing open and closed kinetic chainisokinetic assessments. Isokinetics and Exercise Science. 2001(in press):Callaghan MJ, McCarthy CJ, Al-Omar A, Oldham JA. The reliability of multi jointisokinetic and isometric assessments in a healthy and patient populationClinical Biomechanics. 2000; 15: 678-683Callaghan MJ, Oldham JA. A critical review of electrical stimulation of the quadricepsmuscles. Critical Reviews in Physical Rehabilitation Medicine 1997; 9: 301-314.Callaghan MJ, Oldham JA. The role of quadriceps exercise in the treatment ofpatellofemoral pain. Sports Medicine. 1996; 21: 384-391.24

__________________________________________________DedicationDEDICATIONThis thesis is dedicated with love and thanks to my late Father,my Mother, my brothers and sisters and their families and children.25

__________________________________________________Chapter 1Chapter 1INTRODUCTION26

__________________________________________________Chapter 11 INTRODUCTIONPatellofemoral pain has been variously described as the ‘black hole of orthopaedics’ 1an enigma 1 , and a ‘mosaic of pathology’ 2 . A less flamboyant and dramatic description -'Patellofemoral Pain Syndrome (PFPS)'- is now commonly used in preference to theambivalent term ‘chondromalacia patellae’, although the terminology and nomenclatureare constantly changing. PFPS refers to the clinical presentation of anterior knee painrelated to changes in the patellofemoral joint 3 . PFPS is a common condition andpresents a difficult problem for surgeons, therapists and patients alike. Patients presentmainly with peripatellar pain of insidious onset. This can brought on by prolonged sitting(the so called 'theatre goer's sign'); by ascending and descending stairs, squatting,kneeling and by athletic activity. Clinical assessment of patients reveals a generalpaucity of abnormal physical findings. PFPS is considered to have an uncertainaetiology with numerous theories propounded including tightness of soft tissue andperiarticular structures, patellofemoral malalignment and maltracking, tibial torsion andgait abnormalities. These commonly cited theories for PFPS have been supplementedrecently by nerve damage in the lateral retinaculum 4;5 and patellar bone hypertension 6 .Another proposal is that PFPS may develop due to a dysfunction of the extensormechanism. This dysfunction has been variously described as generalised quadricepsweakness and wasting 7;8 , decreased eccentric function 9 , or differences in the activationpatterns of the vastus medialis oblique (VMO) and vastus lateralis(VL) 10 . To date it is stillunknown if the quadriceps dysfunction causes the patellar pain, or the pain causes thedysfunction 11 .27

__________________________________________________Chapter 11.1 The problemSeveral long term follow up studies have indicated that overall outcome with nonoperative treatment of PFPS is generally good, with most patients rarely using analgesiaand reporting subjective and displaying functional recovery 12;13 . Nevertheless, one studyfound that 33% of patients still had symptoms or objective signs at seven years 13 ,whereas another revealed 25% still having significant symptoms at 20 years 12 . This isnot an unsubstantial group of patients, yet these studies indicate that conservativetreatment is the mainstay for this condition. There is no consensus regarding whatconstitutes an appropriate conservative approach to treatment for PFPS. Attempts havebeen made to correct extensor dysfunctions by differing methods of exercising thequadriceps. Unfortunately exercise, which seems to be a crucial component ofconservative treatment 14;15 , often serves to increase patellar irritation with a subsequentworsening of patellofemoral pain 16 . This study attempts to address this conundrum.Namely, how can the quadriceps be stimulated and exercised without concomitantirritation of the patellofemoral joint? The answer may lie in electrical stimulation of thequadriceps.1.2 The treatmentElectromyostimulation (EMS) represents an artificial means of activating muscle thatbypasses the processes associated with a voluntary contraction 17 . Ever sincemethods of generating and storing electricity were first discovered in the 1740’s there28

__________________________________________________Chapter 1has been considerable interest in the role that electrical activity plays in treatingillness 18 . Such interest has escalated since the work of Galvani who demonstratedthat a muscular contraction could be elicited by an externally applied current 19 .Galvanism was superseded by Faradism in the 1830’s, which continued to be themainstay of treatment by stimulation to human skeletal muscle until the 1960’s. At thistime, Salmons and Vrbova 20were amongst those experimenting on animals withchronic low frequency stimulation (i.e. 10Hz, 24 hours daily for several weeks).Discovering the ability of EMS to change muscle fibre type helped them to formulatethe theory of ‘muscle plasticity’. In the late 1970’s and early 1980’s Farragher andKidd used uniform low frequency stimulation (9 Hz) to treat the predominantly type 1facial muscles in patients with Bell’s Palsy and coined the term ‘eutrophic stimulation’meaning supplying nutrients to the muscle (i.e. τροφή (trophic) = nutrition). The firstprotocol to use non-uniformed frequencies to human muscles was established in thelate 1980’s by Oldham and Kidd 21 . This involved extracting the firing pattern from atype 1 motor unit from the first dorsal interosseus muscles of the hand resulting in theintroduction of patterned neuromuscular stimulation (PNMS). This was very effectivefor the hand but extrapolation to other muscles proved problematic. At the same timein the United Kingdom, Laycock 22 was experimenting with EMS for the female pelvicfloor musculature using Interferential Therapy. With this, a uniform pulse train wasgenerated by two currents (2000Hz and 2050Hz) that ‘interfered’ with each other(hence ‘interfer-ential’) with the resultant frequency of 50Hz being delivered to themuscle. This was later changed to 35Hz after consultation with physiologists in the29

__________________________________________________Chapter 1United Kingdom and parts of eastern Europe (Laycock, personal communication).Although this new approach was designed to ease patient discomfort duringstimulation, the frequencies used were still uniform. By the mid 1990’s attention hadturned to developing a non-uniform frequency train based on an ‘iterative pattern’ byJarvis and others in animals 23 and by Armstrong in the human hand 24 . This was socalled because in order to obtain the non-uniform pattern, impulses at variousinterpulse intervals (IPI’s) were delivered to the muscle and once the maximum forceor force-time integral was established, the various IPI’s were ‘re-iterated’ to obtain themaximum or force-time integral for the second IPI and so on. In the human hand, theeffectiveness this iterative pattern was limited when compared to uniform frequencyEMS. At the beginning of the 21 st century, the three concepts of PNMS, the iterativepattern and the use of ‘doublets’ (double impulses with a short IPI at the beginning ofthe pulse train 25 ) have been brought together to form a further novel development forEMS – that of simultaneous non-uniform mixed frequency simulation with high,medium and low frequency components. For the later experiments in Chapter 8 andChapter 9, this new form of EMS was termed RESTIM.EMS has been used for quadriceps rehabilitation in many knee conditions includingPFPS either as part of a rehabilitation prescription 26;27 28;29 or occasionally part of aresearch trial 30 . EMS has several advantages over a standard quadriceps regime.Firstly, treatment can be standardised thus reducing error in performing the exercise.Secondly, thanks to in built electronic data collection, progress and compliance can bemonitored. Thirdly, the new generation of electrical stimulator permits this treatment30

__________________________________________________Chapter 1regime to be performed in the patient’s home, thus reducing costs to outpatientphysiotherapy and the patient. Furthermore, the pattern of stimulation delivered to themuscle can be precisely controlled independently of the patient or subject 31 .In order for a muscle such as the quadriceps to operate to optimum efficiency itrequires both strength and endurance characteristics. Existing EMS is designed toproduce a continuous pulse train of either low or high frequency stimulation. This isproblematic as low frequency stimulation (characteristically between 1Hz – 10Hz) isused to increase fatigue characteristics of a muscle, but at the expense of powergeneration 23 . On other hand, if stimulation is used to increase power this is at theexpense of fatigue 32 . Many existing EMS devices have higher frequencies between30 – 50Hz, giving little choice to the clinician and patient. A combination of these twoelements in a sequential stimulation regime whereby periods of low-frequencystimulation are accompanied by high-frequency periods may be advantageous. Thisis a physiological approach to stimulation as motor nerve firing patterns usuallyaddress both factors simultaneously.The object of this study was to evaluate a new form of EMS that incorporated asimultaneous mixed frequency pulse train to affect both strength and fatiguecharacteristics of the quadriceps muscles. The patient group was that of PFPS.31

__________________________________________________Chapter 2Chapter 2THEPATELLOFEMORAL JOINT32

__________________________________________________Chapter 22 THE PATELLOFEMORAL JOINT2.1 AnatomyThe presence of a bony patella appears to be important in terrestrial existence 33 , andthe distinctive characteristics of the design of the knee were established more than300 million years ago 34 .The patella is the largest sesamoid bone in the body with an undersurface possessing,at a depth of 4-5 mm at the central portion - the thickest articular cartilage of all joints 33 .This cartilage is avascular and aneural and its function is to spread the force of contactover a large area, thus preventing stress concentrations of bone to bone contact. Themechanical action of patellofemoral compression helps to provide nutrition to thecartilage.The articular surface of the patella has a smaller medial and a larger lateral convexfacet, which are separated by a vertical ridge. At the extreme of the medial border thereexists a smaller facet, described as the 'odd facet' 35 which is separated by a 2nd verticalridge (Figure 1). This ridge corresponds to the femoral groove (also called the trochlearnotch) that can vary in its shape and configuration between broad and shallow or a more‘V’ shaped groove. This variation in the boney structure of the patella and femuraccounts for differences in stability between individuals.33

__________________________________________________Chapter 22.2 BiomechanicsThe primary role of the patella is to enhance the extensor moment arm of thequadriceps 1 and increase its efficiency and mechanical advantage 36;37 . It also has a rolein distributing the compressive forces on the femur by increasing the contact area on thefemur. It has a minor role in protecting the anterior surface of the knee 1and inimproving the aesthetic appearance of the anterior aspect of the knee 37 .The patella provides a fulcrum for the static and dynamic stabilisation supports 29;36;38 .The static stabilisers of the patella are the joint capsule; the medial and lateral patellarretinaculum; the medial and lateral patellofemoral ligaments; the iliotibial band; theprepatella, infrapatella, pes anserinus bursae and several minor bursae; and the anteriorfat pad.Dynamically, the main supports are the quadriceps muscle group. The vastus medialisoblique has been described separately as the medial dynamic stabiliser 38;39 . Otherdynamic stabilisers are the posterior thigh group of biceps femoris, semitendinosus,semimembranosus and gracilis that control internal and external rotation of the kneeand knee flexion; this can affect patellar tracking significantly. It is also thought that tighthamstrings can lead to patellofemoral symptoms due to their insertion into the patellarretinaculum laterally 38 .34

__________________________________________________Chapter 22.2.1 Patellofemoral joint reaction force.The patellofemoral joint reaction force (PFJRF) is the compressive force acting on thepatella (Figure 2). It has been described formally as the force which most equilibratesthe patella and its equal and opposite, to the resultant of the patellar tendon andquadriceps force 40 . Many studies have described the PFJRF during a variety ofactivities 29;37;38;41 . There is a general consensus that an increase of activity from levelwalking to running will increase the PFJRF. This is due to an increase in knee flexionand quadriceps and patella tendon tension. This also occurs with other activities such assquatting, or descending stairs. Other authors suggest that tight hamstrings will increasethe patellofemoral joint reaction force during the gait stance phase 42 or antagonise thequadriceps function and cause greater patellofemoral joint loading 43The force of the quadriceps has to increase as the knee extends due to the loss ofmechanical advantage and so exerts most force during the last 15 0 of extension 29 . Themost effective line of pull for the quadriceps is parallel to the femoral shaft, passing 10 0lateral from a perpendicular through the axis of motion. This predisposes the abnormalknee joint to lateral patella drift, an effect that is increased with the more widely placedhips of the female 44 .2.2.2 Contact areasPFJRF becomes more relevant clinically when it is related to patellofemoral contactareas 33 that are points of contact on the articular surfaces of the patella and femur35

__________________________________________________Chapter 2(Figure 3). The patellofemoral contact area increases with knee flexion as does thePFJRF. This helps maintain some constant load distribution 33 .Investigations by Goodfellow et al. 35 found that as the knee joint moved from extensionto flexion a band of contact moved upwards (proximally) over the patella surface. Asknee flexion increased the band moved further upwards and became broader. At 90 0flexion the contact area on the patella reached its upper pole. Goodfellow et al. 35 noticedthat there was an area on the medial margin of the patella which did not make contactwith the patella from 0 0 -90 0 of flexion. This was called the 'odd medial facet' that wasseparated from the proper medial facet by a ridge. Further knee flexion to 135 0 showedthat the contact areas divided into medial and lateral zones with the medial zone exactlyfitting the 'odd facet'.Other authors have since described these contact areas 37 . Some authors have takeninto account the position of the quadriceps tendon and the presence of pathology at thepatellofemoral joint 29;39 .36

__________________________________________________Chapter 2Figure 1 Gross anatomy of the articular surface of the patella(From Clin.Orthop.Rel.Res. 1979 144, reproduced with permission)Figure 2 Diagram of the Patellofemoral Joint Reaction Force (PFJRF)(From The Patella: A Team Approach, reproduced with permission)37

__________________________________________________Chapter 2Figure 3 Diagram of contact areas from full knee extension to full flexion(From, Clinical Orthopedics 1975; 107, reproduced with permission)2.3 Patellofemoral Pain SyndromeMany texts describe PFPS as 'multifactorial', which reflects the difficulties not only ofdiagnosis but also in selecting appropriate treatment modalities 1;45 . PFPS is reportedto affect 25% of the general population at some time, although interestingly, there is adisturbing lack of hard demographic evidence for such a statistic. In a sports injury cliniccontext, patellofemoral pain was diagnosed in 137 out of 549 knee injuries (25%) 27 .More recent prospective studies have been conducted which have shown a 9%incidence over 2 years follow up in an athletic population 46 and 15% incidence over 14weeks military training 47 .38

__________________________________________________Chapter 22.3.1 NomenclatureFor many years, patients who presented with PFPS were given the diagnosischondromalacia patellae (CMP). CMP is a clearly defined clinical syndromeaccompanied by macroscopic softening, fissuring and fragmentation of the articularcartilage of the patella 48 . This diagnosis can only be made by direct visualisation byarthrotomy or arthroscopy 4 or by magnetic resonance scanning with the largest ordeepest of lesions 49 . Grelsamer & McConnell 50 outline in some detail the evolution ofthis term from the mid 1920's up to beginning of 21 st century. It was in the 1970's thatthe advent of arthroscopy allowed easier viewing of the articular surfaces andsurgeons were reporting that many of their patients with patellar pain and diagnosedwith CMP had normal articular cartilage, and some patients found to havechondromalacia had no patellar pain 35;51;52 .Some authors have branded CMP a 'wastebasket' term 33;46 , and although it recursoccasionally this term has largely been superceded by ‘anterior knee pain (AKP)’.More recently ‘PFPS’ has also become common usage, mainly thanks to authoritiessuch as Radin 53 , who highlighted these discrepancies and called for a specificdiagnosis.2.3.2 AetiologyTria et al. described four schools of thought to explain the symptoms commonlyassociated with PFPS: Patellar malalignment; quadriceps dysplasia; excessivelateralisation and fourthly, biochemical sequences 3 . Present day authorities from both39

__________________________________________________Chapter 2the orthopaedic and physiotherapy worlds seem to relate PFPS to patellarmalalignment and have even designed algorithms for treatment based on thispremise 50;54 . Some form of patellar malalignment is purported to be present in thevast majority of patients with insidious non traumatic patellar pain with the exceptionof young teenagers 50 . Malalignment will lead to the dynamic problem of patellarmaltracking, in which the patellar can be seen or felt to be moving incorrectly duringflexion and extension of the knee. Normal tracking will lead to normal alignment as aresult of balanced soft tissue restraints and good dynamic quadriceps strength andco-ordination 54 . Despite patellar malalignment being accepted as an aetiologicalfactor for PFPS, the cause of the malalignment is less well accepted. Consequently,there are other commonly cited causes of PFPS malalignment that must beinvestigated prior to selecting quadriceps rehabilitation as a first line treatment. Thislack of consensus is in itself a typical feature of this condition with authorities inrehabilitation selecting from the variety of theories proposed for patella malalignment.The common theories are:2.3.2.1 Abnormal foot pronationVarious investigations have used static goniometric 55 , kinematic 56 , kinetic 57 and evendynamic visual estimation 58to assess the position of the foot in general and thesubtalar joint in particular of patients with PFPS. All of these studies have establisheda relationship between either excessive or prolonged pronation and PFPS. This isdue to abnormal pronation causing a compensatory tibial external rotation. It has40

__________________________________________________Chapter 2been found that increased external tibial rotation (torsion) is associated with instabilityof the patellofemoral joint 59 . This is probably due to the tibial rotation causing patellamalalignment and torsional stresses at the knee normally a valgus vector force duringthe gait cycle 50 . Foot postural problems can usually be corrected through an orthoticdevice and lead to a reduction in PFPS symptomology 60 or retraining antipronatoryfoot muscles rather than those of the quadriceps 50 .2.3.2.2 Soft tissue tightnessIn general four muscles can cause biomechanical dysfunction with subsequentpatellofemoral malalignment. Tightness of any of the muscles listed can have anadverse effect of patellofemoral biomechanics 50 .• Rectus Femoris – tightness of the rectus femoris results in a lack of full glide inthe femoral trochlear during knee flexion.• Hamstrings – tightness of the hamstrings can increase the dynamic ‘Q’ angleresulting in lateral tracking of the patella.• Ilio-Tibial band – tightness of the Ilio-Tibial band causes lateral tracking andtilting of the patella and a resultant weakness of the medial retinaculum.• Gastrocnemius - due to its insertion above the knee joint this muscle can act asa weak knee flexor. Tightness, therefore, results in the same problems as thehamstring group.41

__________________________________________________Chapter 22.3.2.3 Proprioception dysfunctionRecently, it has been proposed that patients with PFPS may exhibit proprioceptivedysfunction. As yet the evidence is contradictory 61;62 and it has yet to be established ifthis is cause or effect. However, this new area of interest is worthy of furtherinvestigation as patellar taping has been shown to improve knee proprioception inhealthy subjects 632.3.2.4 Muscle imbalance and weaknessProbably the most intensive non operative research concerns the muscle activity ofthe quadriceps in general and the VMO and VL in particular. Unfortunately, this largebody of knowledge has produced considerable controversial debate surrounding therole of the quadriceps group in the aetiology and treatment of patellofemoral pain. Toexamine this role objectively electromyography (EMG) has been used by many authorsto assess the magnitude of motor unit activity of the quadriceps (‘activity’) and the timeof onset of contractions VMO and VL relative to each other (‘timing of onset’) 10;64-68 . Thelack of agreement amongst these authors has certainly contributed to discrepancies andmisunderstandings in clinical practice. For example, an imbalance of VMO activityrelative to VL is considered a cause of PFPS, yet is based on inconsistent evidence 10;69 .Similarly, differences in the timing of onset of contractions of the VMO and VL isregularly cited as a cause of PFPS, yet the evidence is disputed using a patellar tendonreflex testing apparatus. 68;70;71 . Powers et al. 11 , looking at both these aspects in onestudy, analysed performance of the quadriceps during more functional activities such as42

__________________________________________________Chapter 2stair climbing, level and slope walking. They showed there was neither imbalancedactivity nor asynchronous timing in any of the vastii but rather the patients with PFPSshowed a decrease in activity for both VMO and VL. This was confirmed by a later studyascending and descending stairs 72 .In terms of muscle weakness, there is evidence that patients with PFPS have weakerquadriceps than healthy subjects 30;73;74 . For example, when measured by isokineticdynamometry the knee extensors of a group of runners with anterior knee pain weresignificantly weaker than a control group of runners. Interestingly, the extensors of thenon painful knee were also weaker than the control group, indicating that generalisedquadriceps weakness was not just as a results of pain inhibition on the injured side butrepresented a bilateral deficit 8 .2.4 Quadriceps muscles2.4.1 IntroductionExercise is the most commonly chosen method of conservative treatment for PFPS withrehabilitation focussing on the quadriceps femoris group. This section aims to review theanatomy and role of quadriceps exercise in PFPS. It concludes that although exercisecan still play a major role in the treatment of this condition, the currently used exerciseregimes for this muscle group can sometimes increase symptomology if the regime isincorrectly adhered to or is too demanding for the patellofemoral joint.43

__________________________________________________Chapter 2When a diagnosis of PFPS has been made, conservative treatment often forms themainstay of management, with patients experiencing a favourable response rate of 60-80% 75 . Response rates of 95% have also been reported without firm statistics and withthe caveat that conservative treatment can mean either exercise, stretching, kneebracing, activity modification or medication either separately or in combination 3;76 . Ofthese treatment components the most important is thought to be exercise 77 , withquadriceps exercises in particular being employed 78 .There can be little doubt of the importance of normal quadriceps activity to the functionalintegrity of the knee joint. Lieb and Perry 78;79 describe the loss of terminal extension ofthe knee joint as indicative of general quadriceps weakness.In an attempt to correct the problem of generalised quadriceps weakness most texts ofPFPS have included instructions for general quadriceps exercises which usually consistof isometric, inner range (terminal extension or short arc), eccentric and straight legraise exercises. Different studies advocate widely varying weight resistance andrepetition rates. Although the aim of these exercises is said to be quadriceps'strengthening,' present knowledge casts doubt on the accuracy of such a statement andthe value of some of these exercise regimens.2.4.2 AnatomyThe quadriceps femoris is the only muscular group that causes extension of theknee 80 . It is comprised of four heads: rectus femoris (RF), vastus medialis (VM),vastus lateralis (VL) and vastus intermedius (VI)(Figure 4). These four muscles44

__________________________________________________Chapter 2converge into a common tendon that crosses the knee joint, envelopes the patella ina multilaminar fashion and inserts into the tibial tuberosity. A contraction of any ofthese components will cause knee extension. The four components also equaliseeach other medially and laterally to cause central alignment of the patella in thefemoral groove during knee extension (Figure 5). RF originates from the anteriorinferior iliac spine and from just above the acetabulum. Thus, it is the only muscle ofthe quadriceps crossing two joints and when contracted causes hip flexion and kneeextension simultaneously.VI lies directly anterior and lateral to the shaft of the femur. Its fibres end in anaponeurosis that forms the deep part of the quadriceps femoris tendon 81 .The VM muscle has been described as having two parts; the vastus medialis oblique(VMO) and vastus medialis longus (VML)(Figure 6). These two components areseparated from each other by a fascial plane 82 containing a branch of the femoral nervewhich sub-divides to innervate both VMO and VML. The VML fibres lie at an angle of15 0 to the longitudinal axis of the femur. The fibres of the VMO lie at 40-45 0 to the sameaxis. The VMO receives the richest nerve supply of the quadriceps due to a distalwardincrease in the number of nerve fibres 83 . VM has also been described as having atripartite arrangement of upper, middle and lower fibres 83 , though the bipartitearrangement described above is more generally accepted.45

__________________________________________________Chapter 2Figure 4 Cross section of the quadriceps femoris muscle group(from Gray’s Anatomy, reproduced with permission)VL muscle has also been described as having two parts 82 . The proximal fibres form thevastus lateralis longus (VLL) while the distal and more horizontal fibres form the vastuslateralis oblique (VLO). An areolar fascial plane separates the two, but both sectionshave the same nerve supply. The VLL inserts into the base of the patella but the VLOthat is said to originate from the iliotibial tract and the intramuscular septum inserts intothe lateral margins of the patella. The VML and VLL are seen to cross each other as anaponeurotic expansion in front of the quadriceps tendon. Unlike VM the two componentsof VL are generally considered to function as one integrated unit.46

__________________________________________________Chapter 2Figure 5 Direction of pull of the Quadriceps(from: The Patella: A Team Approach, reproduced with permission)2.4.3 Methods of Quadriceps exercise.There is a variety of exercises employed to rehabilitate the quadriceps muscles andall are used in some form for patients with PFPS.• Firstly, isometric exercise that has been found to neither selectively fatigue the VMOmuscle 84 nor selectively exercise it 26 .• Secondly, inner range (also known as short arc or terminal extension exercise) thathas been shown to have equal EMG activity 64 of the VMO and VL.47

__________________________________________________Chapter 2• Thirdly, the straight leg raise. Despite the relatively small activation of thequadriceps with straight leg raise, exercise regimens employing this activity (15minutes, four times daily) over three months resulted in an increase in EMG activityfor all quadriceps components tested 69 . This increase in EMG activity wasaccompanied by some improvement in PFPS symptoms but the authors proposedthat this may not be the most effective form of training for this syndrome.Figure 6. Anterior view of the superficial quadriceps femoris.48

__________________________________________________Chapter 2The three commonly used methods above have been described as Open Kinetic Chainexercises (OKC) as defined by Steidler 85 . Closed Kinetic Chain (CKC) exercises existwhen neither the proximal nor distal segments are free to move due to externalresistance e.g. a squat 86 . The use of CKC exercises 87;88 has been proposed as a morefunctional method of rehabilitation in PFPS 89;90mainly because of the role CKCexercises are said to have in training the quadriceps eccentrically and their role in coordination91 .An additional method of rehabilitating the quadriceps is to use eccentric exercise. Dviret al. 73 found a significant (p

____________________________________________________________Chapter 3Chapter 3ELECTRICAL STIMULATION50

____________________________________________________________Chapter 33 ELECTRICAL STIMULATION3.1 IntroductionAs stated in section 1.2 ever since methods of generating and storing electricity werefirst discovered in the 1740’s there has been considerable interest in the role thatelectrical activity plays in treating illness 18 . This chapter now continues to summariseone particularly important area of research, namely that of quadriceps musclerehabilitation and attempts to summarise the findings in this increasingly complexarea. Computerised searches were carried out from 1996 to the end of September2001. Databases included Medline, Winspirs Silver Platter Information RetrievalSystem, Excerpta Medica, Cinahl, and Physiotherapy database. Key words forsearching included quadriceps, muscle, stimulation, electrical, electricity,rehabilitation, femoris, vastus medialis, and vastus lateralis. The search was limited toEnglish language journals. Additional searching was undertaken using referencesfrom existing reviews in the field and from publications obtained from electronicsearching. The criteria for inclusion of a study in the review were original researchonly, no reviews; only stimulation over a treatment period of days or weeks but noacute stimulation within one stimulation period; no functional electrical stimulation ortreatment for paraplegia.51

____________________________________________________________Chapter 33.2 Electrical stimulation of animal muscleInvestigations on animals have provided useful information on the effects of EMS at acellular level. Studies involving chronic low frequency stimulation (i.e. 10Hz, 24hoursdaily for several weeks) have shown that it affects the major functional elements ofthe muscle fibre such as the calcium (Ca 2+ ) regulatory system, the myofibrillarapparatus, energy metabolism and the microvascular system 92 .3.2.1 Calcium regulatory system changesCa 2+ is released from the sarcoplasmic reticulum into the myoplasm in response toexcitation of the sarcolemma and T-tubules by a nerve impulse. This excitation canbe either natural (voluntary contraction) or artificial (electrical stimulation). 48 hours oflow frequency EMS can result in significant decreases in the initial rate and maximumcapacity of Ca 2+uptake in the sarcoplasmic reticulum. These changes becomegreater with longer stimulation and are accompanied by decreases in the activity ofCa 2+transport ATPase 93 . There are also transformations in the sarcoplasmicreticulum to that resembling slow twitch muscle including a decrease in calsequestrin(the major binding Ca 2+ protein of the sarcoplasmic reticulum) and an increase inphospholamban (a protein normally only present in slow twitch fibres and cardiacmuscle) 92 . These changes correlate well with ultrastructural changes such asdecreases in the number of T-tubules, terminal cisternae and the longitudinalsarcoplasmic reticulum 92 . Interestingly, these changes at the cellular level return tofast twitch muscle levels 2-4 weeks after cessation of stimulation 94 .52

____________________________________________________________Chapter 33.2.2 Myofibrillar apparatus changesThe slowing of a contraction induced by chronic low frequency EMS results fromalterations in the Ca 2+dynamics and subsequently from changes in the myofibrilapparatus from fast to slow characteristics. These include ultrastructural changessuch as widening of Z bands (thus resembling slow twitch fibres) and a significantdrop in weight and CSA although the total number of fibres is retained 93 . It alsoseems that chronic stimulation leads to a thorough rearrangement of the myofibrillarproteins (troponin and tropomyosin in the thin filament and myosin in the thickfilament) in the sense of a fast to slow transformation of the sarcomere 92 .3.2.3 Energy metabolism changesThe increase in contractile activity imposed on fast twitch glycolytic muscle fibres,which are only intermittently active during normal locomotion, causes an increaseddemand for enhanced energy supply. Because fast glycolytic fibres are not usuallyexposed to sustained activity, the muscle moves from anaerobic to aerobicmetabolism to meet this demand 93 . Therefore there are important alterations in theenzymes of the energy supply in the muscle undergoing chronic stimulation.There are also important vascular changes concurrent with this. It has been notedthat there can be a 5 fold increase in capillary density with a marked elevation in theaerobic-oxidative capacity in fast twitch muscle from chronic low frequency EMS 94 .These vascular changes are dramatic enough to be observed even by the naked eyeas fast twitch muscles (e.g. the rabbit tibialis anterior) change to the deep red colour53

____________________________________________________________Chapter 3associated with oxidative muscle characteristics 92 . Capillary density (i.e. the numberof capillaries per area) is achieved probably as a result of an increase in the numberof capillaries and a decrease in the muscle fibre diameter, both of which occur afterchronic low frequency stimulation. This has the effect of improving the oxygen supplyto improve the oxidative changes in activity.3.2.4 Neurogenic changesIn contrast to the plethora of work to observe metabolic, vascular, myofibrillar andcellular changes in muscle after chronic stimulation, there has been very little work onthe neural changes results from stimulation. The only published work in animals hasbeen concerned with nerve damage arising from chronic stimulation in preparation ofphrenic nerve stimulation on humans 95 . Some experts have speculated that theremay be some changes in the nerve due to the antidromic nature of the stimulus andthat there may be some adaptive changes to the nerve due to the increasing numberof action potentials being delivered by a stimulator, but as yet there is little or noevidence (Jarvis, personal communication 2002).3.2.5 SummaryThere seems to be irrefutable evidence in the animal model that EMS causes anadaptive change in a muscle’s normal pattern of use and that the changes underlyingthis response involve every aspect of the metabolic, circulatory and energy systems 96 .54

____________________________________________________________Chapter 3This physiological basis for EMS is a basis to exploring its efficacy both in terms ofphysiological changes observed in the muscles and functional outcome as measuredby handicap, impairment and disability in humans. The next sections review the roleof EMS in both healthy subjects and those with weakened quadriceps muscles.3.3 Electrical stimulation of human quadriceps muscleConsiderable debate has surrounded the role of EMS in increasing normal humanquadriceps muscle strength. Many papers cite the work of the Russian investigatorKots, who reported that EMS techniques could produce a 30-40% increase in musclestrength in already highly trained athletes 97 . This section considers a number of otherinvestigations that have attempted to replicate these observations in healthyindividuals. Unfortunately, it is difficult to come to any firm conclusions from thesepublications. Whilst some authors have compared EMS with exercise 31;32;98-114 , othershave compared different types of EMS with each other 115 116;117 or had no control orcomparison group at all 118-123 . Even within each of these groups of papers EMSregimes, methodological approaches, outcome measures and many other variablefactors made direct comparison impossible. It is against this background that thedrawn conclusions in this section are discussed.55

____________________________________________________________Chapter 33.3.1 Quadriceps Strength3.3.1.1 EMS or isometric exerciseTable 1 summarises the results for strength/torque changes described in sixpublications that compared isometric exercise with EMS. Only Mohr et al. 103 foundsignificant improvements in isometric quadriceps muscle strength with isometricexercise (14.7%, p

____________________________________________________________Chapter 3Table 1. Comparison of strength/torque gainsbetween isometric exercise and electrically stimulated groups.Author Average %improvement instrength gain forexercise group.Kramer &19% 13%Semple 100Average %improvementsin strength gainfor EMS group.12% EMS&ExBetween groupstatisticalcomparisonsp= 0.256Laughman et al. 101 18% 22% NSS P value not statedMcMiken et al. 102 25% 22% p> 0.05Mohr et al. 103 14.7% 0.7% p< 0.05Kubiak et al. 107 43% 33% p> 0.05Caggiano et al. 109 10% 8.5% p= 0.7593.3.1.2 EMS or isokinetic exerciseTwo studies directly compare isokinetic exercise regimes with faradic EMS in healthyquadriceps 99;105 . Improvements in quadriceps power have been described for bothstudies though one case 99 was only able to provide a descriptive improvement (42%for the exercise group, 22% for the stimulated group), due to the small number ofsubjects in each group. Interestingly, Nobbs & Rhodes 105 only describeimprovements in strength at velocities equal to or slower than the exercise trainingvelocities i.e. 30 0 /s or 0 0 /s with no significant differences at angular velocities of100 0 /s or 180 0 /s. When results are re-calculated to reveal absolute percentagechanges the stimulated group, when treated isometrically at 45 0knee flexion,57

____________________________________________________________Chapter 3displayed percentage improvements of 29%, 11%, 9% and 1% at angular velocities of0 0 , 30 0 , 100 0 and 180 0 /sec respectively.3.3.1.3 EMS and isometric or isokinetic exercise combinedA number of papers have attempted to describe the combined effects of EMS whilstperforming voluntary exercise. All papers agreed unequivocally that a combination ofEMS and exercise simultaneously is no more effective than exercisealone 105;106;108;110;124;125 . Further more, this conclusion was arrived at irrespective ofwhether the exercise regime was isometric or isokinetic. It would, therefore, appearthat there is nothing to be gained from combining these two forms of intervention inhealthy quadriceps. One explanation proposed was that subjects reliedsubconsciously on the EMS current for extra effort towards a maximumcontraction 125 .Conversely, Strojnik 126used a single test laboratory protocol withsubjects performing an isometric contraction at 45 oknee flexion, an isotonicconcentric activity from 90 o to full knee extension and a squat jump with and withoutEMS. He found that superimposed 0.8 s 100Hz EMS improved isometric torque by23% and isotonic torque by 4% of baseline measures, but did not alter the morecomplex multi joint activity of squat jumps.58

____________________________________________________________Chapter 33.3.2 EMS at varying knee flexion anglesThe example from Nobbs and Rhodes 105 in section 3.2.1.2 above raises interestingquestions as to whether training with EMS at one angle of knee flexion can influencestrength gains at other angles. This section of the review looked at this as a possibleconfounding variable in assessing muscle function.3.3.2.1 Isometric strength gainsIn the majority of cases the knee angle adopted for EMS was the same as thatassumed during testing. A standardised position of 60 0 knee flexion was described bymany authors 32;98;100;101;103;107;109;110;113;121 . Other authors cited different angles rangingfrom 15 0 to 90 0 knee flexion 118;119 . In all cases hip flexion, if mentioned, was keptconstant for both treatment and assessment positions. When multiple angles wereinvestigated, the improvement in strength occurred nearest the test angle 127 . Table 2summarises the percentage strength/torque gains over the range of knee flexionangles studied and Table 3 the parameters used. Each of these studies describesstatistical improvement in quadriceps isometric muscle strength, although the rangeof results is quite varied (1 – 49.7%) and probably due to the wide diversity inmethodological approachs and stimulation regimens. An improvement in isometric butnot isokinetic strength following EMS has been noted on the dominant leg of healthysubjects using 50Hz on an alternating 2000Hz frequency 111 , but these authorsconceded that their study had low power (1-β ranged from 0.24-0.45) due to a smallsample size. Furthermore, although the increases in isometric strength were59

____________________________________________________________Chapter 3“impressive” and statistically significant (P < 0.05) they doubted the value of EMS insupplying the force needed for motor skills (as assessed isokinetically at 30 0 /s and60 0 /s), although it is helpful when normal movement is hampered.3.3.2.2 Isokinetic strength gainsIn contrast to the above studies where the muscle was stimulated and testedisometrically at the same angle of knee flexion, other studies have considered theeffects of stimulation and knee position on isokinetic function. Hartsell 104 stimulated at65Hz an isometrically constrained quadriceps muscle while the subject was in thesupine position with the knee flexed at 20 - 30 0 , but tested quadriceps ‘dynamicstrength’ (30 0 /sec) and ‘muscular power’ (180 0 /sec) throughout an active range ofmotion of 90 0 to 0 0 knee flexion. Only a minimal increase in isokinetic values at bothvelocities was reported. Halbach and Straus 99 stimulated an isometrically constrainedquadriceps muscle at 45 0 knee flexion. Quadriceps strength was tested isokineticallyat 120 0 /s throughout a range of motion of 90 0 to 0 0 . This study described an averageimprovement in isokinetic strength of 22%. The two studies cannot be compareddirectly due to the large number of methodological differences between them. Therewas only paper within this series that did not train isometrically and testisokinetically 112 . Fahey et al. 112 looked at the effect of knee angles 0 0 and 65 0 duringstimulation training. on healthy subjects. They concluded that EMS at 2000impulses/min was more effective at increasing isokinetic, but not isometric, musclestrength if the knee was flexed at 65 0 . No explanation could be offered for this finding,60

____________________________________________________________Chapter 3but they speculated that the improvement was due to either a stretch stimulus appliedto the quadriceps at 65 0 , or (similar to Nobbs and Rhodes’s 105 explanation) due togreater tension within the quadriceps during the stimulation at 65 0 knee flexion.61

____________________________________________________________Chapter 3AuthorTable 2. Percentage strength / torque gainsover a range of knee flexion treatment and assessment angles.Treatmentangle (kneeflexion)Assessmentangle (kneeflexion)improvement % MVIC P valueKramer &60 o 60 o 13% Max. Tol. p

____________________________________________________________Chapter 3Table3. Comparison of Electrical Stimulation Parameters and delivery.Monopolar Max.author waveform intensity frequency duty cycle sessions improvementHalbach &50Hz 10:50:10 15 22%Straus 99 toleranceKramer and Monoasymm Average Not stated 10:50:10 10-12 13%Semple 100 biphasic 87%MVCLaughman et Monosymm 80% 50Hz * 10:10:10 12 44%MVC5% MVC 25Hz* 10:50:10 28 13.2%25%MVC50%MVCMax.tolerance50%MVCMax.25Hz25.3%50Hz 5:5:30 15 24.2%48.5%Balogan et al 117 Monophasictwin peak20Hz45Hz80Hz10:50:10 ? Average 24%all groupsSoo et al 121 Mono symm50Hz* 15:10:8 10 47.7% menbiphasic8.1% womenSt Pierre et Bi symm50Hz* 10:50:10 7 not statedal. 120Biphasic toleranceObajuluwa 119 Mono Max. surged 3:10:10 30 49.7%asymm tolerance faradicbiphasic* = on a modulated frequency of 2500Hz63

____________________________________________________________Chapter 33.3.3 Gender differences and strength improvementOne further observation made by Soo et al. 121 is that men displayed greater strengthimprovements after EMS than those of women (47.7% compared with 8.1%),although no physiological reason for this was given. Fahey et al. 112 on the other handshowed no sex differences in electrically stimulated strength increases. It seemsunlikely that men perform differently from women in this respect. Indeed Soo et al. 121suggest their results are the likely result of an arbitrary division of subjects by sexresulting in a small sample size (9male and 6 female) rather than a real sexdifference.3.3.4 Quadriceps enduranceThe effects of EMS on the endurance of healthy quadriceps have been considered onfew occasions 31;115;118;123 . Eriksson et al. 118 described endurance as the time taken fora sustained maximal voluntary isometric contraction (MVIC) to fall to 50% of the initialvalue. Nine subjects were stimulated with uniform 100Hz for 4-5 days over 5 weeks.Karba et al. 31employed a more elaborate measure of endurance. This involvedstimulation of the muscles for two 10 second sustained contractions at 20 and 100Hzrespectively. The measure of fatigue (a Fatigue Index) was taken as a ratio of theproportion of the area under the isometric curve (i.e. total force) during the first 3.33seconds compared to the whole 10 seconds of the contraction for each frequencyrespectively. Both these studies recorded no change in endurance irrespective of the64

____________________________________________________________Chapter 3osteoarthritic patients, defined endurance as the time taken to fall below 90% of initialMVIC. Endurance results from this study showed that non uniform random and PNMSstimulation were superior to sham and uniform EMS.The reasons put forward for those results and indeed the premise for that study werethat patterned stimulation, in contrast to existing EMS devices, delivered a morenatural firing pattern that addressed both the strength and endurance components ofthe muscle.The limited number of studies in this area suggest that further research on humans isnecessary. Animal physiology experiments formed the basis for the endurancehypotheses in humans and so were technically outwith the remit of this review.However, a recent study showed that low frequency (10Hz) stimulation of a rabbit’stibialis anterior for as little as 30 minutes daily for 6 weeks resulted in a substantialincrease in the endurance capacity of the muscle 128 .3.4 Electrical stimulation of weak quadriceps muscle3.4.1 Changes in isometric and isokinetic strength.Despite experiments on healthy quadriceps allowing insight into the effects of EMS onmuscle, care should be taken when extrapolating the results to a pathologicalcondition with concomitant quadriceps weakness 129 . Indeed the literature suggeststhat there are a number of considerations such as pain, effusion and inhibition whenusing EMS on weak as distinct from healthy quadriceps. Furthermore, the effect of66

____________________________________________________________Chapter 3EMS is influenced to a large extent by the degree of limb injury or immobilisation andthe resulting muscle weakness 130 . Consequently, EMS as used for a rehabilitationprogramme for various knee pathologies has been thought to minimise 131 , improve 129or have no effect 130on muscle weakness as measured by isometric or isokinetictorque of the quadriceps.For example, in the period of lower limb immobilisation after anterior cruciate ligament(ACL) reconstruction, isometric quadriceps torque was found to be diminished over a6 weeks period by 60% after EMS of 500 impulses/min for 8 hours daily compared to80% in a control group 131 ; decreased after 6 weeks by 39% after 40 minutes EMS 3times weekly compared to 58% for controls 132 ; or demonstrated no significantdifference between the two groups despite 8 hours of daily stimulation for 6 weeks at800 impulses /min 133 .The differences between these studies is due to the smallsample sizes and their varied EMS regimes and methodology.Non-immobilisation regimes post ACL reconstruction have also advocated EMS aspart of the rehabilitation protocol. Delitto et al 134 . noted a 48% and 65% increase inMVIC of quadriceps and hamstrings respectively in the initial treatment phase afterstimulation of both these muscle groups in an ‘ABAB’ designed single case study.Later work by the same group 129 observed statistically significant (p

____________________________________________________________Chapter 3performed an ‘ABAB’ cross over experimental design of exercise alone or exerciseand EMS combined. Although there were significant within group differences, theyfound no differences in the mean strength changes between the two groups, probablyresulting from the small sample size.Isokinetic strength was measured by Snyder-Mackler et al. 135 in a comparison of fivepatients after ACL reconstructive surgery using active exercise alone and five using acombination of active exercise and EMS. For example, at an angular velocity of 90 0 /sthe average and peak isokinetic quadriceps torque improvement, normalised to theuninjured leg, were 44 and 43% in the exercise group, but 70% and 69% respectivelyfor those who had EMS additionally. In other words, adding 4 weeks of EMS at 1,250impulses/min 3 times a week to voluntary exercise saw a statistically significant(P

____________________________________________________________Chapter 3torque were observed within all groups with no significant differences between thesegroups. However, a lack of a comparative control group and a small sample size wereof concern in this study.The long term effect of EMS compared to voluntary exercise was analysed by Lieberet al 139 . Assessment of MVIC took place 6, 8, 12, 24 and 52 weeks post ACLreconstruction. At all stages and within all groups there was an increase in the MVICthat was not significantly different between the groups. This study carefully matchedeach week the number of contractions for the voluntary exercise group and the EMSgroup (which received 1000 impulses/min for 30 mins 5 times a week for 4 weeks)and under these circumstances there seemed to be no advantage gained from EMS.Furthermore, this work highlighted the problems encountered by previous studies incomparing EMS with voluntary exercise and recommended controlled ‘treatmenttension’ of the muscle to resolve these potential discrepancies.A further concern arising from the studies cited was the problem of defining maximaleffort of quadriceps contraction during MVIC assessment. To overcome this, themethod of twitch interpolation has been advocated to ensure maximal effort 140;141 .Only two studies utilised this method in the context of evaluating EMS of thequadriceps 115;142 . Oldham et al. 115found no difference in maximum voluntaryisometric torque (MVIT) after 10Hz stimulation compared to a placebo group inosteoarthritis knee. This study found no differences between sham, uniform,patterned and randomised pattern stimulation groups. Snyder-Mackler et al. 142 used“high intensity” EMS (2500Hz carrier frequency modulated at 50Hz) for the69

____________________________________________________________Chapter 3quadriceps rehabilitation post ACL reconstruction compared to a group receivingexercise, another with “low intensity” EMS (55Hz) and a final group receiving acombination of “low and high intensity” EMS. They observed that quadriceps strengthaveraged 70% or greater than that of the contralateral limb after “high intensity” EMSwith only 57% after high volitional quadriceps exercises and 51% after “low intensity”EMS.3.4.2 Electrical stimulation in PFPSThere is a paucity of studies that have observed the effect of EMS on muscle strengthin patients with PFPS. Williams 143 , in a poorly described study, provided no measureof muscle strength to explain his remarkable success rate of 97 out of 100 subjectswith CMP being symptom free after treating the quadriceps with faradic EMS.Johnson et al. 144 the so called ‘russian stimulation’ also failed to provide any raw datato elucidate their 200% isometric quadriceps strength improvement in five patientswith ‘severe’ and 25.3% improvement in 30 patients with ‘mild’ CMP. Horodyski andSharp 145 produced a conference abstract with OKC isometric measures at variousknee angles and OKC isokinetic measures at a variety of angular velocities on 21female PFPS patients. They noted a significant (p < 0.05) increase in peak torque inall tests when comparing “high frequency sinusoidal” MS alone to EMS combined withquadriceps exercises. Once again, no raw data was presented in this abstract.Werner et al. 30 tested in OKC isokinetic mode at 60 0 /s and 180 0 /s in a more robuststudy of 40 Hz EMS of 1,400 impulses/min for 40 mins daily for 10 weeks on the70

____________________________________________________________Chapter 3quadriceps of 30 PFPS patients. They noted modest within velocity improvements of5.9% at 60 0 /s and 6.1% at 180 0 /s. They attributed the significant (p < 0.01) increaseat 180 0 /s to preferential activation by the EMS of quadriceps type 2 muscle fibresmore than type 1, which is a reversal of activation patterns in normal voluntarycontractions. Unfortunately, this uncontrolled (neither placebo nor comparative) studywas confounded by a daily stretching routine for the lateral thigh structures during the10 weeks treatment programme. This is an activity that, in itself, can have profoundbeneficial effects on muscle physiology 146 .3.5 Other muscle changes due to EMS3.5.1 Histology and BiochemistryThe use of muscle biopsy has provided evidence of the cellular changes from EMSon human muscle particularly the quadriceps muscle. In the healthy quadricepsEriksson et al. 118 demonstrated that muscle fibre area and fibre type compositionremained unchanged with 200Hz EMS. St Pierre et al. 120 , on the other hand (workingwith Kots and using his EMS protocol of “russian“ stimulation of 2,500Hz modulatedat 50Hz) described a significant decrease in fast twitch type 2 fibre area (in men only),but no change in fibre type distribution. This observation was supported by Delitto etal. 122 who used similar EMS protocols and also noted a significant decrease in type2a and 2b fibre area, with a concomitant increase in Type 1 fibre area. They alsonoted an increase in type 2 fibre type. Neither of the authors was able to explain the71

____________________________________________________________Chapter 3contradiction of high frequency EMS causing fast twitch fibre area reduction but anincrease in fibre type and an increase in slow twitch fibre area. The reduction in fibrearea post stimulation in healthy subjects contrasts with that observed post stimulationin patients following knee injury 132 . This suggests that the mechanisms involved instrength training for healthy subjects compared with subjects with muscle atrophy areentirely different. In healthy subjects neural factors or enzymatic changes may bemore important than fibre type changes. Few papers describe in detail muscleenzymatic changes associated with EMS in healthy volunteers. Eriksson et al. 118observed no significant changes in enzyme activity involved in the contration processalthough the same group also reported, on patients after five weeks of knee andquadriceps immobilisation, a decrease in succinate dehydrogenase activity (a markerof mitochondrial oxidative activity) that was significantly retarded after EMS 147 . On theother hand an uncontrolled study of eight healthy volunteers 123 observed a significantincrease in aerobic oxidative enzyme activity but no change in anaerobic markersafter 8 weeks chronic low frequency EMS (8Hz for 8 hours per day) of the quadriceps.It is important that the different findings reported by various studies are related todifference in EMS parameters. For example, the last cited study 123used 8Hzstimulation with a duty cycle of 55son and 5s off giving a total of 440 impulses/min. Incontrast, the most recent work on healthy human vastus lateralis phenotype afterEMS found that short bouts (30m per day, 3 days a week at 45-60Hz, delivering aminimum 1620 impulses/min) increased the percentage of type 2a fibres whereaspercentage of other fibres types all decreased. The histological and metabolic72

____________________________________________________________Chapter 3changes were not reflected in changes in the whole body indicators of aerobiccapabilities of the untrained subjects, nor the neuromuscular performance of thequadriceps, nor by muscle fibre hypertrophy 148 .In the atrophied quadriceps, a significant decrease in the muscle enzymes levels ofcitrate synthase and triphosphate dehydrogenase was shown in a control exercisegroup but not in a group receiving EMS 132 . Chronic muscle ewasting is associatedwith a decrease in muscle protein synthesis and Gibson et al. 149 found muscle proteinconcentration and fibre diameter of the quadriceps group of an osteoarthritic kneewas maintained with EMS delivered at 400 impulses/min with no difference in the rateof muscle protein synthesis compared to a control group. They interpreted theirresults as a 45% increase in muscle protein volume concentration relative to thedecrease in the control group. This study followed earlier work by the same group onimmobilised lower limbs after tibia fractures 150 that also found that the same EMSregime maintained quadriceps muscle protein synthesis. Vinge et al. 151 found that thetotal concentration of ribosomes (a measure of protein synthesis) in vastus lateraliswas less reduced after EMS at 600 impulses/min to the quadriceps in patients whowere immobilised after abdominal surgery. Stanish et al. 152 found little decrease inATPase activity (an indicator of aerobic muscle activity) using an unspecified EMSregime after 6 weeks immobilisation post knee surgery.Detailed analysis from muscle biopsy of immobilised vastus lateralis has found nodifferences between 40Hz EMS at 1000 impulses/min and control groups in fibre areareduction 153 . Fibre type analysis in this study also found no significant differences in73

____________________________________________________________Chapter 3type 1 fibres and a non significant 5% reduction in type 2a in all immobilised patientsin all experimental conditions. Martin et al. 154 found that after total knee replacementboth 30Hz EMS (90 mins daily for 7 days) to the quadriceps and continuous passivemotion had no influence on the percentage of type 1 and type 2 fibres in vastuslateralis compared to continuous passive motion alone. Fibre CSA on the other hand,showed that EMS in addition to continuous passive motion significantly attenuatedfibre atrophy relative to pre surgery levels. Wigerstad-Lossing et al. 132 observed that,relative to type 2, the area of type 1 fibres was unchanged in a 30Hz EMS groupreceiving 750 impulses/min but was significantly reduced in an immobilised controlgroup. The actual percentage, therefore, of type 1 fibre was unchanged in bothgroups. Therefore the ratio of type 2/1 fibres increased in the EMS group indicatingthat there was an increase in type2 fibre type.In summary, there is evidence that EMS can cause changes at the cellular level ofmuscle physiology, notably maintaining protein synthesis in atrophied muscleresulting from immobilised limbs.3.5.2 Functional MeasurementsOne problem with EMS delivered to healthy subjects or athletes is that it is mostcommonly applied to the muscle isometrically which is generally not applicable tosports performance 108 . Therefore one purpose of studies assessing functionalparameters and dynamic movements is to observe how they are affected by EMSrather than the more common isometric or isokinetic outcomes. The high intensity74

____________________________________________________________Chapter 3‘russian’ stimulation regime employed by 155 after knee ligament trauma improved theirathlete’s vertical jump test to 89% of the healthy leg one week after removal of theplaster of paris. In the healthy athlete the improvements in performance are lessobvious.Venable et al. 108compared 50Hz EMS to a weight training group andobserved a 3% improvement in the vertical jump test for EMS but a 7% improvementafter weight training. They concluded that in term of functional performance there wasno benefit supplementing weight training with EMS. Contrary to this, Willoughby andSimpson 156found that supplementing weight training with a ’russian stimulation’protocol improved the vertical jump by 25% compared to 9% and 2% for weighttraining or EMS alone. They explained that this contrary result was due to using theEMS during both concentric and eccentric quadriceps contractions thus providingenough impetus to increase strength. Wolf et al. 106also described significantimprovements in vertical jump distance along with movement velocity, total work,power, and sprint time as a result of EMS when compared with controls. Absolutevalues are not described in this paper although Eriksson et al. 118 also described asignificant improvement (P < 0.01) in vertical jump height from 32cm to 40cmsuggesting that the changes they observed in isometric and isokinetic musclestrength could be translated into more complex functional movements.Functional analysis of the effect of EMS has been also been performed usingkinematic gait analysis. EMS of the quadriceps and hamstring groups after ACLreconstruction was found to improve walking velocity, cadence, stance time andflexion excursion of the knee 135 . This study concluded that the improvement of flexion75

____________________________________________________________Chapter 3excursion of the knee was directly and significantly correlated with strength of thequadriceps. Further research by the same group reported that high intensity EMS(2500Hz carrier frequency modulated at 50Hz) affected knee kinematics to bringabout a more normal gait pattern due to an increase in strength of the quadriceps 142 .3.5.3 Thigh GirthFive studies 99 104 105;111;119 described comparative measures of thigh girth before andafter a programme of EMS on healthy quadriceps. All five chose different positions totake their measures and all used a tape measure to make the assessment. Only onedescribed a significant improvement of 10.7% in thigh girth, though this was anuncontrolled study and lacked experimental rigor 119 . The remaining more rigorouspapers, described no change in thigh girth and would support the view that thigh girthof healthy muscle does not change with EMS.Thigh circumference using a tape measure has also been used when assessing thegirth of atrophied quadriceps even though this method has been criticised as aninaccurate method 157 . Taking this inaccuracy into account, the studies reviewed havearrived at the same conclusion as those using cross sectional area (CSA) asmeasured by computerised axial tomography (CT) or ultrasonography; muscle groupstreated with EMS demonstrate less loss of mass than their control groups 131;144;147;158 .Some authors noted an actual increase in thigh bulk 155;159and some noted nochange 122;160 , although one was a single case study 122 .76

____________________________________________________________Chapter 3CSA measurement is a more accurate method of evaluating atrophy of thequadriceps group and the studies reviewed reveal broadly similar results. CTscanning has shown significantly less wasting of the immobilised quadriceps groupafter EMS compared to a control group 132;150;153 . The same technique has been usedin PFPS to show a 6% increase in quadriceps CSA after EMS to the vastus medialis‘area’ 30 ; this study gave no actual figures of CSA measurements made nor of the pretestCSA.Vinge et al. 151 also used CT CSA to show that 30Hz EMS delivering 600 impulses/minfor 3 hours daily could retard the rate of muscle atrophy compared to the contralateralcontrol limb in 13 patients who were bed bound after abdominal surgery. Morerecently, Quittan et al. 161investigated the effect of 8 weeks of uniform 50Hzstimulation (800 impulses/min for 60 mins daily) at 25% MVIC to the quadriceps andhamstrings groups of bed bound patients waiting heart transplantation. They found a15.5% increase in the quadriceps CSA compared to a control group. Contrary tothese results, Oldham et al. 115 used compound B ultrasound scanning to observeCSA of the quadriceps in patients with osteoarthritis knee in a double blindassessment of patterned EMS. They found no change in CSA in any of the activeEMS groups compared to placebo.3.6 Stimulation parametersThe wide variation in stimulation parameters presents one of the major difficulties inobtaining any consensus about EMS. One of the most significant parameters is77

____________________________________________________________Chapter 3When considering other studies the picture becomes more confused. If a frequency of50Hz is taken for comparison, five papers describe the effects of this frequencydelivered on a (2,000 - 2,500Hz) sinusoidal carrier wave 101;107;120;121;165 . Changes inmuscle strength ranged from 0% 120to 47.7% 121 . This diversity in response wasmimicked by studies delivering a straight 50Hz stimulation without any carrier wave,recording a 0% 103 and a 48.5% 114 improvement in strength.3.6.2 Pulse durationThis is often erroneously called ‘pulse width’. Although pulse durations of longer than60 µsec are likely to recruit pain fibres, the longer durations set at 200 – 300 µsecproduce a more powerful contraction 164 . Pulse durations of 200 µsec have beenfrequently adopted in human studies in muscle 166 .3.6.3 Duty CycleThis is commonly referred to as the “on /off ratio”. The ‘on’ phase is the period inwhich a period of pulses is delivered to a muscle. The ‘off’ phase is the periodbetween sequential ‘on’ phases 164 . This parameter, along with frequency is importantto give the muscle a rest period between contractions and protect against prematuremuscle fatigue. The rate of muscle fatigue is markedly dependant on the duration ofrest periods between contractions 167-170 , A duty cycle with a short ‘on’ time and a long‘off’ time is useful in protecting against muscle fatigue and, consequently, enhancing79

____________________________________________________________Chapter 3osteoarthritis of the knee when stimulation intensities greater than 5% of maximumvoluntary isometric torque (MVIT) could not be tolerated 115 .Noel and Belanger 176 , comparing pain ratios in EMS and voluntary quadriceps musclecontractions of eight subjects, described maximum pain experienced with averagestimulus intensities of 47.1, 70.3 and 42.8% of MVIT for three stimulatorsrespectively. Many studies however, when incorporating quadriceps stimulationregimes, described stimulation levels set higher than these. For example, Currier &Mann 177 set levels to 67% of the MVIT whereas Sinacore et al. 178 set levels to 80% ofMVIT (see Table 3).In studies comparing the effects of EMS and exercise, changes in musclestrength/torque due to EMS alone ranged from 9% 109 to 33% 107 . Similarly, changesdue to exercise alone ranged from 9% 109 to 43% 107 (Table 1). One of the majordifferences between these two studies was in the intensity of muscle contractionachieved by exercise or EMS. Caggiano et al. 109 reported a level of activity for bothtreatment modalities that represented only 40% of MVIC (Table 3). Kubiak et al. 107however, reports an intensity level representing MVIC for the exercise group and amaximal tolerable level of stimulation (up to 75% MVIC) for the second group (Table2). Once again, this would suggest that the greater the level of activity and stimulationthe greater the strength gains. However it is not always the case that strength gainsare related to the intensity of a muscle contraction when different studies arecompared. Examples of this are the studies by Laughman et al. 101 and Lai et al 114(Table 3). In the former study the exercise group worked at an average of 78% MVIC81

____________________________________________________________Chapter 3but the stimulated group worked at an average level of 33% MVIC yet similar resultsfrom the two groups were obtained (18% and 22% increase in quadriceps strengthrespectively). In contrast, Lai et al. 114 comparing two intensities of electrically inducedmuscle contraction (25% and 50% MVIC) demonstrated significantly differentimprovements in muscle strength (24.2 and 48.5% respectively). This latter studywould suggest that providing the muscle contraction is induced by the samemechanism (i.e. EMS alone) the greater the intensity of contraction the greater theresulting strength changes.In the clinical environment, stimulation intensities need to produce a reasonablecontraction to effect change within the muscle whilst remaining acceptable to patients.Levels of 30% initial MVIT of stimulation have been described in a number of studiesinvolving the quadriceps and have demonstrated measurable muscle changes. Forexample, a stimulation level of 33% MVIT brings about strength gains of 22% 101 ; astimulation level of 25% MVIT brings about strength gains of 24.2% 114 . Suchstimulation intensities are tolerated by most patient groups. So for example, if the aimof early phase rehabilitation is to achieve a quadriceps recovery of 50% of the normalside, then the intensity should not drop below 10% and an average training intensityof 40% has been advocated in rehabilitation following ACL reconstruction 179 .Neverthless, the major limitation seems to be the amount of current that the patientcan comfortably withstand. This is dependant on skin resistance and capacitiveimpedance of skin 164 . This is an important consideration, as patients using stimulators82

____________________________________________________________Chapter 3with constant frequency trains of 35Hz or greater (about 100Hz) will encounterproblems trying to produce a forceful contraction comfortably at higher intensities.3.6.4.1 Length of TreatmentUnfortunately, not only were the effects of EMS difficult to review due to differences inthe intensity of the stimulation, but the treatment programmes reviewed variedconsiderably in terms of the amount of daily stimulation and the length of the full131;132 133experimental programme. A common treatment period was six weeks135;136;139;142;144;150;152;153;180 with some studies as short as 5 days 151 and others as longas 10 weeks 30 . There were no obvious correlations between length of treatment andimprovement in quadriceps strength or effect on atrophied muscle.Similarly, the weekly and daily repetition of EMS varied from 8 hours daily every dayfor 8 weeks 131 to 10 contractions every other day for 6 weeks 144 . Yet each of thesestudies with widely divergent protocols suggest that EMS could help retardquadriceps muscle atrophy or loss of strength.83

____________________________________________________________Chapter 3Table4. Frequency of EMS and effects on atrophied quadriceps muscleAuthors Knee pathology frequency Effects from EMSNitz & Dobner 155 Ligament strain 50Hz Increase thigh girthWigerstad-Lossing et al. 132 ACL Reconstruction 30Hz Decrease in rate ofquads strength lossSisk et al. 133 ACL Reconstruction 40Hz Non-Significant inquads strength EMSv exerciseDelitto et al. 134 ACL Reconstruction 50Hz Increase quadsstrength with EMS vexerciseDraper &Ballard 136 ACL Reconstruction 35Hz Increase quadsstrength withbiofeedback v EMSLieber et al. 139 ACL Reconstruction 50Hz Non-Significant inquadriceps strengthEMS v exerciseGould et al. 158 Disuse atrophy 35Hz Decrease in rate ofquads atrophyWilliams et al. 159 Post menisectomy 50Hz EMS worse thanexerciseArvidsson et al. 153 ACL Reconstruction 40Hz Decrease in rate ofquads atrophyGibson et al. 150 Immobilised fractured tibia 30Hz Decrease in rate ofquads atrophyIncrease quadstorque at 180 0 /secWerner et al. 30 Patellofemoral PainSyndrome40HzVinge et al. 151 Disuse atrophy 30Hz Decrease in rate ofquads atrophyGibson et al. 149 Osteoarthritis 30Hz Increase muscleprotein concentrationMartin et al. 154 Post arthroplasty 30Hz Decrease in rate ofquads atrophyHaug & Wood 181 Post arthroplasty 35Hz Non-Significant EMSv Continuouspassive motion84

____________________________________________________________Chapter 3an increase in power generating ability, high force (higher frequency) contractionsmust be generated within the muscle 167 . Results have been described from animalstudies 194comparing 2.5Hz with 10Hz EMS suggesting that 12 weeks chronicstimulation may increase force output without compromising the acquisition of fatigueresistance by increasing the amount of type 2a fibres.There have been few studies comparing different types of high and low frequencyEMS. In animals, Ferguson et al. 195 compared a 10Hz continuous to a 30Hz burstregime for 90 days. 30Hz EMS caused significantly greater preservation ofcontraction time and muscle mass but 10Hz EMS better preserved the index offatigue. This seemed to confirm the accepted viewpoint concerning high and lowfrequency EMS. In humans, Snyder-Mackler et al. 135compared 4 weeks of highfrequency EMS on a carrier frequency of 2500Hz modulated at 50Hz and what theytermed ’low’ EMS at 55Hz on patients following ACL reconstruction. Directcomparison of MVIC and kinematic analysis found no significant differences betweenthe two frequencies. A combined treatment protocol of 2500Hz modulated at 50Hzand 55Hz stimulation was significantly better than exercise and ‘low’ frequency EMS,and showed an average quadriceps strength improvement of 70% or greater than thecontrol. However, doubts should be cast on their definition of ‘low’ frequency at 55Hz.One of the few studies on the effect of chronic low frequency EMS on human muscleinvolved the gracilis muscle transplanted to form a neoanal sphincter 196 . Using thelow frequency techniques in animals of Salmons 197 , this group was able to convert a87

____________________________________________________________Chapter 3The ‘doublet’ phenomenon has also been demonstrated in studies on the humanquadriceps. Binder-Macleod & Baadt 202 investigated constant frequency trains at 70ms IPI and variable frequency trains with a short 1 st IPI (chosen from 5,10,15,20,30ms intervals) followed by an IPI of 70 ms. Results showed that 2 short IPIs resulted ina 64% augmentation of the force of fatigued quadriceps muscle than either 1 short IPI(32% improvement) or 3 short IPIs (29%). Karu et al. 208 investigated the quadriceps ofhealthy and spinal cord injured human subjects and concluded that the length of thefirst IPI should be approximately 5 ms with subsequent intervals limited to 20 ms tooptimise force output.EMS devices can now be programmed to deliver the naturally occuring firing patternsto muscle. This type of stimulation may prevent the problems previously associatedwith existing uniform patterns by preventing premature muscle fatigue associated withhigh aggregate numbers of impulses 209 . Furthermore, the initial large forces ofcontraction achieved with the ‘doublet’ may mimic the heavy resistance trainingeffective in strengthening muscle thus illustrating the power of this stimulation overprevious regimes 210 .Any new study should therefore use stimulation that has a simultaneous non uniformmixed pattern incorporating high and low frequencies and a ‘doublet’.92

____________________________________________________________Chapter 3the magnitude of changes in human quadriceps compared to animals appear to bemodest.Secondly, the use of a uniform pattern EMS has been questioned, when the literaturehas evidence that the normal physiological firing pattern for the quadriceps has a nonuniformed,mixed frequency composition. This has recently been further developed asa combination of high, moderate and low frequencies being delivered to the musclesimultaneously. It is the patterned non-uniform mixed frequency EMS, emulating thenormal physiological firing rates and frequencies of human muscle, that is beingadopted for the studies conducted later in this thesis.Therefore, it is proposed that a patterned non-uniform mixed frequency EMS (in thisthesis this has been named ‘RESTIM’*) will be more beneficial for the humanquadriceps than uniform fixed frequency pulse trains. These benefits may be manifestby improved muscle strength, function and pain but not at the expense of musclefatigue.* RESTIM is a working product title for the device and is not a trademarked name94

____________________________________________________________Chapter 4Chapter 4MEASUREMENT OFMUSCLE STRENGTH95

____________________________________________________________Chapter 44 MEASUREMENT OF MUSCLE STRENGTH4.1 IntroductionIt is commonly accepted that quadriceps weakness accompanies patellofemoral painsyndrome (PFPS). This has been confirmed by isokinetic assessment of PFPSpatients compared to control groups 73;74;211 . The presence of patellar pain not onlyconfounds the torque values but also has ethical implications for testing in isometricmode or at slow isokinetic angular velocities 212 . The studies cited above illustrate thatisokinetic assessment using isolated knee extension and flexion is the mostcommonly used method to assess strength* and function of the thigh musculatureand the knee. To this end reliability has been shown for the Biodex 213 the Cybex II 214and the KinCom isokinetic dynamometers 215 . However, isolated knee or single joint(SJ) testing may be undesirable or even contraindicated in some pathologicalconditions of the knee joint 216 . This may be due to differing muscle recruitment and forjoint and ligament stresses between multi joint (MJ) and SJ testing 217 and because ofquadriceps muscle inhibition during SJ testing 218 . Greater muscle isolation of thequadriceps in OKC testing has been shown to produce higher tibio- femoral jointshearing forces causing anterior tibial translation on the femur in the anterior cruciateligament deficient knee 219 and the normal knee 220 .The terms multi joint and single joint are rarely used in clinical practice. Usuallyclinicians employ the terms closed kinetic chain (CKC) and open kinetic chain (OKC)with their abbreviations based on the original work by Steidler 85 .* although the correct term is ‘torque’ this will be used interchangably with the term ‘strength’ to reflect clinical practice.96

____________________________________________________________Chapter 4Although the terms MJ and CKC are not interchangeable, several publications andjournals have used and continue to use the clinical terms. Due to the clinical aspect ofthis study, the following chapters will employ the OKC and CKC abbreviations.The effects of OKC testing on the patellofemoral joint have been studied by Nisell &Ericson 221 who showed that patellar compression forces were almost 12 times higherthan walking and six times higher than running at the most functional range ofmovement during isokinetic knee extension. They advised that patients with PFPSundergoing OKC isokinetic tests should only perform submaximal efforts which is atodds with the rationale of some testing procedures requiring a maximum contraction.However patellofemoral stresses during OKC testing can be reduced by using a CKCleg press exercise 222 . The improvement in perceived function in PFPS using CKCtesting 223 is thought to be due to the co-contraction of the biarticular muscles of thelower limb, proprioception, joint position sense and kinaesthesia 224 . It has beenproposed that the integration of all joints and segments in a movement such as kneeextension in standing is more preferable than an isolated motion of a OKC activitysuch as seated knee extension 86 .In terms of isokinetics, CKC testing is still a relatively new method of assessment anddata on its reliability and normative values are not yet available 225 . Dynamometerdata for CKC testing have been limited to isokinetic concentric leg extension torque 226or concentric/eccentric extension combining hip and knee activity 227 . Dvir 227compared isokinetic OKC and CKC findings, and although not analysing test-retestreliability found low and insignificant correlations between OKC and CKC lower limb97

____________________________________________________________Chapter 4tests. He concluded that total lower limb dynamic strength and quadriceps isolatedstrength could not be predicted by each other, thus highlighting the need for new setsof data on the CKC mode of testing. Lafree et al. 226 also compared isokinetic OKCknee extension to a CKC leg press movement. Using concentric extension peaktorque, reliability was examined in only 5 of the subjects, which revealed a ICC forseated leg press of 0.83 (SEM = 9.96) and supine leg press of 0.86 (SEM = 8.79).Levine et al. 228 found high ICCs of 0.85 – 0.94 on combined hip and knee concentrictests at angular velocities from 30 0 /s to 210 0 /s using a Kin-Com dynamometer. Theyonly assessed extension efforts for peak torque.The reproducibility of isokinetic evaluation in a patient group has been rarely tested.Although there are some test-retest studies on healthy subjects, it is erroneous toassume that a similar protocol will prevail for a patient population 229 . If a CKC testingdevice is to be accepted as part of assessment and rehabilitation then thereproducibility of findings derived from its application has to be fully established in anormal population and then applied to populations with relevant pathology.The objectives of this study were (i) to establish a reproducible protocol for combinedhip and knee movement in normal subjects using the Biodex CKC attachment forresultant torque, total work and average power; (ii) if a reproducible protocol wasestablished, to apply it to a patient group with PFPS. Reliability studies often usehealthy subject groups, which although useful, have limited relevance andgeneralisability to patient populations. We wanted to gain comprehensivereproducibility data on multi-joint assessment in healthy subjects, and also show that98

____________________________________________________________Chapter 4CKC testing could be used safely and reliably in patients with patellofemoral painsyndrome.4.2 Methods4.2.1 SubjectsThe right lower limb was assessed in a convenience sample of twenty healthysubjects who volunteered for the study (8 female, 12 male; mean age 30.6 years(±SD,5.5); body mass index (BMI) 23.8(±SD, 0.8). None had a history of lower limbinjury. The patient group consisted of 16 subjects (12 female, 4 male; mean age 29.6years (±SD,5.9); BMI 26.4(±SD, 4.4) with PFPS. This patient group is one of severalorthopaedic dysfunctions in which isokinetic testing, rehabilitation and follow-up areindicated 229 . Patients were included if they had atraumatic unilateral peripatellar painfor greater than six months and not longer than three years. Patellofemoral pain wasreported by the patient as being present during one of the following alone or incombination: prolonged sitting, deep squatting, kneeling, ascending or descendingstairs. Patients were also included if they had a normal radiograph, magneticresonance imaging or arthroscopy, but were excluded if they had other forms ofrecent knee surgery. Patients had further clinical examination to assess theirsuitability and to determine the presence of other lower extremity dysfunction thatmay account for the knee symptoms. These included referred pain from the lumbarspine and hip joint, severe leg length discrepancy, knee ligament, quadriceps tendon99

____________________________________________________________Chapter 4and meniscal pathologies, Hoffa’s syndrome, medial plica syndrome, femoralanteversion and tibial torsion. Examination was also performed to detect loss offlexibility compared to the pain free contralateral limb of the soft tissue structures suchas the quadriceps, hamstrings, triceps surae and iliotibial band which have beenassociated with PFPS 230 . If there were any discrepancies between the affected andunaffected side, then the patients were not entered in the study and were given astretching exercise programme.4.2.2 InstrumentationA Biodex System 2 isokinetic dynamometer (Biodex Medical Systems, Shirley, NY,USA) was used for all tests. The attachment for multi-joint testing was the standarddevice supplied by the manufacturers. All post test data acquisition was performedusing the Biodex Advantage Software (v4.5). On each testing day the machine wascalibrated in accordance with the manufacturer's instructions. The Biodex softwarecompensated for the effects of gravity as part of the setup procedure when thesubject was positioned on the chair (Figure 7).100

____________________________________________________________Chapter 44.2.4 Isokinetic testingSubjects were seated in the chair with the seat angle adjusted to give a maximum of90 0 hip flexion. The position of the seat and other components of the dynamometerwere standardised for each test. Straps were placed over the shoulders and acrossthe waist to ensure the torso was stable. The foot was placed flat against the footplate attachment and was supported by Velcro straps. With the knee at full extensionthe knee joint axis was aligned with the axis of the power head. Ranges of movementlimits were set from 0 0 (full knee extension) to 90 0 of knee flexion with a decelerationcushion setting at 0 (‘hard’) and lever oscillation sensitivity on medium setting ( ‘c’ ).The angular velocity was set at 90 0 /sec (1.57 rad/s). Subjects were asked to placetheir arms across their chest when testing and received the strictly standardisedverbal instructions of “push” and “pull” during the appropriate phase of the movement.Each subject had a practice of 6 submaximal repetitions followed by 2 minutes rest aspart of the warm up prior to the test. The subjects were allowed to see the screenduring the practice session but not during data collection. After 6 maximal repetitionsfor data collection, the subjects had 5 minutes rest before the next test in order toavoid fatigue 231 .4.2.5 Maximum Voluntary Isometric Contraction testingTo test isometric extension, subjects were positioned in the chair as for the isokinetictest, with hip flexion fixed at 90 0 and the knee angle set at 45 0 flexion. The knee anglewas within the range that had been determined in other studies as the most102

____________________________________________________________Chapter 4appropriate to reduce patellofemoral stress to a minimum during testing 50;217 . Toensure that the subjects maintained the 45 0 angle, the operator placed an arm underthe knee to act as a popliteal pad. Subjects pushed into the foot plate without pushingthe popliteal surface of the knee into the operator's arm and beyond 45 0 . Subjectshad practice contractions prior to data collection to familiarise themselves with thismethod and to ensure that they were able to maintain a knee angle of 45 0 . A twitchinterpolation technique was used to ensure a maximum voluntary quadricepscontraction 140;141 . The protocol of subjects performing three maximum contractions of10 seconds duration with 2 minutes rest between each contraction was based on thatof previous researchers in this field 231;232 .4.3 Data AnalysisData were collected for the maximum single torque value (peak torque), total workand average power for extension and flexion during the isokinetic tests. The peaktorque for extension was recorded for the maximum voluntary isometric contraction(MVIC) tests. Statistical analysis was performed using SPSS (Statistical Package forthe Social Sciences) for Windows (V7.5). Assessment of test-retest reliability wasmade by intraclass correlation coefficient (ICC 2,1 ) for single rating for isokinetic peaktorque and mean of ratings for total work, average power and isometric peak torque.as well as the Standard Error of Measurement (SEM). In addition, the mean valuesfor isokinetic extension peak torque and extension MVIC for both groups wereanalysed by independent sample ‘t’ tests to ascertain differences between a patient103

____________________________________________________________Chapter 4and healthy group. Peak torque values were chosen as they are popular isokineticparameters amongst clinicians and researchers 228 . High ICC values do notnecessarily mean that the sets of data agree but rather that there is an associationbetween them 233 . Therefore, Bland and Altman plots for 95% limits of agreementwere also presented. These are visual interpretations of the amount of agreement ofthe means of two trials against the difference between the trials 233 . The use of 95%confidence intervals of the range of differences between the two trials candemonstrate how closely the measurements agree on different occasions. The levelof significance for all calculations was set at the 5% confidence level.4.4 ResultsPrior to analysis, the data were tested using the Kolmogorov-Smirnov test and foundto be normally distributed (p

____________________________________________________________Chapter 4testing (p

____________________________________________________________Chapter 4Table 6. Means±SD, 95% CI’s for all CKC measures. Healthy and PFPS groups106

____________________________________________________________Chapter 4this would indicate no difference between the two trial means. For example, Figure 8shows a comparison between trial 2 and 3 for MVIC in healthy subjects. The meandifference for this test was 1.88Nm (95% CI 4.9 – 8.5) with 95% lower limit ofagreement of -26.88Nm (95% CI -38.5 - -15.2) and 95% upper limit of agreement of30.64Nm (95% CI 19- -42.3). This indicates a high level of agreement between thetwo measures.108

____________________________________________________________Chapter 4Table8 Mean differences, 95% limits of agreements and 95% CI’s for QuadricepsStrengthHEALTHYTest Mean difference (Nm) 95% CIMVIC trials 2 & 3 1.8 ± 14.4 4.9 - 8.5CKC extension trials 2&3 1.3 ± 16.37 -6.56 – 9.16CKC flexion trial 2 & 3 1.69 ± 4.23 0.73 – 3.7195% lower limits of agreementMVIC trials 2 & 3 -26.88 -38.5 - -15.2CKC extension trials 2&3 -30.78 -44.39 - -17.17CKC flexion trial 2 & 3 -6.6 -10.1 - -3.195% upper limits of agreementMVIC trials 2 & 3 30.64 19.0 – 42.3CKC extension trials 2&3 33.38 19.77 – 46.98CKC flexion trial 2 & 3 9.98 13.5 – 6.5PFPS PATIENTSTest Mean difference (Nm) 95% CIMVIC trials 2 & 3 3.3 ± 11.8 -2.88 – 9.48CKC extension trials 2&3 3.5 ± 18.1 -6.1 – 13.1CKC flexion trial 2 & 3 -0.2 ± 3.5 -1.9 – 1.595% lower limits of agreementMVIC trials 2 & 3 -19.8 30.6 – -8.9CKC extension trials 2&3 -31.9 -48.5 - -15.3CKC flexion trial 2 & 3 -7.1 -10.6 - -3.695% upper limits of agreementMVIC trials 2 & 3 26.4 37.26 – 15.54CKC extension trials 2&3 38.9 55.5 – 22.3CKC flexion trial 2 & 3 6.6 10.1 – 3.1109

____________________________________________________________Chapter 46050difference between MVIC 2 &3403020100-10-20-30-40-50-60406080100120140mean of MVIC 2 and 3 (Nm)Figure 8. Bland & Altman plot, MVIC trials 2 & 3, healthy subjects. Means ± 2SD60difference between CKC extension 2 & 350403020100-10-20-30-40-50-606080100120140160180mean of CKC extension 2 & 3 (Nm)Figure 9. Bland & Altman plot for CKC extension trials 2 & 3. Means ± 2SD20difference between CKC flexion 2 & 31612840-4-8-12-16-2020304050mean of CKC flexion 2 & 3Figure 10. Bland & Altman plot for CKC flexion trials 2 & 3. Means ± 2SD110

____________________________________________________________Chapter 45545difference between MVIC 2 &33525155-5-15-25-35-45-55020406080100120140mean of MVIC 2 & 3 (Nm)Figure 11. Bland & Altman plot, MVIC trials 2 & 3, PFPS patients. Means ± 2SD90difference between CKC extension 2 & 370503010-10-30-50-70-90406080100120140160mean CKC extension 2 & 3 (Nm)Figure 12. Bland & Altman plot for CKC extension trials 2 & 3. Means ± 2SD1513difference between CKC flexion 2 & 31197531-1-3-5-7-9-11-13-152030405060mean CKC flexion 2 & 3 (Nm)Figure 13. Bland & Altman plot for CKC flexion trials 2 & 3. Means ± 2SD111

____________________________________________________________Chapter 44.5 DiscussionThis study has established a highly reliable test-retest protocol for the CKCattachment of the Biodex system 2 for a group of healthy subjects. Previous CKCstudies have limited their data to extension parameters. This is possibly the onlystudy to evaluate comprehensively a CKC protocol on not only a group of healthysubjects but also a patient group with a specific knee condition. In this respect, thisstudy has also established similarly high reliability indicating that CKC testing is auseful method of assessing patients with PFPS. This is an important considerationbecause the alternative assessment method using OKC isolated knee extension hasbeen shown to increase patellofemoral stress 221 , and increase strain in the anteriorand posterior cruciate ligaments 217 . An angular velocity of 90 0 /s was chosen followingthe recommendations of Dvir 229that a reasonable and comfortable test velocitybetween 60 0 /s and 180 0 /s would meet the essential requirement of test validity. Sincethen this angular velocity has been used in studies on patients with PFPSsymptomology 234;235 . The ICC of 0.76 for isokinetic CKC peak torque extensionshowed lower test-retest results to the only other study performed on the Biodex CKCattachment 226 . One reason for this difference may be that Lafree et al. performed theirintersession reliability data on only 5 subjects. ICCs for CKC hip and knee flexionhave not been reported before on healthy subjects and our finding of an ICC estimateof 0.75 was highly significant (p

____________________________________________________________Chapter 4Com dynamometer makes extrapolation to other CKC devices difficult becauseprevious authors have cautioned against inter-machine comparisons 236 .This study also highlights the importance of a practice session fully replicating theproper data collection sessions. Johnson & Siegel 237 , using a Cybex II also had threeseparate testing sessions and found stable data after three OKC isokineticcontractions on session one. Kues et al 238 found their subjects’ measurements for KinCom OKC testing became stable during session 2, but concluded that greatest torquevalues were achieved on session 3. Therefore, they recommended that subjectsneeded 2 practice sessions prior to proper data collection. The discrepancy betweenKues et al’s recommendations and this study may be explained by their morecomplex experimental protocol involving a variety of angular velocities and kneeflexion angles. The results from the present study indicate that if a practice session(session 1) was excluded, the ICC estimates for isokinetic peak torque in healthysubjects improve from 0.55 to 0.76 for extension and 0.64 to 0.75 for flexion. TheSEM was also less after a practice session in all parameters except extension (Table7). Interestingly, in healthy subjects MVIC peak torque ICC estimates at 45 0 did notalter with a practice session. This may have been because isometric testing forextension does not require the same degree of complex, co-ordinated musclerecruitment as isokinetic testing for extension and flexion and also a twitchinterpolation technique was used ensuring a maximum contraction. In the PFPSgroup, a similar pattern of results was found in terms of high test re-test reliabilitywhich improved further if the practice session was excluded. The only exception to113

____________________________________________________________Chapter 4this was extension total work, which although still significant (p

____________________________________________________________Chapter 44.6 ConclusionThis study concludes that isokinetic concentric and MVIC values for peak torque,average power and total work using the CKC attachment for the Biodex system 2dynamometer are highly reliable in a group of healthy subjects and patients withPFPS. Researchers and clinicians using the CKC device should have confidence intheir results when testing healthy subjects and patients with PFPS.115

____________________________________________________________Chapter 5Chapter 5MEASUREMENT OFMUSCLE FATIGUE116

____________________________________________________________Chapter 55 MEASUREMENT OF MUSCLE FATIGUE5.1 IntroductionWhen EMS is applied to skeletal muscle there will be effects on the strength orfatigue characteristics of that muscle dependent on the frequency parameters used.The possibility exists that some EMS studies have used an endurance enhancingfrequency but have only measured strength 242 . As a result it may been concludederroneously that EMS is of no benefit in the rehabilitation of the quadriceps. It isimportant therefore to include measures for quadriceps fatigue so that all aspects ofquadriceps function can be assessed. Fatigue can be defined as the failure of amuscle or muscle group to maintain a required or expected force 243and currentclinical techniques for measuring muscle fatigue are problematic. They usuallyproduce an index of muscle fatigue by contracting muscle at a particular force until itcannot be maintained (the failure point) or over a number of repetitions 191 . In additionto the conceptual problem of whether it actually measures fatigue, there are alsosome practical disadvantages of this technique. Firstly, failure is recorded after itoccurs. Secondly, it is a global measure of muscle function because individualmuscles cannot be analysed. Thirdly, microscopic physiological and biochemicalprocesses that can alter the generating force during a submaximal contraction cannotbe detected. Fourthly, there are psychological and emotional factors working duringthe failure point technique that may have more bearing on the results thanphysiological factors 191 . The problems associated with the failure point technique117

____________________________________________________________Chapter 5were confirmed in pre-pilot feasibility work and were deemed unable to fulfill the basicrequirements of validity and reliability. At the same time, other authors suggested thatthe time – scoring of fatigue did not represent an appropriate parameter 244 . Thisoutcome measure therefore needed a technique that could overcome theseproblems.An alternative technique was to employ surface electromyography (EMG). SurfaceEMG is central to a wide range of applications as it enables the electrical behaviour ofthe muscle to be measured in a non-invasive way. It was Piper 245 who first describedthat during a sustained contraction, the EMG signal undergoes frequencycompression. Other workers have noted that the measurement of these changes is amore objective measure of skeletal muscle fatigue 246 . More recently, it has beenproposed that the dominant underlying mechanism for these changes is said to be adecrease in muscle fibre conduction velocity 247 , probably due to a decrease inintramuscular pH and a change in synchronisation and firing rate of muscle fibres 248 .In practical terms there are also several advantages of surface EMG. For example,individual muscles can be monitored simultaneously and fatigue can be analysedduring the initial phase of a contraction, thus negating the use of the failure point.Furthermore, the use of EMG enables data to be collected over a fixed time point(usually 60 s) rather than the open ended, non-fixed-time-point scenario associatedwith failure point techniques.118

____________________________________________________________Chapter 5after fatiguesignal powerbefore fatigueMfa Mfbfrequency (Hz)Mfa = median frequency after fatigueMfb = median frequency before fatigueArea under the curve = the total power of the spectrumFigure 14 Graph showing compression of power spectrumto lower frequencies during a sustained contraction119

____________________________________________________________Chapter 5median frequencyintercept = initial median frequencyslope = fatigue ratetime (60 sec)Figure 15 Representation of intercept and linear regression slope.The EMG signal can be analysed in several ways, but two common measures of thepower density spectrum are the mean power frequency and the median frequency(MF). In theory, both variables are sensitive to a shift to lower frequencies during asustained muscle contraction. The MF is often chosen over mean frequency becauseit is less sensitive to noise 249and more sensitive to spectral compression 250 . Inaddition, MF is recognised as the most widely used measure of spectral shift resultingfrom fatigue 251 . The spectral shift can provide an index of muscle fatigue 246 (Figure 14) that can then be plotted as a linear regression slope to indicate fatigue rate(Figure 15). As a result, clinical applications of this technique have been suggestedas a diagnostic and prognostic aid in musculoskeletal and neuromuscular disorders 248and have been used to distinguish between patients and normal subjects 244 ,and to120

____________________________________________________________Chapter 5evaluate patients undergoing spinal rehabilitation 246 . Reliability has been studied inhuman lumbar 252 , and cervical 253 paraspinal muscles and the upper limb 254 . Thereare, however, very few studies that have examined the reliability of EMG powerspectral analysis of the superficial muscles of the quadriceps group. Recently,Kollmitzer et al. 255 examined the short and long-term reliability of RF, VL, and VMmuscles in 18 healthy subjects. The root mean squared (RMS) and MF wereestimated for 100% MVC and 50% sustained maximum voluntary contraction (MVC)tasks with the knee at 45 0 of flexion. MF reliability was found to be excellent for RF(ICC = .87), whereas the reliability of the VM (ICC = .47), and VL (ICC = .34) werepoor. However, this study assessed the quadriceps in isolated open kinetic chain(OKC) knee extension. OKC assessment using isolated knee extension is the mostcommonly used method to assess function of the quadriceps and the knee, eventhough isolated OKC knee testing may be undesirable or even contraindicated whenassessing patients with pathological conditions of the knee joint 216 . For example,patellofemoral pain syndrome is one of several orthopaedic dysfunctions in whichisokinetic testing, rehabilitation and follow-up are indicated 229 . CKC testing has beenadvocated in favour of OKC testing in this patient group due to the reduction ofpatellofemoral stresses 222 . The improvement in perceived function in patellofemoralpain is thought to be due to the co-contraction of the biarticular muscles of the lowerlimb, proprioception, joint position sense and kinaesthesia 224 . It has been proposedthat the integration of all joints and segments in a movement such as CKC knee121

____________________________________________________________Chapter 5extension is more preferable than an isolated motion of a OKC activity such as seatedknee extension 86 .Although there have been reliability studies of amplitude and frequency parametersfor the quadriceps in OKC knee extension, these results cannot be extrapolated to thequadriceps during CKC evaluation. As the reliability of EMG power spectral analysisfor MF has not yet been investigated on the quadriceps in CKC testing, the aims ofthis study were firstly to investigate the between day reliability of this technique. Ifreliability was established then the second aim was to study the values in a patientpopulation with patellofemoral pain syndrome.5.2 Methods5.2.1 SubjectsA convenience sample of 20 healthy volunteers (10 males and 10 females. Age: 29.3± 5.5 years; BMI: 23.3 ± 3.5) with no lower limb pathology was recruited from theUniversity and hospital community. The patient group consisted of 19 subjects (13female, 6 male. Age 34.2 ± 8.7 years; BMI: 28.0 ± 6.9) with PFPS. Patients wereincluded if they had atraumatic, peripatellar pain for greater than six months and notlonger than three years. Patellofemoral pain was reported by the patient as beingpresent during one of the following alone or in combination: prolonged sitting, deepsquatting, kneeling, ascending or descending stairs. Patients were also included ifthey had a normal radiograph, magnetic resonance imaging or arthroscopy, but wereexcluded if they had other forms of recent knee surgery. All subjects gave their122

____________________________________________________________Chapter 5written, informed consent. The study protocol was approved by the local ethicalcommittee of Manchester School of Physiotherapy and the local ethics researchcommittee of Central Manchester Health Care Trust.5.2.2 Force measurementEach subject was tested on 3 separate days with no less than 24 hours and no morethan 72 hours between consecutive test sessions. Factors such as diurnal variation,temperature, humidity, and menstruation were taken into consideration when planningdata collection. The ambient temperature was monitored for all tests and remainedconstant at 20 0 C 256 .All subjects were instructed in stretching exercises for quadriceps and hamstringmuscle groups and then sat on a Biodex dynamometer (Biodex system Inc. Shirley,N.Y. USA) that was calibrated on each testing day in accordance with themanufacturer’s instructions. An attachment for CKC testing was supplied by themanufacturer to measure the extension torque of the lower limb. Hip flexion was fixedat 90 0 and the knee angle set at 45 0 flexion. The knee angle was previouslydetermined as the most appropriate to reduce patellofemoral stress to a minimumduring testing 50;222 . Practice contractions were performed prior to data collection tofamiliarise the subjects with this method and to ensure that they were able to maintaina knee angle of 45 0 . A twitch interpolation technique was used to ensure a maximumvoluntary quadriceps contraction 140;141 . Subjects performed three maximum123

____________________________________________________________Chapter 5contractions with 2 minutes rest between each contraction 231;232 ; data were collectedfor the maximum single torque value (peak torque). Fifteen minutes rest was allowedbefore the EMG fatigue protocol started 257 .5.2.3 EMG measurementsThe areas chosen for electrode placement were prepared by shaving, if appropriate,abraded by fine sandpaper and cleansed with isopropyl alcohol 258 . Skin (source)impedance was monitored by an impedometer (RS components, UK) with every effortmade to keep the skin impedance between each recording electrode and thereference electrode less than 10 kΩ 259 . If necessary, the site was re-prepared.Electrode positions were determined by using a protractor and tape measure andwere marked with indelible ink. The muscles were determined as follows: VMO at 50 0from the long axis of the femur and 5 cm from the superior medial border of thepatella 79 . The VL at 12 0 -15 0 from the long axis of the femur and 15 cm from thesuperior lateral border of the patella. The RF at 7-10 0 medially in the frontal plane atthe mid-point of the muscle belly, halfway between the anterior superior iliac spineand the superior pole of the patella 260 . A template of all reference points was madewith an acetate sheet for each subject to ensure that the identified landmarks andplacement sites were reproducible (Figure 16) Pairs of pre-gelled silver/ silverchloride surface electrodes (Niko Medical Products, Gloucestershire, U.K.) wereplaced in a bipolar configuration on the skin with the knee in 45 0 of flexion, parallel tothe alignment of the muscle fibres 261with an inter-electrode distance of 5 cm.124

____________________________________________________________Chapter 5Reference (ground) electrodes were placed locally on muscles unrelated to thosebeing investigated 262 .The electrodes were connected to a TEL 100M four-channel remoteamplifier/transmitter system with filtering, offset and gain controls for each channel(Biopac Systems Inc. California USA) (Figure 17). This was connected via a cable toa TEL 100D receiver module, which was in turn connected to the MP 100-acquisitionunit. EMG signals were high pass (8Hz) and low pass (500Hz) filtered (Butterworthfilter), with a sharp notch (band stop) filter of 50Hz. The amplifier was set with a gainof 10, a Common Mode Rejection Ratio (CMMR) of 110-dB minimum and a signal-tonoiseratio of 65dB minimum. There was a differential input impedance of 2MΩ. Thesignal was analogue to digital converted at a sampling rate of 1024 Hz.Figure 16. Use of acetate(left) allowed accurate repositioning of skin marks(right)125

____________________________________________________________Chapter 5VMOV.Lat.R.Fem.Figure 17. EMG electrodes connected to the Biopac Tel 100.126

____________________________________________________________Chapter 55.2.4 EMG Data CollectionSubjects were asked to perform a 60-second isometric contraction at a level of 60%of their MVIC. A submaximal level of 60% was chosen as it was deemed areasonable amount to both obtain some measure of fatigue and be comfortableenough for the patient. The submaximal tasks have been found easier to perform,more stable, and more reliable than maximal tasks 263 . The 60% contraction level wasshown to subjects via a computer-generated line on the dynamometer screen. Datacollection did not commence until the 60% level was reached and ceased before thesubject stopped contracting. Other than completion of the 60s, the test was alsoterminated under two circumstances. If the output appeared to have declined,consistently, to less than 90% of the target force or if repeated artifacts appearedduring the first 25 seconds, indicating possible loss of electrode contact.5.3 Data analysisOn line real time analysis of the EMG signal from each muscle was performed everysecond by a graphical programming analysis system (LabVIEW TM5.0, NationalInstruments, Texas, USA), in order to continuously derive the MF of the power densityspectrum every second, using a Fast Fourier Transform (FFT) algorithm. The medianfrequency (MF) was then computed. The data was exported to Microsoft Excel (97)for off line analysis (Figure 18) and the raw signal checked for artifacts or signalanomalies. A normalisation procedure was required for between subject comparisonin view of the individual anthropometric differences and, despite painstaking efforts,127

____________________________________________________________Chapter 5any variations in standardising electrode placement 260 . MF was, therefore, normalisedagainst initial median frequency (IMF) during the static MVIC, which is by far the mostcommonly used normalisation method 264 . A slope of regression was derived toindicate MF decline. This slope was used to describe the rate of change over thecontraction time to express a fatigue rate.Hz140120100806040200VL = -0.0566time (0-60 s)Figure 18 A typical normalised graph of data from Vastus Lateralis (VL)rate of fatigue. The linear regression line is fitted (in black) and the equation is in %/s5.3.1 StatisticsAssessment of test-retest reliability was made by intraclass correlation coefficient(ICC 1,3) for single rating 265 . The reason for selecting this ICC equation was to test intrarater reliability of the fatigue measure repeated over three tests. The first integerrepresents the number of raters and the second integer the number of measures 266 .128

____________________________________________________________Chapter 5This equation is also appropriate when the reliability of a specific protocol is beingtested as a precursor to a main trial (as is the case here) rather than to provideinformation of generalisability. Statistical analyses were performed using SPSS(Statistical Package for the Social Sciences) for windows (v.9) to determine theintraclass correlation correlation (ICC).A repeated measures ANOVA was used to test for significance interactions betweentime and gender for all muscles for IMF and MF. ‘Excellent reliability’ described ICCvalues in the range 80 – 100% and ‘good reliability’ described ICC values in the range60 – 80%, whereas values below 60% indicated ‘poor reliability’ 267 . Statisticalsignificance was accepted at the 5% confidence level.As discussed in Chapter 4, ICCs alone do not represent a complete analysis ofreliablity, therefore Bland and Altman plots with 95% limits of agreement between thetrials were also calculated 233 . Outliers, bias or relationships between variance inmeasures can therefore be easily observed 268 .5.4 ResultsPrior to analysis the data were tested using the Kolmogorov-Smirnov test and foundto be normally distributed (p>0.05), thus indicating analysis by parametric statistics.There were no statistically significant interactions for time and gender for all musclesand IMF and MF (p>0.05). Therefore the data for the male and female subjects werepooled and reported as a single sample.129

____________________________________________________________Chapter 55.4.1 Torque measurementsAs expected, there were lower torque values in the PFPS group than the healthy.This finding concurs with the previous chapter and work since published in differentgroups of healthy and PFPS patients using the CKC attachment 269 . Reliability of theMVIC torque measurements was excellent (ICC = .91 in healthy subjects; ICC = .82in PFPS subjects). The reliability improved when the training session was excluded(ICC = .96 in healthy; ICC .92 in PFPS).5.4.2 EMG measurements5.4.2.1 Initial Median FrequencyTable 9 shows group means ±SD, SEM, and ICCs for the IMF for all muscles with andwithout the practice trial. The healthy group showed excellent reliability between trials2 and 3 for VL (ICC 1.3 .81) and RF (ICC 1,3 .82), with good between-days reliability forVMO (ICC 1,378). In the PFPS group, similar reliability between trials 2 and 3 wasdemonstrated on VMO (ICC 1,3 .68), on VL (ICC 1,3 .86) and RF (ICC 1,3 .69).5.4.2.2 Median FrequencyTable 9 also shows the group means ±SD, SEM, and ICCs for MF for all muscles withand without the practice trial. In the healthy group, good between-days reliability wasdemonstrated in the MF slope of the VL and VMO with ICC 1,3 .74 and .72respectively. In contrast, there was poor reliability for the MF slope of RF with an130

____________________________________________________________Chapter 5ICC 1,3 of .33. There was a similar pattern in the PFPS group, with reliability betweentrials 2 and 3 being excellent for RF(.81), good for VMO (.62), and poor for VL (.39).Table10 shows the means ±SD and 95% CI for MF for each trial separately. In thehealthy group, there was a decline in the mean values for all muscles during the threedifferent trials, with MF slope declines of the mono-articular muscles being larger thanthe bi-articular muscle (VMO -0.14; VL -0.12; RF -0.06). Bland & Altman plots werealso calculated for the limits of agreement between trials 2 and 3. The limits ofagreement were defined as the mean difference of the two trials plus and minus twostandard deviations (± 2SD). Thus if all the markers were on the zero line this wouldindicate no difference between the two trial means. Table11 shows the values for95% limits of agreement and 95% confidence intervals. Figures 19, 20, and 21 showplots for each of the muscles of healthy subjects; figures 22,23,24 show those for thePFPS patients. This shows that the majority of values are well within the 95% limits ofagreement. For example, the mean difference in Figure 19 is -0.019 %/s (95% CI -0.23 - -0.061) with 95% lower limit of agreement of –0.219 (95% CI -0.3 - -0.14) and95% upper limit of 0.196 (95% CI 0.11 – 0.28).131

____________________________________________________________Chapter 5Table 9 Group Means ±SD, ICC, and SEM for the IMF and MFfor all muscles and all trials. Normalised data.HealthyPFPSIMF Mean ±SD SEM SDD ICC 1,3 Mean ±SD SEM SDD ICC 1,3VMO 1,2 64.41 (9.93) 7.27 31 .55 63.66 (6.91) 2.97 13 .60VMO 2,3 63.24 (8.70) 2.85 12 .78 65.42 (6.99) 7.37 32 .68VL 1,2 61.26 (7.17) 7.26 31 .65 65.25 (7.13) 7.72 35 .36VL 2,3 61.41 (7.94) 2.00 9 .81 64.12 (9.01) 1.68 8 .86RF 1,2 60.72 (9.72) 2.60 12 .80 60.71 (8.43) 1.08 5 .30RF 2,3 59.74 (9.69) 2.52 12 .82 61.22 (8.13) 3.08 14 .69MFVMO 1,2 -0.123 (0.127) 0.144 41 .33 -0.098 (0.066) 0.054 123 .37VMO 2,3 -0.140 (0.127) 0.055 117 .72 -0.118 (0.089) 0.066 131 .62VL 1,2 -0.118 (0.057) 0.207 775 .34 -0.074 (0.071) 0.069 162 .15VL 2,3 -0.120 (0.117) 0.045 130 .74 -0.096 (0.065) 0.111 256 .39RF 1,2 -0.071 (0.061) 0.283 990 -.59 -0.055 (0.088) 0.027 105 .09RF 2,3 0.062 (0.106) 0.120 369 .33 -0.091 (0.082) 0.151 598 .81Legend: IMF = Initial Median FrequencyMF = Median FrequencySEM = Standard Error of MeasureICC = Intraclass Correlation CoefficientVMO = Vastus Medialis ObliqueVL = Vastus LateralisRF = Rectus Femoris132

____________________________________________________________Chapter 5Table10 Means±SD & 95% CI’s for EMG MF slopes. Healthy and PFPS groupsHealthyPFPSMEAN ±SD 95% CI MEAN ±SD 95% CIVMO 1 -0.099 0.169 -0.178 ~ -0.019 -0.082 0.069 -0.116 ~ -0.047VMO 2 -0.146 0.139 -0.211~ -0.080 -0.119 0.091 -0.165 ~ -0.074VMO 3 -0.134 0.136 -0.198~ -0.070 -0.121 0.112 -0.176 ~ -0.065VL 1 -0.087 0.071 -0.120 ~ -0.053 -0.053 0.107 -0.106 ~ -0.0008VL 2 -0.149 0.127 -0.209 ~ -0.090 -0.103 0.078 -0.142 ~ -0.065VL 3 -0.092 0.122 -0.149 ~ -0.034 -0.096 0.078 -0.134 ~ -0.056RF 1 -0.070 0.113 -0.123 ~ -0.016 -0.014 0.036 -0.090 ~ 0.062RF 2 -0.072 0.141 -0.138 ~ -0.006 -0.095 0.089 -0.139 ~ -0.051RF 3 -0.059 0.111 -0.113 ~ -0.006 -0.089 0.086 -0.132 ~ -0.046Legend:VMO = Vastus Medialis ObliqueVL = Vastus LateralisRF = Rectus femorisPFPS = Patellofemoral pain syndrome patients133

____________________________________________________________Chapter 5Table11 Mean differences, 95% limits of agreements and 95% CIs for QuadricepsEnduranceHEALTHYTest Mean difference (%/s) 95% CIVMO trials 2 & 3 -0.019 ± 0.104 -0.023 - -0.061VL trials 2 & 3 -0.058 ± 0.089 -0.10 – 0.02RF trials 2 & 3 -0.217 ± 0.146 -0.08 - -0.0495% lower limits of agreementVMO trials 2 & 3 -0.219 -0.30 - -0.14VL trials 2 & 3 -0.23 -0.29 - -0.17RF trials 2 & 3 -0.31 -0.44 - -0.1895% upper limits of agreementVMO trials 2 & 3 0.196 0.11 – 0.28VL trials 2 & 3 0.12 0.06 – 0.18RF trials 2 & 3 0.26 0.13 – 0.39PFPS PATIENTSTest Mean difference (%/s) 95% CIVMO trials 2 & 3 0.002 ± 0.0088 -0.04 – 0.04VL trials 2 & 3 -0.001 ± 0.0087 -0.04 – 0.04RF trials 2 & 3 -0.001 ± 0.0058 -0.03 – 0.0395% lower limits of agreementVMO trials 2 & 3 -0.17 -0.23 - -0.11VL trials 2 & 3 -0.17 -0.23 – 0.11RF trials 2 & 3 -0.11 -0.16 - -0.0695% upper limits of agreementVMO trials 2 & 3 0.17 0.11 – 0.23VL trials 2 & 3 0.17 0.23 – 0.11RF trials 2 & 3 0.11 0.06 – 0.16134

____________________________________________________________Chapter 5.5.4difference between VMO 2 & 3.3.2.1.0-.1-.2-.3-.4-.5-.6-.5-.4-.3-.2-.10.0.1mean VMO 2 & 3 (slope %/s)Figure 19.Bland & Altman Plot, trials 2 & 3 for VMO,healthy subjects.Means ±2SD.5.4difference between VL 2 & 3.3.2.1.0-.1-.2-.3-.4-.5-.6-.5-.4-.3-.2-.10.0.1mean of VL 2 & 3 (slope %/s)Figure 20. Bland & Altman Plot, trials 2 & 3 for VL, healthy subjects. Means ± 2SD.9difference between RF 2 & 3.6.3.0-.3-.6-.9-.4-.3-.2-.10.0.1.2mean of RF 2 & 3 (slope %/s)Figure 21. Bland & Altman Plot, trials 2 & 3 for RF, healthy subjects. Means ± 2SD135

____________________________________________________________Chapter 5.6.5difference between VMO 2 & 3.4.3.2.1-.0-.1-.2-.3-.4-.5-.6-.6-.5-.4-.3-.2-.10.0.1mean of VMO 2 & 3 (slope %/s)Figure 22. Bland & Altman Plot, trials 2 & 3 for VMO, PFPS patients. Means ±2SD.5.4difference between VL 2 & 3.3.2.1.0-.1-.2-.3-.4-.5-.3-.2-.10.0.1mean of VL 2 & 3 (slope %/s)Figure 23. Bland & Altman Plot, trials 2 & 3 for VL, PFPS patients. Means ± 2SD.5.4difference between RF 2 & 3.3.2.1.0-.1-.2-.3-.4-.5-.4-.3-.2-.10.0.1.2mean of RF 2 & 3 (slope %/s)Figure 24. Bland & Altman Plot, trials 2 & 3 for RF, PFPS patients. Means ± 2SD136

____________________________________________________________Chapter 55.5 DiscussionThe present study has examined the reliability of the IMF and MF slope of the VMO,VL and RF during sustained submaximal CKC isometric contractions. Once areliability protocol was established in a healthy subject group, the technique was thenapplied to a patient group with PFPS. This seems to be the first study to analyse IMFand MF reliability in the quadriceps muscle in CKC lower limb extension rather thanisolated OKC knee extension; a method that represents a more functionalassessment of the lower limb. Although OKC knee extension is a commonly used andreliable procedure for some muscles 255 , this method may be contraindicated whenapplying the technique on various knee pathologies 216 . Previous studies have noted apain inhibitory effect on EMG data during OKC knee extension 241 . As CKC testingseems to hold several advantages over OKC, the present study has attempted toassess its value and reliability when taking EMG data in a patient population.5.5.1.1 Initial median frequencyIn the healthy group, IMF was the most reliable parameter across trials. The VMO, VLand RF exhibited good to excellent reliability of IMF (ICC 1,3 = .78, .81, .82). Thesedata compare with those reported for back muscles during a trunk holding test (ICC 2,1range 0.79 to 0.86 270 . Other studies investigating the reliability on healthy back andcervical paraspinal muscles have revealed better reliability of the IMF than ourstudy 252 . Merletti et al 271 also reported better IMF reliability for the vastus medialis(ICC = .86), but they used electrically evoked rather than voluntary isometric137

____________________________________________________________Chapter 5contractions in the OKC testing position. In the PFPS group there was similarexcellent to good reliability for VMO, VL and RF ( .68, .86, .69).5.5.1.2 Median FrequencyThe current study showed varying reliability of the MF slopes during CKC submaximalisometric contractions. In both the healthy and PFPS groups, ICCs varied betweenthe recording sites and between days. There have been several studies examiningquadriceps MF reliability in the OKC testing mode. Cornwall et al. 272 demonstratedgood within day reliability for the VL only (ICC range .77 to .82). Similar reliability wasreported for VM only (ICC .79) 273 . Merletti and colleagues 271 reported between dayPearson’s correlation coefficient ranging from r =.94 to .95 for the IMF and .59 to .72for the MF slope of VM only. Kollmitzer et al. 255examined the three superficialquadriceps and reported poor between days reliability for the VM (ICC= .47) and VL(ICC= .34), but excellent reliability for the RF muscle (ICC = .87). The lack of reliabilityin VM and VL was attributed to subtle rotations resulting in altered loading that mayoccur in the thigh during sustained isolated knee extensions. It is well accepted thatelectrode placement can influence the EMG signal and one of the main causes ofpoor between-days reliability is inaccurate replacement of electrodes 274 . Interestingly,Kollmitzer et al. 255 had high within days reliability without removing the electrodes, butmuch poorer between days reliability six weeks later when they only approximatedelectrode positions. In the present study, great care was taken to standardise theelectrode positions between testing days by marking the skin and using an acetate138

____________________________________________________________Chapter 5template for all reference points to ensure consistent electrode position. VariableICCs of the MF might be further explained by influences such as changes in electrodelocation and muscle length 191 .These results raise two issues in need of further discussion. Firstly in the healthygroup, although VL had a high between trials (2 & 3) reliability (ICC 1,3 .74) furtheranalysis with a repeated measures ANOVA indicated a significant difference betweentrials (p< 0.01) (Table 12).Table 12. A Two-way analysis of variance ANOVA for the MF slopeof the VMO, VL and RF muscles during trials 2 and 3Between –Subjects varianceBetween - Trials variancedf F P df F PVMO 19 6.04 0.0001* 1 0.26 0.6VL 19 6.79 0.00005 * 1 8.39 0.009 *RF 19 2.02 0.06 1 0.23 0.6Legend:VMO = Vastus Medialis ObliqueVL = Vastus LateralisRF = Rectus Femoris* = Significant at P < 0.05139

____________________________________________________________Chapter 5A Scheffé post hoc analysis found a significant difference between trials 2 and 3. Ifthis is the case, then the MF slope cannot be considered a reliable technique in thisparticular muscle. Secondly, in contrast, there was poor reliability of RF (ICC 1,3 .33).However, a repeated measures ANOVA showed no significant difference betweentrials 2 and 3 (p = 0.6). One reason for the RF ICC to be as low as .33 was largerbetween-trials differences at this recording site. Methodological factors, even thoughthese were controlled as strictly as possible, have already been discussed as onereason for the day-to-day variations. Another reason was that the between subjectsvariance was smaller than at other recording sites, as can be seen by the nonsignificant F-value test between-subjects variance (Table 12). Insufficient betweensubject variability to adequately assess within-subject agreement has been notedpreviously on MF fatigue data, albeit on the upper limb 254 . These authors advised theneed for sufficient variability in overall measures to assess reliability. Consequently,caution needs to be exercised when quoting the ICC value from statisticalprogrammes that may be misleading if taken in isolation from other calculations 268 .A further reason for variability of the EMG signal and MF may be the more complexactions of CKC assessment. In OKC testing, knee extension contractions may beattributed solely to knee extensors, whereas in a more functional assessment of thelower limb using CKC tests the knee extensors cannot be isolated due to cocontractionsof additional muscles such as hip and ankle extensors. Yang andWinter 263 proposed that in movements where a number of synergists are involved anda maximal effort is required, (such as a lower limb CKC extension) more variability140

____________________________________________________________Chapter 5would be observed than in simpler movements. Varying contributions andinconsistent synchronisation of the synergists would thus affect between trials andbetween days reliability. This may account for the differences in MF fatigue ratesobserved in the present study during CKC tests and those of other authors usingOKC tests. This is especially so for RF that was more susceptible to fatigue thaneither VM or VL during OKC submaximal isometric contractions 259 but was the leastsusceptible in CKC testing (Table 10). This section has also highlighted theimportance of a practice session that fully replicates the testing protocol. The resultshave shown that ICC values between trials 1 and 2 were always worse for all musclesand both IMF and MF in the healthy group (Table 9). These values vastly improvedwhen values were calculated between trials 2 and 3. This pattern of results alsooccurred in the PFPS group. As far as is possible to ascertain, no research has beenconducted to determine how practice affects the reliability of EMG power spectrumanalysis technique. A full practice session is therefore recommended prior to properdata collection.A final consideration is the usefulness of IMF. Clearly, the reliability of this measurewith good to excellent ICCs and low SEM in both the healthy and PFPS groupsexceeds that of the MF slopes (Table 9). However, there has been renewed debateas to whether the IMF can be used as a physiological parameter of muscle. Initialthoughts were that IMF may be able to determine the fibre composition of muscle 275 .A high IMF would be an indication of more fast fibres in a muscle based on theobservation that during a contraction of fast fibre muscle there is a short action141

____________________________________________________________Chapter 5potential and an increase in the higher frequency components of the spectrum.Observations in the lumbar 276 , or cervical musculature 253of correlations betweenIMFand muscle biopsy fibre typing have not been confirmed in the human quadriceps.With these considerations there was no purpose in gathering and analysing IMF inthe Pilot study in Chapter 8 or the Main study in Chapter 9 other than to complete thenormalisation process for MF.5.6 ConclusionUsing a CKC testing device, this study has shown good to excellent reliability in allmuscles for IMF in both a healthy group and a patient population with PFPS. It hasshown good reliability of MF for VMO and VL in healthy subjects. MF reliability forpatients with PFPS was also good in VMO and excellent in RF but poor in VL.Monitoring the fatigue rate of the VMO and RF rather than the VL would be a moresuitable measure for use in clinical situations. Further research would be needed toestablish reliability in other patient groups. This study has also highlighted the needfor a full practice session fully replicating the proper data collection trials.142

____________________________________________________________Chapter 6Chapter 6MEASUREMENT OFPATELLAR PAIN143

____________________________________________________________Chapter 66 MEASUREMENT OF PATELLAR PAINAlthough objective measures of patients’ strength, function and performance arefacilitated by numerous technical methods, subjective complaints of knee pain ingeneral and PFPS in particular are more difficult to measure. Yet these outcomemeasures are no less important as pain is usually the patient’s main complaint.6.1 Visual Analogue ScaleThe Visual Analogue Scale (VAS) is a popular means of measuring pain in a varietyof clinical contexts. It is quick and easy to administer, easy for the researchers toscore and the patients do not need to be highly motivated to complete it 277 . A VASwas used in this study because it has been found to be reliable and valid in themeasurement of pain intensity 278;279 . Furthermore, the VAS has also been used inknee complaints 280 in which it was more acceptable for patient use than the Noyes orLysholm knee scales, and specifically in PFPS 281;282 .In the present study, patients were asked to allocate the appropriate number on theVAS that corresponded to their patellar pain at that particular moment. It consisted ofa numerical scale of pain intensity ranging from 0 - ‘no pain ‘ to 10 - ‘severe pain’.This was done at the same time point of each assessment, i.e. whilst sitting and priorto any physiological or functional testing in order to prevent ‘contamination’ from otheraspects of the testing procedure 277 . Although the VAS is a useful tool to quantify pain,more in depth multidimensional scoring methods were included to give a betteroverall picture of the patients pain 277 . These are discussed in the next section.144

____________________________________________________________Chapter 66.2 Kujala ScoreThere have been many scales and scoring systems for the knee joint 280 but many arenot specific enough for the symptoms of PFPS. Kujala et al. 283 developed a self-reportquestionnaire scoring system of 13 questions, carefully weighted to give a maximumbest score of 100 points. The system evaluated pain during stair climbing, squatting,running, jumping and prolonged sitting with knees flexed; the presence of a limp,swelling, or subluxation; the amount of quadriceps atrophy and limitation of flexion;the need for support when walking. The authors related them to an objective measureof patellar position analysed by MR scanning. They also compared a group of healthysubjects with groups of patients diagnosed with either PFPS, patellar subluxation, orpatellar dislocation. The questionnaire differentiated clearly between the groups (p

____________________________________________________________Chapter 6good correlation with the VAS in a group of patients with PFPS (n = 19, Pearson’s r =0.72, p

____________________________________________________________Chapter 7Chapter 7MEASUREMENT OFQUADRICEPSCROSS SECTIONAL AREA147

____________________________________________________________Chapter 77 MEASUREMENT OF QUADRICEPS CROSS SECTIONALAREA7.1 IntroductionQuadriceps muscle wasting is a common clinical observation in patients with lowerlimb disease, injury or after immobilisation 287 . One theory is that pain causes reflexinhibition of the quadriceps, which in time induces an atrophic response within themuscle with subsequent loss of muscle size 288 . Most authors state that the loss ofsize is due to a decrease of muscle fibre area (atrophy) rather than a loss of fibrenumbers (hypoplasia) 287 .Usually, estimations of quadriceps wasting in the clinical setting have used girthmeasurements, but this method also involves other posterior, lateral, and medial thighmuscles as well as subcutaneous fat and bone. The test-retest reliability of thismethod has been found to be poor with numerous factors accounting for inter andintra operator variability 289 .More sophisticated techniques are available in the research setting such asultrasound scanning to measure cross sectional area (CSA) which was first describedfor human skeletal muscle in the 1960s and for the quadriceps specifically by Dons etal. 290 . Since then the technique has been developed and superseded by CT scanningand, more recently, magnetic resonance imaging (MR). However, ultrasoundscanning is non invasive, inexpensive and used by physiotherapists independentlywhich makes it still an attractive measurement tool. It has been demonstrated that the148

____________________________________________________________Chapter 7mean differences between ultrasound and MR imaging in estimating quadriceps CSAis only 0.8%, concluding that these limits are small enough for either ultrasound orMR to be used in clinical practice 291 .The pieces of equipment for ultrasound scanning in this thesis have been usedpreviously to study the quadriceps, and both face and criterion validity have beendemonstrated with a mean percentage of coefficient of variation (%CV) of 0.4% 292 .Reliability has also been investigated in both intra-rater reliability of repeatedmeasures (mean %CV = 2.8% for one and 1.9% for two raters) and inter-raterreliability (mean %CV 2.4) 292 . As a different rater was being used for this thesis, it wasdeemed necessary to re-investigate intrarater reliability.The two aims of this section were to establish intrarater reliability between scans anddays and, secondly, the single rater reliability of location of the muscle borders.7.2 MethodUltrasound scans were taken of the right quadriceps of 9 healthy subjects (5 male, 4female; mean age 30.6 ± 5.5 years).The scanning device was a static compound B ultrasound scanner (Technicare EDP1200) (Figure 25). A 5 and 2.25 MHz transducer with focal lengths of 13 and 19mmwere used for lean and obese subjects respectively. Coupling medium was used forall scans (Sonartrack, Diagnostic Sonar Ltd). A thermal printer (Sony Video Graphicprinter, UP 910) provided hard copies of the images (Figure 26) and the area of thequadriceps muscle group was calculated using a planimetry system that consisted of149

____________________________________________________________Chapter 7a graphics tablet (Graphtec Digitizer, KD4030) with 'Digiteye' software (MedicalPhysics Department, Hope Hospital Salford UK).Figure 25. Compound B ultrasound scanningof the mid thigh section of the quadriceps muscle group150

____________________________________________________________Chapter 7Figure 26 Image produced by Compound B scannerFigure 27. A detailed cross section of quadriceps for comparisonwith the ultrasound scan in Figure 26 above.(From Gray’s anatomy: reproduced with permission)151

____________________________________________________________Chapter 7Patients lay supine on a couch. The lower limb was positioned in a neutral position forrotation (i.e. 0 0 medial and 0 0 lateral rotation) by a sandbag and velcro strapsattached to small board. A protractor confirmed neutral rotation. The scan took placeat the mid section of the thigh (Figure 25). This point lay half way from the greatertrochanter to the lateral joint line of the knee and was determined by using a tapemeasure. The mid thigh position was marked on the thigh. To improve accuracy ofrepositioning for the post treatment scan a template of all reference points was madewith an acetate sheet for each subject to ensure that the identified landmarks and thescan thigh mark were reproducible. The CSA was calculated by examining the hardcopy (Figure 26) and tracing around the outer borders of the VM, VL and RF muscleswith the hand held cursor of the planimetry system. The drawing included the vastusintermedius, but care was taken not to include the long head of biceps femoris,adductor longus or sartorius muscles in the tracing. The area of the shape from thetracing was then calculated by the software. Each scan was repeated six times andthere was an interval of seven days between tests.7.3 Statistical analysisStatistical analyses were performed using SPSS (Statistical Package for the SocialSciences) for windows (v.9). Analyses were performed for intrarater reliability for CSAand intrarater reliability for location of muscle borders. The previous method ofassessing reliability of this technique 292 using a coefficient of variation (CV) is now152

____________________________________________________________Chapter 7considered inappropriate for assessing reliability 266 . Therefore reliability wasassessed in four ways:1. Intraclass correlation coefficient (ICC 1,1 ) for between scans reliability and ICC 1,2 forbetween days reliability 265;266 . ICCs were performed on the data from scans on day 1and day 2 and then from the mean of those within days scans for between daysreliability.2. Quoting the ICC value may be misleading if taken in isolation from othercalculations 268 . Therefore the standard error of measure (SEM) was also calculated,which shows the consistency of the measurement with the advantage of being in thesame units.3. A Bland and Altman plot was calculated showing the differences between the CSAmeasures on the 2 days against the mean of the measures on 2 days with ±2SD.4. The smallest detectable difference (SDD) is a parameter applied in recent reliabilitystudies 293 . This presents a clinically applicable percentage figure for the amount ofchange needed to detect a true change in a subject's or rater’s performance.7.4 Results7.4.1 Intrarater reliability1. Within days, between scans reliability was excellent for both days. ICC 1,1 valueswere 0.99 for day 1 and 0.99 for day 2. Between days reliability was also excellentwith an ICC 1,2 of 0.99.153

____________________________________________________________Chapter 72. The SEM for the scans on day 1 was 0.29cm 2 , for day 2 was 0.38cm 2 . Betweendays SEM was 0.29cm 2 .3. The SDD calculated for the between scans on day 1 was 0.81cm 2 or 3.4% and forday 2 was 1.07 cm 2 or 4.5%. The SDD calculated for between days was 0.80 cm 2 or3.3%.4. The limits of agreement for the Bland & Altman plot were defined as the meandifference between the measures ±2SD ( Figure 28). The mean difference was -0.0055cm 2 (95%CI 0.314 - -0.384) with a 95% lower limit of agreement of –0.83(95%CI -0.27 - -1.38) and a 95% upper limit of 0.84 (95%CI 1.39 – 0.29).7.4.2 Location of muscle borderThe intrarater reliability of locating muscle borders was excellent.ICC 1,6 values were 0.99. The SEM was 0.19 cm 2 . The SDD calculated was 0.52 cm 2or 2.2%. In addition, a repeated measures ANOVA showed no significant differencebetween the six values (P= 0.649). All results are summarised in Table 13 below.Table 13 Intrarater reliability of ultrasound scanning techniquefor Quadriceps Cross Sectional AreaICC 1,1 ICC 1,2 95% CI SEM(cm 2 )(cm 2 )SDD(cm 2 )Between scans day 1 0.99 18.78 - 28.28 0.29 0.81 3.4Between scans day 2 0.99 18.85 - 28.29 0.38 1.07 4.5Between days (means) 0.99 18.80 - 28.29 0.29 0.80 3.3Locating muscle border ICC 1,6 0.99 18.83 - 28.54 0.19 0.52 2.2SDD(%)154

____________________________________________________________Chapter 73.0difference between CSA day 1 &22.01.00.0-1.0-2.0-3.014161820222426283032mean of CSA day 1&2 (Cm2)Figure 28. Bland & Altman plot for CSA measures between days. Means ± 2SD7.5 ConclusionIn practical terms these results mean that quadriceps CSA would have to change bymore than 3.3% or by 0.80cm 2 in order to state that a treatment had an effect on thisoutcome measure. This section has indicated via previous studies that the staticcompound B ultrasound scanner has both face and criterion validity 292 , and hasshown excellent intrarater reliability for between scans on both days 1 and 2 and alsobetween days. These results compare favourably with previous studies assessing theintrarater reliability of ultrasound scanning of the quadriceps using static compound Bscanning 292 and of the anterior tibial muscles using a real time scanner 266 .155

____________________________________________________________Chapter 8Chapter 8THE PILOT STUDY156

____________________________________________________________Chapter 88 PILOT STUDY 8v88.1 IntroductionThe next phase of the study was to conduct a Pilot study fully replicating the Mainstudy. This had several advantages. Firstly, all the outcome measures could be usedon a similar patient population as the Main study. Secondly, the results allowedproper calculation of appropriate sample size for the Main study. Thirdly, an important(and often neglected) consideration is that the Pilot study allowed the procedures,mechanics and overall flow of the study to be assessed. It was estimated from thereliability studies that a full patient assessment would take at least 60 minutes.Minimising this as much as possible for patient comfort and co-operation andensuring proper test sequence was considered as important component of this phase.This Pilot study evaluated a new form of electrical muscle stimulation withsimultaneously combined high and low frequency components (RESTIM) andcompared it to a commercially existing form of sequentially combined frequencies(COMPEX). The outcome measures were muscle strength, muscle fatigue, range ofmotion, pain, function, a step test and quadriceps CSA. The research design was adouble blinded randomised trial on patients with PFPS. The null hypothesis was thatthere would be no statistical difference between the two stimulation groups157

____________________________________________________________Chapter 88.2 Methods8.2.1 SubjectsPatients were referred from the orthopaedic clinics in one hospital with a clinicaldiagnosis of patellofemoral pain. Of the 30 patients referred for this study, 7 hadequal quadriceps CSA, 5 had abnormal gait parameters, 1 had referred pain from thehip joint and 1 had referred lumbar spine pain (see sections 8.2.1.2 and 8.2.1.3below). These patients were subsequently excluded, leaving a total of 16 patients toenter the study (mean age = 29.6 ± 5.9 years; BMI = 26.4 ± 4.4). All patients had theprotocol and procedures explained to them, were given an information sheet, andsigned a consent form if they wished to enter the study. The age limits were 18 – 60years. The study was approved by the ethics committee of the Central ManchesterHealthcare Trust.8.2.1.1 Inclusion criteriaPatients were included if they had atraumatic peripatellar pain for greater than sixmonths and not longer than three years. Patellofemoral pain was provoked by one ofthe following alone or in combination: prolonged sitting, deep squatting, kneeling,ascending or descending stairs. Additional inclusions were CSA differences betweenaffected and unaffected limb to be greater than 4%. Patients were also included ifthey had a normal radiograph, normal MR scan or normal arthroscopy, if performed.158

____________________________________________________________Chapter 88.2.1.2 Exclusion criteriaPatients were excluded from the study if they had epilepsy, cancer, a cardiacpacemaker, a suspected heart problem, or if they had recent surgery (not includingarthroscopy). Patients younger than 18 years and older than 60 years were notinvited to participate in the study. In order to exclude abnormal foot and anklepronation as the cause of PFPS the patients were screened by kinetic gait analysisusing a force plate (Kistler Bio-mechanics Ltd. Switzerland.) to detect abnormalvalues of mediolateral force as described by Callaghan & Baltzopoulos 57 .8.2.1.3 Clinical examinationPatients had further clinical examination to assess their suitability and to determinethe presence of other lower extremity dysfunction that may account for the kneesymptoms. These included referred pain from the lumbar spine and hip joint, severeleg length discrepancy, knee ligament, quadriceps tendon and meniscal pathologies;patella tendinitis ('Jumper's knee'); tibial tubercle apophysitis (Osgood Schlattersdisease); bursitis; infrapatella fat pad lesion (Hoffa’s syndrome); medial plicasyndrome; femoral anteversion and tibial torsion, bipartite patella 1and alsoosteochondritis dessicans patella 294 . Examination was also performed, as mentioned inChapter 2.3.2.2., to detect loss of flexibility of the soft tissue structures such as thequadriceps, hamstrings, triceps surae and iliotibial band that have been associatedwith PFPS 230 .159

____________________________________________________________Chapter 88.3 Outcome measures8.3.1 InstrumentationIsometric and isokinetic concentric extension torque of the lower limb was measuredusing the Biodex system 2 isokinetic dynamometer (Biodex systems Inc. Shirley N.Y.USA) with a closed kinetic chain attachment as supplied by the manufacturers. Thisattachment has been assessed for extension test –retest reliability in PFPS patientswith ICC estimates 0.92 for isometric mode and 0.85 for isokinetic mode in Chapter4 269 . The closed kinetic chain method was chosen in preference to the standardisokinetic lever arm as previously described in Chapter 4 because the latter wasthought to exacerbate the patients’ patellofemoral symptoms. Closed kinetic chainexercise has been advocated for patients with PFPS due to a lessening of thepatellofemoral joint reaction force and patellofemoral stress 222 . It was demonstratedthat there were significantly fewer stresses at the patellofemoral joint at the mostfunctional range of movement during a leg press (CKC) exercise than a leg extension(OKC) exercise. A CKC method of assessment may not only bring about objectivechanges, but also lead to improvement in perceived function in patellofemoral painsyndrome 223 .8.3.2 Isometric StrengthSubjects were positioned in the Biodex chair with the hip at 90 0 flexion and the kneeangle at 45 0 flexion. This positioning is an exact replication of the reliability study in160

____________________________________________________________Chapter 8Chapter 4. This angle had been determined in other studies as the most appropriateto reduce patellofemoral stress to a minimum during testing 222 . To ensure that thesubjects maintained the 45 0 angle, the operator placed a hand under the knee to actas a popliteal pad. Subjects pushed into the foot plate without lowering the poplitealsurface of the knee into the operator's hand (and thus beyond 45 0 ). Subjects hadpractice contractions prior to data collection to familiarise themselves with this methodand to ensure that they were able to maintain a knee angle of 45 0 . Twitchinterpolation was used to ensure a maximum voluntary isometric contraction 140;295 .Subjects performed three maximum contractions of 10 seconds duration with 2minutes rest between each effort 232 . The concentric peak extension torque wasrecorded.8.3.3 Isokinetic strengthIn an exact replication of positioning in the reliability study in Chapter 4, subjects wereplaced in the chair with hip flexion set at 90 0and the shoulder and waist strapsapplied. The foot was placed flat against the foot plate attachment and was held inplace by velcro straps. With the knee at full extension the knee joint axis was alignedwith the axis of the power head. Limits were then set at 0 0 and 90 0 flexion. Theangular velocity was set at 90 0 /sec. Each subject had 6 sub-maximal repetitions as awarm up and during data collection verbal instruction was strictly standardised. Theconcentric peak extension torque was recorded.161

____________________________________________________________Chapter 88.3.4 Muscle FatigueFatigue indices of the vastus medialis oblique (VMO), vastus lateralis (VL), and rectusfemoris (RF) were assessed by bipolar electrode surface electromyography (EMG).Skin preparation, electrode placement and patient position were an exact replicationof the reliability study in Chapter 5. The raw signal was captured and analysed via aTEL100M four channel remote amplifier/transmitter system (Biopac Systems Inc.California USA). This was to a TEL100D receiver module and a MP100 acquisitionunit. EMG signals were high pass (8Hz) and low pass (500Hz) filtered (Butterworthfilter), with a sharp notch (Band stop) filter of 50Hz filter to remove DC noise. Theamplifier was set with a gain of 10, a Common Mode Rejection Ratio (CMMR) of 110-dB minimum and a signal-to-noise ratio of 65dB minimum. There was a differentialinput impedance of 2MΩ. The signal was analogue to digital converted at a samplingrate of 1024 Hz. The EMG signal was on-line analysed by a graphical programminganalysis system (LabVIEW TM5.0, National Instruments, Texas, USA), in order tocontinuously derive the MF of the power density spectrum every second, during asustained 60 second contraction at 60% MVIC, using a Fast Fourier Transform (FFT)algorithm. Median frequency was normalised against initial median frequency and alinear regression was constructed over the contraction time of 60 seconds from whicha slope was derived to express the fatigue rate 296;297 .162

____________________________________________________________Chapter 88.3.5 Quadriceps Cross Sectional AreaCSA was assessed as part of the inclusion criteria, and immediately post stimulation.In an exact replication of the reliability study in Chapter 7, a static B compoundultrasound scanner (Technicare EDP 1200) was used with 5 and 2.25 MHztransducers. Scans were taken at the thigh mid point between the lateral joint line ofthe knee and the greater trochanter. This was marked on an acetate sheet in order toensure exact reproduction of the position for the post treatment scan. A hard copy ofeach scan was obtained and the area of the quadriceps calculated using the Digiteyesoftware (Medical Physics Dept. Hope Hospital, Salford UK) (see Figures 25, 26 and27 in Chapter 7).8.3.6 FunctionThis was assessed using the Kujala Patellofemoral Score. This is a self reportedquestionnaire scoring system with values ranging from 100 (a normal, painless, fullyfunctioning knee) to 0 at the other extreme of the scale (severe knee pain anddysfunction). It has been found to be valid and reliable in the measurement of functionin PFPS 283 .163

____________________________________________________________Chapter 88.3.7 PainPatellar pain on the day of assessment was assessed by use of a visual analoguescale 279comprising a 10 cm line with 0 cm representing no pain and 10 cmrepresenting worst pain ever.8.3.8 Clinical testsIn addition, the following commonly used clinical tests were employed to ascertain ifimprovement or deterioration in the physiological and pain tests of lower limb functionwere also apparent in the simpler yet functional important movements. These testsform part of a dynamic evaluation of muscle action, symptomology and treatmenteffectiveness in PFPS 89 :8.3.8.1 Step upThe number of steps the patient could perform up onto a 25cm step until the onset ofpatellar pain.8.3.8.2 Step downThe number of steps down a 25cm step the patient could perform until the onset ofpatellar pain. The common activities of ascending and descending steps have beenused in previous studies involving patients with PFPS 10;71;72 .164

____________________________________________________________Chapter 88.3.8.3 Squat flexionThe amount of knee flexion patients could achieve from a standing position until theonset of their patellar pain. This was measured in the standard way by a universalgoniometer, aligned with the greater trochanter, through the lateral joint line to thelateral malleolus 298 .8.4 TreatmentPatients were randomly allocated by computer program to either the RESTIM orCOMPEX treatment regimes.8.4.1 RESTIMThis was a two-channel portable pre programmed stimulator (DMI Ltd. Wigan, UK)that produced a balanced, asymmetrical biphasic pulse to a maximum of 90mA with aduty cycle of 10:50, and the pulse duration was set at 200µs as frequently adopted inhuman studies in muscle 166;299 . Stimulation parameters were controlled by anerasable programmable read only memory microchip (EPROM 2764) which wereprogrammed using a specifically written computer software (CHAMP DMI, WiganU.K.) and a microchip programmer (Dataman S3). This stimulation pattern consistedof three simultaneously delivered components: a background low frequencycomponent, a high frequency component superimposed on the background at regularintervals and a 'doublet' of pulses 23 delivered within the higher frequency burst. This165

____________________________________________________________Chapter 8new pattern of stimulation has been used previously in the treatment of the humanpelvic floor muscles 300 .Patients were instructed in the placement of the two self-adhesive electrodes(10cmx17cm – total area 340cm 2 : Chattanooga, TN, USA; Figure 32), in the use ofthe device and were given an information sheet. Stimulation took place for one houreach day, every day for six weeks.8.4.2 COMPEXThis stimulator was a commercially available 3 channel model (Medicompex SA,Switzerland), which generated bipolar, biphasic, asymmetrical rectangular pulses.The treatment sequence specified in the instruction manual for PFPS, was once aday five days a week for the first two weeks (2 minutes at 8Hz pulse width 250 µs; 20minutes at 35 Hz; duty cycle 6s at 35Hz then 8s ’rest’ at 8Hz = 2353 impulses /min,pulse width 350µs; 3 minutes at 3Hz pulse width 250µs). Then three times a week forweeks 3 and 4 and twice a week for the last two weeks ( 2 minutes at 8Hz pulse width250 µs;20 minutes at 45Hz pulse width 350 µs; 3 minutes at 3 Hz pulse width 250µs). Placement of the COMPEX electrodes (4 x 5cmx5cm and 1 x 10cmx5cm totalarea 150cm 2 ) was demonstrated to the patients.All treatment sessions for both stimulators took place at home and patients wereasked to fill out a compliance diary to state each day if stimulation had taken place ornot. Patients were also asked to continue with their normal daily activities. The166

____________________________________________________________Chapter 8treatment period of six weeks was chosen for several reasons. The overwhelmingconsensus gleaned from the literature in previous studies used six weeks treatmentperiods. Consequently, this is a typical clinical regime used by physiotherapists.Additionally, there is evidence from the literature using continuous stimulation that theeffects are, in the main, complete by six weeks 24;128;183 , which seems to obviate theneed for a longer period. Stimulation commenced the day after the final pre testassessment. The first post treatment assessment took place within three days ofcompleting stimulation. A flow diagram of the study protocol can been seen in Figure29.8.5 Statistical AnalysisData were tested and found to be normally distributed using the Kolmogorov -Smirnovtest. The mean pre and post differences were calculated and descriptive statisticsproduced. Statistical analysis was conducted initially using a 3 factor repeatedmeasures analysis of variance (ANOVA). The following variables were included in theanalysis: time (pre stimulation v post stimulation) and reading (3 readings pre, 3readings post) as within subjects factors. Group (RESTIM or COMPEX), was includedas a between subjects factor. Further within group comparisons using mean pre andpost scores were made using paired ‘t’ tests. For quadriceps muscle endurance data,the normalised slope coefficients of all three muscles were analysed by a repeatedmeasures ANOVA with the variables of time (pre and post stimulation) and group(RESTIM or COMPEX). These data were also graphically represented by a method167

____________________________________________________________Chapter 8whereby pre treatment median frequency slopes are normalised to zero 297 . This isdone in order to control for the differences in responses between individuals prior totreatment. Any post treatment changes were then expressed as the difference fromthis normalised value. A value of p

____________________________________________________________Chapter 8REFERRED TO TRIALn =30U/S SCANn = 7 excludedEXAMINATIONn = 2 excludedGAITn = 5 excludedTOTAL EXCLUDEDn = 14PATIENTS REGISTEREDn = 16RANDOMISATIONPRACTICE ASSESSMENTPRE ASSESSMENT 1PRE ASSESSMENT 2RESTIM 6 WEEKSn = 8WITHDRAWNn =1PRE ASSESSMENT 3START STIMULATIONSTOP STIMULATIONPOST ASSESSMENT 1n = 14COMPEX 6 WEEKSn = 8WITHDRAWNn =1POST ASSESSMENT 2POST ASSESSMENT 3169

____________________________________________________________Chapter 8Figure 29 Flow diagram of the Pilot study protocolTable14 Muscle strength, pain and functional data. Means ±SD of mean changes.Raw score and mean percentage change between pre and post stimulationRESTIMPre-stim Post-stim Mean Change Mean % P valuein raw score change frombaselineIsometric (Nm) 66.2 ± 19.4 79.4 ± 27.7 13.3 ± 15.1 19.5% 0.059Isokinetic (Nm) 94.6 ± 36.2 106.3 ± 41.7 11.7 ±7.2 12.3% 0.005 *PAIN (points) 5.3 ± 1.6 3.8 ± 1.8 -1.5 ±2.0 -24.3% 0.094STEPS (No.) 13.6 ± 12.6 18.7 ± 14.9 5.1 ±6.0 69.5% 0.065FLEXION (degrees) 98.6 ± 40.6 109.5 ± 30.8 11.0 ± 28.4 30.6% 0.346KUJALA (points) 61.3 ± 8.4 67.0 ± 10.4 5.2 ± 10.3 9.5% 0.232CSA (cm 2 ) 20.6886 ±20.6300 ±-0.0586 ±-0.0519% 0.6036.4716.3460.282COMPEXPre-stim Post-stim Mean Change Mean % P valuein raw score change frombaselineIsometric (Nm) 70.7 ± 30.8 76.5 ± 28.1 5.9 ± 4.9 13.1% 0.019 *Isokinetic (Nm) 93.6 ± 26.1 100.2 ± 27.0 6.7 ± 16.4 9.7% 0.323PAIN (points) 4.6 ± 1.8 3.4 ± 2.3 -1.2 ± 1.9 -30.0% 0.133STEPS (No.) 8.1 ± 2.8 14.2 ± 8.5 6.1 ± 7.6 76.4% 0.077FLEXION (degrees) 98.8 ± 21.9 95.7 ± 17.6 -3.1 ± 12.7 -2.0% 0.544KUJALA (points) 65.4 ± 11.6 72.9 ± 9.1 6.7 ± 16.4 12.7% 0.045*CSA (cm 2 ) 17.9829 ± 17.9800 ± -0.0029 ± -0.1815% 0.989170

____________________________________________________________Chapter 82.218 1.854 0.5488.6.1 Isometric StrengthThere were no statistical differences between the RESTIM and COMPEX groups priorto stimulation ( t = -0.326 p=0.75). The repeated measures ANOVA showed no groupor reading effect but a significant time effect (p=0.018) (Table 15). When analysedseparately with a Paired 't' test, an improvement between pre and post measuresreached statistical significance for COMPEX (p=0.019) but not for RESTIM (p=0.059)(see Table 14).Table 15 Results of Repeated Measures ANOVAfor Muscle strength, pain and functional outcomes.EFFECT Group Time ReadingF p F P F Pisometric (Nm) 0.01 0.921 7.79 0.018* 0.59 0.565Isokinetic (Nm) 0.002 0.966 6.02 0.032* 2.10 0.150PAIN (points) 0.16 0.701 6.45 0.027* 0.41 0.668STEPS (Number) 0.07 0.794 8.80 0.013* 0.87 0.433FLEXION (degrees) 0.002 0.966 0.52 0.487 0.41 0.669KUJALA (points) 1.64 0.226 8.62 0.014* 1.24 0.309171

____________________________________________________________Chapter 88.6.2 Isokinetic strengthThere were no differences between the RESTIM and COMPEX groups prior tostimulation (t=0.059; p=0.954). There was a significant time effect (p=0.032) (Table15). When analysed separately only the RESTIM group showed a significantimprovement between pre and post measures (p=0.005) (Table 14).8.6.3 Muscle FatigueFigure 30 graphically represents the data as means ±SD that shows a slight increasein the RF average median frequency slope of 1.1± 8.1 for COMPEX and 1.8 ± 11 forRESTIM. For VL there was an increase in the average median frequency of 2.4± 3.9for COMPEX and 3.2 ± 4.9 for RESTIM. For VMO there was a decline in the averagemedian frequency slope of 5.9 ± 9.1 for COMPEX. On the other hand there is only a2.5 ± 6 decline for VMO for RESTIM. Table 16 shows the repeated measures ANOVAfor the three muscles. There were no significant time or group effects for VMO, VLand RF. Table 17 shows the means of % rate of change per second for the threemuscles pre and post stimulation.172

____________________________________________________________Chapter 8Figure 30. Mean ± SD Plots of median frequency slope differences(%/s)(pre-stim / post-stim) for VMO, VL. and RF at 60% MVIC 60s contraction.173

____________________________________________________________Chapter 8Table 16 Repeated Measures ANOVA for quadriceps muscle fatigue data.EFFECT Group TimeF p F PVMO 0.688 0.425 0.533 0.480VL 0.075 0.790 0.006 0.939RF 0.000 0.991 0.473 0.506Table 17 Quadriceps muscle fatigue data.Group means of %rate of change per secondRESTIMCOMPEXPre stim Post-stim Pre stim Post stimVMO -0.082 -0.085 -0.138 -0.183VL -0.1011 -0.072 -0.084 -0.31RF -0.111 -0.144 -0.119 -0.538.6.4 Quadriceps Cross Sectional AreaThere were no significant differences between RESTIM and COMPEX groups prior tostimulation (t=1.046; p=0.316). As there was only one reading pre and poststimulation, this was analysed solely by ‘t’ tests. There were no statistically significantdifferences in the pre and post stimulation CSA values for RESTIM (p=0.603) andCOMPEX (p=0.989). As both groups had extremely small values with negligibledifferences, the means were reported to four decimal places and standard deviationsto three decimal places (Table 14).174

____________________________________________________________Chapter 88.6.5 FunctionThere were no significant differences in the Kujala scores between RESTIM andCOMPEX groups prior to stimulation (t=-1.03; p=0.323). There was significant timeeffect (p=0.014). When analysed separately there was a significant differencebetween the pre and post stimulation values in the COMPEX group (p=0.045).(Tables 14 and 15)8.6.6 PainThere were no differences between the two groups prior to stimulation (t=0.775;p=0.453). There was a significant time effect (p=0.027), indicating that all the patientsimproved with treatment. But when analysed separately the improvement for painscores did not reach statistical significance for either group (RESTIM p=0.09;COMPEX p=0.13) (Tables 14 and 15).8.6.7 FlexionThere were no significant differences between RESTIM and COMPEX groups prior tostimulation (t = -0.014; p=0.989). The repeated measures ANOVA showed nosignificant effects due to time, group, or reading post stimulation (Table 15).175

____________________________________________________________Chapter 88.6.8 StepsThere were no differences between the RESTIM and COMPEX groups prior tostimulation (t=1.13 p=0.280). Both groups showed a significant time effect in thenumber of steps (p=0.013) but separate analysis no significance between the groups(RESTIM p=0.065; COMPEX p=0.077) (Tables 14 and 15).8.7 DiscussionIn order for a muscle to operate to optimum efficiency it requires both strength andendurance characteristics. Existing electrical muscle stimulation is designed toproduce either low or high frequency stimulation. This is problematic as lowfrequency stimulation is used to increase fatigue characteristics of a muscle, but atthe expense of power generation 23 . On other hand, if stimulation is used to increasepower this is at the expense of endurance 32 . A combination of these two elementshas been attempted in sequential stimulation regimens like COMPEX wherebyperiods of low-frequency stimulation have been followed by high-frequency periods orvice-versa. This is a non-physiological approach to stimulation as motor nerve firingpatterns usually address both factors simultaneously.The RESTIM regimeaddresses this by delivering low and high frequency to the muscle simultaneously,thus combining the development of strength and fatigue characteristics. The efficacyof this approach has been tentatively evaluated in this Pilot study on the quadricepsof 14 patients with patellofemoral pain syndrome, with outcome assessed using bothphysiological and functional measures. Large variances may explain why some176

____________________________________________________________Chapter 8improvements in strength and function, as indicated by percentage change, onlyshow borderline statistical significance (Table 14). Both regimes improved quadricepsstrength as measured by MVIC and peak torque that concurs with previous studies onPFPS 30;138 . The lack of increased cross sectional area of the quadriceps also concurswith a previous study using similar stimulation parameters and protocols onosteoarthritic knees 292 . There were statistically significant within-group poststimulation improvements in the physiological measures of isometric and isokinetictorque, but not between the groups. The large variance in the measures may accountfor improvements in the raw data (for example for RESTIM stimulation a 19.5%improvement in isometric strength) not being reflected by statistical significance.Regarding the fatigue data, numerous investigations have focussed on EMGamplitude and onset on activity rather than fatigue rates of the VMO relative to the VLand the RF, with differing methodologies causing contradictory results 301 . It has beenproposed that fatigue rates of VMO may be lower than VL in PFPS 302 . So far, the useof power spectral analysis using a median frequency slope has shown no selectivefatigue at 30% or 60% MVIC in the VMO and VL normal subjects 84 , but lower fatiguerates (i.e. greater fatigue) of VMO over VL in patients with anterior knee pain 303 . InPFPS, the contribution of VL and RF are not considered to be as important as VMOdue to the role of the latter in maintaining patella stability 29;50;304 . The effects ofRESTIM on endurance characteristics of VMO were therefore of interest in this groupof patients. Roy et al. 297 plotted the interaction of surgery and time on the MF slope177

____________________________________________________________Chapter 8from the lumbar extensor musculature of patients with low back pain. They indicatedthat a less negative MF slope may be interpreted as an”improvement” in the patients’endurance characteristics. As mentioned previously, the increase in strength withconventional EMS is accompanied by a decrease in endurance. This was alsoobserved in the present study using COMPEX stimulation where decrease inendurance was observed in the VMO (Figure 30 and Table 17). RESTIM on the otherhand seems to protect against this by limiting the decrease, thus supporting the useof simultaneous mixed frequency stimulation. This protection mechanism has notbeen reported previously, but caution is urged because although Table 17 indicatessome interesting effects on endurance characteristics that are useful to report, theresults from the repeated measures ANOVA (Table 16) are not significant.Whilst both groups demonstrated improvements in the raw data for steps, KujalaPatellofemoral score, pain and knee flexion statistical differences between RESTIMand COMPEX were not apparent despite differences in physiological indices.8.8 LimitationsThere are some limitations worth highlighting in this study. First, is the difference inthe treatment regimes between RESTIM and COMPEX. The regime for COMPEXwas exactly that as specified in its manual for PFPS. It was considered unethical tochange prescribed regimes for this specific condition, even though this would mean adissimilar treatment period. The regime for the RESTIM was the same as previousstudies on the weakened pelvic floor musculature of women using the same178

____________________________________________________________Chapter 8simultaneous mixed frequency parameters 300 . The second issue is that of samplesize. This trial was initiated as a Pilot study, in an attempt to assimilate informationabout the protocol, the outcome measures and to form the basis of the Main study. Assuch a power sample calculation was considered inappropriate and this limitation isacknowledged.8.9 ConclusionsThis Pilot study has indicated on patients with patellofemoral pain that electricalstimulation of the quadriceps can improve isometric and isokinetic strength, pain, selfreporting function, and step testing. There were no significant differences between thetwo types of stimulation any of the outcome measures. There is some indication thatthe RESTIM device, a simultaneous mixed frequency regime, seems to protectagainst loss of fatigue resistance that was not as easily observed in the COMPEX, acommercially available sequential mixed frequency device.8.10 Considerations for the Main StudyAs a result of this phase of the study, certain considerations and recommendationswere made prior to the Main study.Firstly, the results from the repeated measures ANOVA showed no significantdifferences between the three pre treatment assessments for all the outcomemeasures and no significant differences between the three post treatment179

____________________________________________________________Chapter 8assessments. A decision was made based on this statistical information to assessonly once post treatment. Two assessments (including a full practice session) wouldbe performed prior to treatment in order to establish a pre treatment baseline level ofassessment.Secondly, it was noted that many patients with PFPS were not considered for thestudy from orthopaedic clinics because the patients had PFPS for longer than 3years. Other randomised studies have not specified a length of time for their patientswith PFPS 284;305 . It was decided that this criterion was too short and so that manysuitable patients otherwise might be included in the Main study, this duration periodwas lengthened to 10 years.Another consideration was that the acknowledged type 2 statistical error due to thesmall sample size in the Pilot study may be avoided in the Main study now thatinformation was available to calculate the appropriate sample size. The fact that noother EMS study on the same patient group was of sufficient quality to calculate theappropriate sample size confirmed the usefulness of the Pilot study in producing thisfigure.A decision was made to compare the RESTIM device with another commerciallyavailable stimulator, the EMPI described below in section 9.2.1. This device was usedrather than the COMPEX stimulator because it was deemed important to havematching periods of stimulation (i.e. 60 minutes). In addition, the EMPI stimulator wasconsidered a market leader in the USA for the treatment of skeletal muscle byelectrical stimulation. This raised the issue of the likelihood of differences between the180

____________________________________________________________Chapter 8performances of the COMPEX and EMPI devices and the implications forgeneralisation from the Pilot study to Main study. Although, essentially, the samefrequencies were involved in both COMPEX and EMPI, the duty cycle parameterswere different resulting in 2353 impulses/min being delivered to the muscle byCOMPEX and 350 impulses/min by EMPI. The literature debates whether it is thetotal number of impulses delivered rather than just the frequency per se that is themost important parameter when stimulating muscle 193 . The difference in the numberof impulses between COMPEX and EMPI may have been large enough to suggestthat differences would be seen between the two devices. Furthermore, the COMPEXand EMPI were also different in terms of stimulation time. It has been clearly stated inthe literature that the length of time of stimulation also has a profound effect onmuscle physiology 96 . RESTIM was developed with a daily treatment session of 60minutes, whereas the COMPEX protocol for PFPS only demanded a maximum of 25minutes daily. Therefore, the Main study would employ the EMPI device that had a 60minutes treatment protocol for PFPS thus providing a better comparison with RESTIMand removing stimulation time as a confounding variable. These differences highlightthe issues of generalisation from the Pilot study to the Main study. However, usingone device to generalise to another can be justified in light of the fact that the Pilotstudy and the Main study would be conducted on the same patient group, from thesame referral sources, using the same equipment to produce the same outcomemeasures, with the same mode of treatment (i.e. a comparison of EMS with EMS, nota comparison of EMS with voluntary exercise), for the same period of time.181

___________________________________________________________Chapter 9Chapter 9THE MAIN STUDY182

___________________________________________________________Chapter 99 MAIN STUDY9.1 IntroductionHaving completed the Pilot study, appropriate sample size calculations could now bemade, and the mechanics and protocol of the test procedures were adjusted in thelight of experience gained in the Pilot study in Chapter 8.The Main study, therefore, was instigated to compare the RESTIM with the EMPIstimulator. The research design was that of a double blinded randomised, controlledtrial. The null hypothesis was that there would be no statistical differences betweenthe two devices.9.2 Methodology9.2.1 The RESTIM stimulation regimeThe stimulation pattern, frequency and pulse width for the RESTIM device was thesame as the Pilot study, incorporating mixed frequency patterns of stimulation with a‘doublet’ of pulses at the beginning 23 . This was a two-channel portable preprogrammed stimulator that produced a balanced, asymmetrical biphasic pulse to amaximum of 90mA with a duty cycle of 10:50. The pulse duration was set at 200µs asfrequently adopted in human studies in muscle 166;299 . The RESTIM* device used inthe Main study was manufactured specially (Smith & Nephew plc, York, UK). It used amathematically derived pattern that consisted of the following interpulse intervals:183

___________________________________________________________Chapter 98ms, 12ms, 20ms, 20ms, 20ms, 20ms, 400ms, 500ms that can be illustrated asfollows:8ms 12ms 20ms 20ms 20ms 20ms 400ms 500ms1000ms (1second)Figure 31. Stimulation pattern for the RESTIM device.Note the ‘doublet’ at the beginning of the pulse train.With a duty cycle of 10:50 the pattern delivered 90 impulses /min to the quadriceps.Patients were shown how to use the device by a different physiotherapist investigatorin order to preserve the blinding for the study. All aspects of the device wereexplained and the electrode positions were demonstrated on the patient’s thigh.Two self-adhesive electrodes (10cmx17cm – total area 340cm 2 : Chattanooga, TN,USA) were used. Patients were instructed to maintain knee extension and not to walkor do other activities during stimulation. This was to ensure equality of muscle lengthduring stimulation and to minimise the influence of stretch on patients’ quadriceps 146 .An information sheet was given to the patient (see Appendices) and a diagram forelectrode position to ensure correct placement (Figure 32) as well as the compliancediary. One of the specifications of the RESTIM devices was an inbuilt compliance* RESTIM is a working product title for the device and is not a trademarked name184

___________________________________________________________Chapter 9monitor that would provide information on the date and time of day, the period of timeand the amplitude setting for each treatment session. This was accessed after the 6weeks treatment period by the physiotherapist investigator blinded to the pretreatment test results.Figure 32 Electrode placement (in white) for the RESTIM stimulator185

___________________________________________________________Chapter 99.2.2 The EMPI stimulation regimeThe EMPI device was commercially available (EMPI Inc.,Mn., U.S.A.) and had atreatment protocol for PFPS. This protocol consisted of daily stimulation periodslasting 60 minutes with a fixed frequency of 35Hz. Similar to the RESTIM, it used aasymmetrical biphasic rectangular waveform with pulse duration set at 300µs, with amaximum amplitude set at 100mA. The pattern can be illustrated as follows:28ms 28ms 28ms 28ms 28ms 28ms 28ms 28msFigure 33. Stimulation pattern for the EMPI device1000ms - - - - - - -With a duty cycle of 10:50, this fixed frequency delivered 350 impulses to thequadriceps muscles every minute.Once again, the device was fully explained to and demonstrated on the patients bythe same physiotherapist investigator. A diagram of electrode placement was given(Figure 34). Four self adhesive electrodes were used (EMPI Inc. USA. 5cmx9cm: totalarea 180cm 2 ) Patients were instructed to maintain knee extension as for the RESTIMdevice. Once the patients were confident and competent in its use, they were giventhe compliance diary. Both devices were given to the patients for 6 weeks. Therationale for this treatment period was explained in the Pilot study in section 8.4.186

___________________________________________________________Chapter 9Figure 34 Electrode placement (in white) for the EMPI stimulator187

___________________________________________________________Chapter 9Figure 35 The RESTIM device and electrodesFigure 36 The EMPI device and electrodes188

___________________________________________________________Chapter 99.2.3 Sample power calculationsOne benefit of the Pilot study was that it allowed an investigation into sample powercalculations with a relevant population using methods of measurement that would beutilised in the Main study. Sample power calculations were performed in order toassess the number of subjects that would be required to see statistically significantdifferences between the two groups in the Main study. With pain, measured using aVAS, as the main outcome measure, the observed difference between RESTIM andCOMPEX in the Pilot study was –0.5 units (±SD 2.3) (Table 14). It was consideredunfeasible to recruit this number of patients for each group therefore isokineticstrength was chosen as the main outcome. Other outcomes were then used (MVIC,peak torque and quadriceps fatigue). The sample size calculations were moreacceptable (see Table 18), putting the power of the study at 85% with 40 subjects pergroup (P < 0.05). The Main study was approved by the ethics committee of theCentral Manchester Health Care Trust.Table 18 Sample Size Calculationspoweroutcome observed ±SD 80% 85% 90%differencepain -0.5 2.3 335 383 448isometric 6.3 (Nm) 8.05 27 31 36isokinetic 7.5 (Nm) 10.92 35 40 46fatigue 17.9 (Hz) 24.87 32 36 42189

___________________________________________________________Chapter 99.2.4 Subjects9.2.4.1 Inclusion CriteriaThese criteria were similar to the Pilot study in Chapter 8, with the exception of theduration period, which was changed to greater than six months and not longer than10 years and the use of 4% difference in quadriceps CSA between limbs that was notapplied.9.2.4.2 Exclusion CriteriaThese criteria were replicated from the Pilot study in Chapter 8,9.2.4.3 Clinical examinationThis was performed in the same way as the Pilot study in Chapter 8.9.2.5 RandomisationTo ensure broadly comparable groups with regard to baseline variables of gender andbody mass index patients were stratified from one of four groups (Male; Female, BMI:≤ 26, BMI: >26), upon entry into the trial. Randomisation was performed by consultingfour computer generated randomisation lists, one for each of the four stratifiedgroups. Patients were randomised into the two treatment groups after they hadsigned the consent form and had formally entered the study. The randomisation listprovided a trial number on which was based the corresponding treatment group (i.e.RESTIM or EMPI). The lead investigator who was examining and measuring the190

___________________________________________________________Chapter 9patients was not part of the randomisation process, thus ensuring blindness to thestimulator allocation.9.3 Outcome measures9.3.1 InstrumentationIsometric and isokinetic concentric extension torque of the lower limb was measuredusing the Biodex system 2 isokinetic dynamometer (Biodex systems Inc. Shirley N.Y.USA) with a closed kinetic chain attachment as supplied by the manufacturers. Thisattachment has been assessed for extension test –retest reliability in PFPS patientswith ICC estimates 0.92 for isometric mode and 0.85 for isokinetic mode in Chapter4 269 . The closed kinetic chain (CKC) method was chosen in preference to thestandard isokinetic lever arm as previously described in Chapter 4 and the Pilot studyin Chapter 8. CKC exercise has been advocated for patients with PFPS due to alessening of the patellofemoral joint reaction force and patellofemoral stress 222 . It wasdemonstrated that there were significantly fewer stresses at the patellofemoral joint atthe most functional range of movement during a leg press (CKC) exercise than a legextension (OKC) exercise. A CKC method of assessment may not only bring aboutobjective changes, but also lead to improvement in perceived function inpatellofemoral pain syndrome 223 . Static and dynamic measures of extension torquewere adopted in the Main study because the use of the two testing modes gave acomprehensive assessment of muscle function. An isometric test was needed191

___________________________________________________________Chapter 9because the patients stimulated their quadriceps muscles in a static position.Previous authors 284had highlighted the problems of a testing protocol being adifferent nature to the exercise protocol, especially in terms of angular velocity. Theuse of an isometric test for an isometric treatment would help remedy this. Secondly,despite the isometric nature of the EMS, an isokinetic test was needed as this mayhave helped quantify any association of EMS on the dynamic, functional tests such assteps and knee flexion.9.3.2 Isometric StrengthSubjects were positioned in the Biodex chair with the hip at 90 0 flexion and the kneeangle at 45 0 flexion. This positioning is an exact replication of the reliability study inChapter 4 and the Pilot study in Chapter 8. This angle had been determined in otherstudies as the most appropriate to reduce patellofemoral stress to a minimum duringtesting 222 . To ensure that the subjects maintained the 45 0 angle, the operator placeda hand under the knee to act as a popliteal pad. Subjects pushed into the foot platewithout lowering the popliteal surface of the knee into the operator's hand (and thusbeyond 45 0 ). Subjects had practice contractions prior to data collection to familiarisethemselves with this method and to ensure that they were able to maintain a kneeangle of 45 0 . Twitch interpolation was used to overcome central fatigue and ensure amaximum voluntary isometric contraction 140 . Subjects performed three maximumcontractions of 10 seconds duration with 2 minutes rest between each. Theconcentric peak extension torque was recorded.192

___________________________________________________________Chapter 99.3.3 Isokinetic torqueIn an exact replication of positioning in the reliability study in Chapter 4, subjects wereplaced in the chair with hip flexion set at 90 0and the shoulder and waist strapsapplied. The foot was placed flat against the foot plate attachment and was held inplace by velcro straps. With the knee at full extension the knee joint axis was alignedwith the axis of the power head. Limits were then set at 0 0 and 90 0 flexion. Theangular velocity was set at 90 0 /sec. Each subject had 6 sub-maximal repetitions as awarm up and during data collection verbal instruction was strictly standardised. Theconcentric peak extension torque was recorded.9.3.4 Muscle FatigueFatigue indices of the vastus medialis oblique (VMO), vastus lateralis (VL), and rectusfemoris (RF) were assessed by bipolar electrode surface electromyography (EMG).Skin preparation, electrode placement and patient position were an exact replicationof the reliability study in Chapter 5 and the Pilot study in Chapter 8. Using a TEL100Dreceiver module and a MP100 acquisition unit, EMG signals were high pass (8Hz)and low pass (500Hz) filtered (Butterworth filter), with a sharp notch filter of 50Hz filterto remove DC noise. The amplifier was set with a gain of 10, a Common ModeRejection Ratio (CMMR) of 110-dB minimum and a signal-to-noise ratio of 65dBminimum. There was a differential input impedance of 2MΩ. The signal was analogueto digital converted at a sampling rate of 1024 Hz. The EMG was subjected to FastFourier Transform to extract the median frequency calculated at 1 second intervals193

___________________________________________________________Chapter 9during a sustained 60 second contraction at 60% MVIC. MF was normalised againstIMF and a linear regression was constructed over the contraction time of 60 secondsfrom which a slope was derived to express the fatigue rate 296;297 .9.3.5 Quadriceps Cross Sectional AreaCSA was assessed pre stimulation and immediately post stimulation. The techniquereplicated exactly the procedures described in Chapter 7 and the Pilot study inChapter 8. Briefly, a static B compound ultrasound scanner (Technicare EDP 1200)was used with 5 and 2.25 MHz transducers. Scans were taken at the thigh mid pointbetween the lateral joint line of the knee and the greater trochanter. This was markedon an acetate sheet in order to ensure exact reproduction of the position for the posttreatment scan. A hard copy of each scan was obtained and the area of thequadriceps calculated using the Digiteye software (Medical Physics Dept. HopeHospital, Salford UK).9.3.6 FunctionThis was assessed using the Kujala Patellofemoral Score. This is a self reportedquestionnaire scoring system with values ranging from 100 (a normal, painless, fullyfunctioning knee) to 0 at the other extreme of the scale (severe knee pain anddysfunction). It has been found to be valid and reliable in the measurement of functionin PFPS 283 .194

___________________________________________________________Chapter 99.3.7 PainPatellar pain on the day of assessment was assessed by use of a visual analoguescale 279comprising a 10 cm line with 0 cm representing no pain and 10 cmrepresenting worst pain ever.9.3.8 Clinical testsIn addition, the following commonly used clinical tests were employed to ascertain ifimprovement or deterioration in the physiological and pain tests of lower limb functionwere also apparent in the simpler yet functional important movements:9.3.8.1 Step upThe number of steps the patient could perform up onto a 25cm step until the onset ofpatellar pain.9.3.8.2 Step downThe number of steps down a 25cm step the patient could perform until the onset ofpatellar pain.9.3.8.3 Knee FlexionThe amount of knee flexion patients could achieve in squatting until the onset of theirpatellar pain. This was measured in the standard way by a universal goniometer,aligned with the greater trochanter, through the lateral joint line to the lateralmalleolus.195

___________________________________________________________Chapter 99.4 Statistical analysisStatistical analyses were performed using SPSS (Statistical Package for the SocialSciences) for Windows (v.9). A value of p0.05) for all parameters except Pain (p=0.001) and Steps (p =0.02). Therefore all data were analysed using parametricstatistics except these two measures which were analysed with non parametricequivalents.9.4.2 Pre Treatment AnalysisComparisons were made between the groups prior to treatment using independent ‘t’tests for all outcome measures, but Mann Whitney-U tests for pain and stepsoutcomes.9.4.3 Post Treatment AnalysisThe post treatment differences between the groups were analysed using independent‘t’ tests for normally distributed data or Mann Whitney-U tests if the data did notdemonstrate normal distribution. If significances were found then pre and post196

___________________________________________________________Chapter 9treatment analyses were performed within each group using paired ‘t’ tests orWilcoxon Signed Ranks tests. A repeated measures analysis of variance (ANOVA)was also used to ascertain time, group effects and group / time interactions for eachoutcome. Factors for this were Time (pre stimulation v post stimulation) as a withinsubjects factor and Group (RESTIM or EMPI) as a between subjects factor. Althoughit is not normal statistical procedure, within group differences were analysed withpaired ‘t’ tests in the absence of between group differences in order to facilitate thediscussion comparing the two EMS devices.9.4.3.1 Multiple Regression AnalysisIn order to examine the simultaneous effect of multiple covariates on the each posttreatment outcome, a more detailed analysis was performed using a multipleregression analysis. There are no strict rules for selecting predictor variables, andpast experience or clinical knowledge may be sufficient to keep a variable in themodel 306 . Thus a subjective assessment may be necessary when trying to find thebest model 306 . However, this did not preclude a logical procedure in order todetermine the most appropriate variables for the multiple regression models. Firstly, atheoretical model was derived based on previous studies and the literature on PFPS.For example, in their study on non operative treatment for PFPS Kannus andNiitymaki 14used age, gender, BMI and duration of symptoms and so these wereconsidered. Next, the relationship between the dependent variable and predictorvariables was determined by a Pearson product moment correlation coefficient. Thus,197

___________________________________________________________Chapter 9correlation coefficients were also used to ascertain if there were any other variables,of which there was little prior information, which could be added to the model using acut off confidence value of p>0.05 306 . As it is not advisable to perform correlationsbetween continuous and dichotomous data 14 , the influence of each of the latter oneach dependent variable was determined by ‘t’ tests. Dichotomous data in the Mainstudy were gender (male, female) treatment group (RESTIM, EMPI), and the kneeside tested (left, right). Each of the post treatment outcome measures acted as adependent variable with the other outcomes acting as predictor (or independent)variables.Finally, once the variables had been established for the model, multiple regressionanalysis was performed using both direct and stepwise regressions. Direct regressionentered all the predictor variables at the same time. This gave an R 2 value to thetheoretical model. The R 2 and adjusted R 2 are measures of the correlation betweenthe observed and predicted value for the dependent variable and as such indicateshow well the model predicts the dependent variable 306 . The adjusted R 2 was reportedas this can compensate for the expected chance prediction when the null hypothesisis true and is thus more appropriate 306 . In order to select the important predictors fromthe theoretical model, a stepwise regression procedure was performed. This added ina new predictor variable to the model and a new relationship between the dependentvariable and the predictor (independent) variables was re-evaluated. In this way itwas possible to see if the new predictor variables improved the fit of the model and to198

___________________________________________________________Chapter 9see if the predictor variables already present were still significantly contributing to themodel when new variables were added 307 .If a model had a low adjusted R 2 value, an attempt to improve it was made by lookingat the inter-relationships between predicting variables. By calculating an interactionterm between two variables (either continuous or dichotomous) and obtaining theirproduct, a new variable was created and added to the model. The results of addingthe new variable are reported for each outcome measure with a low adjusted R 2value.One of the assumptions of regression analysis is that the residuals for consecutiveobservations are uncorrelated or independent 308 . Although the R 2 value is used todescribe how well the model fits the data 306 , there is also a need to check thedistribution of the residuals for normality. This is best achieved by using simple visualdiagnostics of the plots of the residuals. If the data for the model are a good fit, thenthe data points should be be evenly scattered along the line and a histogram of thesedata will reveal a normal distribution shaped curve. The Durbin-Watson test providesa formal test of normality for autocorrelated observations, although this should beviewed in light of the conflicting arguments surrounding visual and statisticalanalysis 308 . If the assumption for uncorrelation is true then the expected value for theDurbin-Watson statistic is 2. Values less than 2 indicate that positive autocorrelationand less than 2 are negatively autocorrelated. Both these methods were used foreach of the multiple regression models.199

___________________________________________________________Chapter 99.4.3.2 Treatment Effect SizeIf clinical trials are to influence clinical practice then they must ascertain how big theeffect of the treatment rather than simply stating that the treatment had an effect.Some authors have highlighted the problem that although statistical significance maybe reached between groups or variables, the effect size may not be clinicallysignificant 309;310 . Therefore, as the clinical effect of the EMS devices was consideredan important facet of this study, treatment effect sizes were calculated.Hopkins 311described two methods of producing effect size statistics. Firstly, bycalculating the difference between the mean change over the treatment period withineach group, divided by the SD. This gave a figure that was a fraction of the SD, orrepresented by how many SD the pre and post means differed. An effect size of oneSD was regarded as large, but a figure less than 0.2 SD was regarded as poor andindicated that there was no effect worth considering 311 . A between groups comparisoncould also be calculated to report the change in outcome measures between groupsover the treatment period 308;309 using the same SD values to assess effect.Secondly, another way of reporting effect size statistics was to convert the differenceto a percentage figure. The percentage figure had the advantage of beingdimensionless and more generic 311 . Furthermore, the figure could then be comparedwith the smallest clinically worthwhile effect calculated in the previous reliabilitystudies in Chapter 7.200

___________________________________________________________Chapter 9REFERRED TO TRIALn = 124MISCELLANEOUSn = 17 excludedEXAMINATIONn = 15 excludedGAITn = 12 excludedPRACTICE ASSESSMENTn = 80RANDOMISATIONPatient lostn = 1PRE ASSESSMENT1n = 79START STIMULATIONRESTIM 6 WEEKSn = 38EMPI 6 WEEKSn = 41WITHDRAWNn =1STOP STIMULATIONPOST ASSESSMENTn = 74WITHDRAWNn = 4RESTIMn = 37EMPIn= 37Figure 37 Flow diagram of the protocol of the Main study.The mechanics of the study from the initial referral to the post treatment assessmentafter 6 weeks stimulation.201

___________________________________________________________Chapter 99.5 ResultsOf the 80 patients recruited and consented to enter the trial, six were withdrawn inaccordance with the agreed criteria discussed with the patients (see Appendices).Two of these patients were withdrawn due to device failure. Three did not continuewith the stimulation regime and did not wish to have a post treatment assessment.One patient never attended for post treatment assessment and remained uncontactable.This constitutes a 92% re-attendance rate. This left a remaining studygroup for post treatment analysis of 74 patients. Table 19 and Table 20 providedescriptive statistics of the patients, showing that the groups were well balanced forBMI, male and female distribution, and the tested side, dominant side and affectedside. In terms of age and duration of symptoms, the RESTIM group had a nonsignificant older mean age (P = 0.275). The RESTIM period of 122 weeks for theduration of symptoms is equivalent to 2 years 4 months; the EMPI period of 103weeks is almost exactly 2 years. There was no significant difference between thegroups (p = 0.193).9.5.1 Patient ComplianceUnfortunately, the inbuilt compliance monitors for the RESTIM devices were unable toretain data consistently and correctly and so were deemed unreliable. Therefore allcompliance information was taken from the patients’ self reporting diaries.Non compliance with the treatment programme was defined as missing sevenconsecutive sessions or more than three separate blocks of four sessions. Five202

___________________________________________________________Chapter 9compliance diaries were lost by the patients and never returned. These patients wereincluded in the final analysis because they had a post treatment (week 7)assessment. Data from the 69 patients who completed and returned the diaryrevealed that the mean ±SD number of treatments for each group were 35 (± 6.5) forRESTIM and 35 (± 6.5) for EMPI, differences which were not significant (p =0.915).Figure 38 shows the distribution of the compliance data for both groups. Table 21 is acorrelation matrix for pre treatment outcome measures. There are also correlationmatrices to show no significant associations between treatment compliance and prepostoutcome change (Table 22) and to show no significant associations betweentreatment compliance and any post treatment outcome (Table 23). The influence ofcompliance on the other dependent variables was examined in more detail later bymultiple regression analysis for each of the outcome measures.Figure 38 Distribution of compliance data for RESTIM and EMPI4236number of treatments30241812600 5 10 15 20 25 30 35 40RESTIMnumber of patientsEMPI203

___________________________________________________________Chapter 9Table 19 Descriptive statistics of patients completed (Means ± SD)GROUP N(male : female)BMI AGE(years)Duration ofSymptoms(weeks)RESTIM 37 (16m : 21f) 25.7 ± 5.7 36.5 ± 13.6 122 ± 61EMPI 37 (15m : 22f) 25.9 ± 5.9 33.2 ± 9.4 103 ± 62TOTAL 74 (31m : 43f) 25.8 ± 5.7 35 ± 11.4 112 ± 62Table 20 The distribution of the affected side and leg dominance (Means ± SD)GROUP Dominant side Test side Affected sideRESTIM Left = 1 Left = 16 Left = 11Right = 36 Right = 21 Right = 11EMPI Left = 1Right = 36TOTAL Left = 2Right = 72Left = 18Right = 19Left = 34Right = 40Bilateral = 15Left = 12Right = 14Bilateral = 11Left = 23Right = 25Bilateral = 269.5.2 Pooled groups versus Separate groups.Independent ‘t’ tests showed no significant pre treatment differences (p > 0.05)between the groups for any outcome measure nor for any of the baseline measuresexcept quadriceps CSA. As reported later, there were also no significant posttreatment differences except for quadriceps CSA. Therefore correlation matrices andmultiple regression analyses were justified using the two groups pooled rather thanseparately. Furthermore, when the effect of the independent dichotomous variables204

___________________________________________________________Chapter 9(i.e. gender, treatment group, affected side) on the post treatment variables wereassessed, there were no group effects. This suggested that the theoretical modelwould not be improved by adding ‘group’.9.5.3 Gender effectsIndependent ‘t’ tests revealed that there were no significant differences between maleand female patients for any of the outcome measures (p>0.05). Figure 39 and Figure40 below show the difference in responses to EMS between genders for bothRESTIM and EMPI. Although some experts had anecdotal evidence that EMS wasmore effective in males than females 175 , previous studies had indicated that therewere no greater benefits of EMS for males than females 112 . In contrast, Soo et al. 121found that men displayed greater strength improvements than women (47.7%compared with 8.1%), although their results may be explained by small sample sizesrather than a real sex difference. The only reason proposed in theory for sexdifferences was the greater amount of subcutaneous fat in females. This was notmeasured in the Main study, although the ultrasound scans did reveal a higher CSAmeasure and hence a greater muscle mass for males. The ‘t’ tests to analyse thedichotomous variable of gender were significant for the baseline covariates ofisometric and isokinetic strength and quadriceps CSA. However, when the variablewas included, it did not improve the model. Therefore, it could be concluded that theEMS devices used in this study were no more effective in males than females and theresults of the Main study therefore agree with those of Fahey et al. 112205

___________________________________________________________Chapter 92000RESTIMisometricisokinetic% pre & post differences +- 1 SD150010005000-500-1000quads fatigueVASstepsflexionKujala-1500malefemaleCSAFigure 39 Gender differences in the RESTIM group for all outcome measures2000EMPIisometricisokinetic% pre & post differences +- 1 SD150010005000-500-1000quads fatigueVASstepsflexionKujala-1500malefemaleCSAFigure 40 Gender differences in the EMPI group for all outcome measures206

___________________________________________________________Chapter 99.5.4 CorrelationsTable 21 shows a correlation matrix of the pre treatment variables. Interestingly thisrevealed that of several highly significant associations between baseline outcomemeasures, the tests for muscle physiology, the clinical tests, and the two outcomemeasures of subjective improvement had the highest associations. For example, theassociations between isometric, isokinetic strength and quadriceps CSA were highlysignificant (p < 0.0001). The number of steps and knee flexion were significantlyassociated (p < 0.0001). The Kujala score and the VAS for pain were alsosignificantly associated (p < 0.0001). Table 22 is a correlation matrix produced toexplore any significant associations between treatment compliance and the pre andpost treatment change in outcome measures for all patients. This showed thatcompliance with the stimulation regime was not significantly associated withimprovement in any outcome at all.Table 23 is a correlation matrix produced to examine the associations betweenbaseline measures and the post treatment outcome scores, except quadriceps CSA.This table reveals that the highly significant associations (p< 0.0001) are comparablewith those of the pre treatment associations. There were still highly significantassociations between post treatment isometric, isokinetic strength and quadricepsCSA (p < 0.0001). The number of post treatment steps and knee flexion weresignificantly associated with the additional association of Kujala score (p < 0.0001).The Kujala score and the VAS for pain were still significantly associated, with theaddition of post treatment flexion (p < 0.0001).207

n = 74 age BMI CSA 1 isometric 1 isokinetic 1 quadsfatigue1agePearson’s r.310 -.347 -.372 -.348 .71p Value.007* .002* .001* .002* .531BMIPearson’s rp ValueCSA 1Pearson’s rp Valueisometric 1Pearson’s rp Valueisokinetic 1Pearson’s rp Valuequads fatigue1Pearson’s rp valuepain 1Pearson’s rp Valuesteps 1Pearson’s rp Valueflexion 1Pearson’s rp ValueKujala 1Pearson’s rp Value.310.007*-.347.002*-.372.001*-.348.002*.71.531.019.876-.207.076-.174.137-.143.225.267.021*-.128.278-.250.032*-.181.123-.026.830-.246.034-.383.001*-.245.036*.267.021*.512.0001*-.525.0001*-.128.227.087.463-.024.840-.090.443.113.258-.128.278.512.0001*.800.0001*-.067.568.152.200.016.894.058.625.082.486-.250.032.525.0001*.800.0001*-.124.924-.011.927.052.662.201.086.253.030*-.128.227-.128.227-.067.568-.124.924.092.437.043.715.067.571.180.124pain 1 steps 1 flexion 1 Kujala 1.019.876-.026.830.087.830.152.200-.011.927.092.437-.064.592-.123.301-.496.0001*-.207.076-.246.034*-.024.840.016.894.052.662.043.715-.064.592.548.0001*.252.030*-.174.137-.383.001*-.090.443.058.625.201.086.067.571-.123.301.548.0001*.322.005*-.143.225-.245.036*.113.258.082.486.253.030*.180.124-.496.0001*.252.030*.332.005*

n = 74 age BMI compliance isometric7agePearson’s r.310 -.044 -.378p Value.007* .719 .001*BMIPearson’s rp ValuecompliancePearson’s rp valueisometric 7Pearson’s rp Valueisokinetic 7Pearson’s rp Valuequads fatigue7Pearson’s rp valuepain 7Pearson’s rp Valuesteps 7Pearson’s rp Valueflexion 7Pearson’s rp ValueKujala 7Pearson’s rp ValueCSA 7Pearson’s rp Value.310.007*-.044.719-.378.001*-.381.001*.123.229-.084.476-.140.234-.029.810.028.816-.323.008*-.034.784-.143.225-.185.114-.083.487.079.502-.269.020*-.305.008*-.080.500.272.027*-.034.784.084.491.244.043-.062.615-.039.752.070.570-.066.588.175.149.128.323-.143.225.084.491.814.0001*-.161.173-.070.554.085.469.094.423.088.455.470.0001*isokinetic7-.381.001*-.185.114.244.043*.814.0001*.021.862-.085.471.078.510.090.444.156.184.474.0001*quadsfatigue7.123.299-.083.487-.062.615-.161.173.021.862.064.593-.066.576-.008.944-.069.562-.161.198pain7-.084.476.079.502-.039.752-.070.554-.085.471.064.593-.373.001*-.426.0001*-.761.0001*.248.045*steps7-.140.234-.269.020*.070.570.085.469.078.510-.066.576-.373.001*.675.0001*.556.0001*-.073.558flexion7-.029.810-.305.008*-.066.588.094.423.090.444-.008.944-.426.0001*.675.0001*.483.0001*-.074.555Kujala7.028.816-.080.500.175.149.088.455.156.184-.069.562-.761.0001*.556.0001*.483.0001*-.095.450CSA 7-.323.008*.272.027*.128.323.470.0001*.474.0001*-.1610.98.248.045*-.073.558-.074.555-.095.450

n = 74 compliance isometric c isokinetic c quadsfatigue ccompliancePearson’s r.034 .023 -.071p value.783 .854 .568isometric changePearson’s rp Valueisokinetic changePearson’s rp Valuequads fatiguechangePearson’s rp valuepain changePearson’s rp Valuesteps changePearson’s rp Valueflexion changePearson’s rp ValueKujala changePearson’s rp ValueCSA changePearson’s rp value.034.783.023.854-.071.568-.110.373.074.546-.114.239-.015.900-.152.238.386.001*.357.002*-.233.047*.194.098.275.018*.393.001*.089.476.386.001*.181.127-.089.456-.018.879.049.675.264.023*.007.953.357.002*.181.127.036.768.021.862.080.503.113.266.186.138pain c steps c flexion c Kujala c CSA c-.110.373-.233.047*-.089.456.036.768-.249.034*-.321.006*-.557.0001*-.011.928.074.546.194.098-.018.879.021.862-.249.034*.535.0001*.376.0018-.281.022*-.114.239.275.018*.049.675.080.503-.321.006*.535.0001*.448.0001*-.197.112-.015.900.393.001*.264.023*.113.266-.557.0001*.376.001*.448.0001*-.150.229-.152.238.089.476.007.953186.138-.011.928-.281.022*-.197.112-.150.229

___________________________________________________________Chapter 99.5.5 Isometric Strength9.5.5.1 Pre Treatment AnalysisThere were no statistical differences between the RESTIM and EMPI groups prior totreatment (t = -1.165, P=0.248).9.5.5.2 Post Treatment AnalysisAn independent ‘t’ test showed no significant differences between the groups for posttreatment isometric strength (t = 1.870, p =0.066) (Table 50). Graphicalrepresentation of the pre and post test mean ± SD can be seen below in Figure 41. A2 x 2 ANOVA with one repeated measure revealed a significant time effect (p =0.001), but no significant group effect (p = 0.452). The time by group interaction alsofailed to reach a level of significance (p = 0.066). Nevertheless, in order to facilitatethe discussion a paired ‘t’ test for within group analysis revealed a significantimprovement between pre and post treatment values for RESTIM of 10.5Nm (9.7%)(p =0.0001) but not for EMPI with values of 3.1Nm (2.8%)(p = 0.291). Thus, a 6.9%increase was observed for RESTIM over EMPI (Table 48). The lack of betweengroups statistical significance precluded the calculation of treatment effect sizes.211

___________________________________________________________Chapter 930Difference between pre & post isometric tests20100-10-20N =37RESTIM37EMPIFigure 41 Mean ± SD of pre and post test differences for isometric peak torquefor RESTIM and EMPI. The line at zero = no difference between pre and post values.9.5.5.3 Multiple Regression AnalysisMultiple regression analysis was performed using a theoretical model based on theliterature for PFPS. The following continuous data covariates were used for posttreatment isometric strength: age, treatment compliance, duration of symptoms, pretreatment isometric and isokinetic strength, quadriceps fatigue rate and pain. Inaddition, correlation coefficients were generated from the data to highlight other212

___________________________________________________________Chapter 9variables that might affect the model (Table 24). To assess the effect of thedichotomous variables ‘t’ tests were used(Table 25).Table 24 Association of each continuous baseline covariate and compliancewith Post Treatment Isometric StrengthCO VARIATE Pearson’s r P valueAge 0.378 0.001*Body Mass Index (BMI) -0.143 0.225Duration of symptoms -0.001 0.992Baseline isometric strength 0.900 0.0001*Baseline isokinetic strength 0.818 0.0001*Baseline quadriceps fatigue -0.211 0.070Baseline pain 0.042 0.722Baseline Kujala Score 0.084 0.477Baseline quadriceps cross sectional area (CSA) 0.483 0.0001*Baseline steps 0.033 0.778Baseline knee flexion 0.032 0.784Compliance (number of treatments) 0.084 0.491* = statistically significantTable 25 Association of dichotomous baseline covariate.CO VARIATE t value p valueTreatment group (RESTIM / EMPI) -0.321 0.749Gender (Male / Female) 4.569 0.0001 *Test side (Right / Left) -0.539 0.591* = statistically significant213

___________________________________________________________Chapter 9Of the significant continuous and dichotomous variables discovered in Tables 24 and25 four were already in the model. Two more (i.e. quadriceps CSA and gender) wereduly added to the theoretical model. As described in Chapter 9.4.3.1 a directregressional analysis was performed first to give a R 2 value for the theoretical modelof 0.915, with an adjusted R 2 of 0.813. Next, a stepwise multiple regression revealedthat three pre treatment variables were highly significant predictors of post treatmentisometric strength; these were pre isometric strength, pre isokinetic strength and prefatigue rate measures of the quadriceps. The adjusted R 2 for the third model was0.825, indicating that these three variables could predict 82% of the variability of thepost test isometric values (Table 26). There were no effects from the other variables.The implications are discussed in Chapter 9.6.3.In order to check the fit of the linear regression model, the normality of the residualstatistics were analysed visually by histograms (Figure 42) and scatterplots (Figure43) and tested formally by the Durbin-Watson test. For post treatment isometricmodel, the data were normally distributed with no obvious trends when plotted againstcovariates and each outcome variable. The Durbin – Watson test revealed a statisticof 2.030. The histograms and scatterplots for all other outcome measures may beseen in the appendices.214

___________________________________________________________Chapter 912Isometric strength108Frequency6420Std. Dev = 1.00Mean = .04N = 74.00-2.00-2.25-2.50Regression Standardised Residual2.252.001.751.501.251.00.75.50.250.00-.25-.50-.75-1.00-1.25-1.50-1.75Figure 42 Histogram of normal distribution for isometric strength3Isometric strengthRegression Standardised Residual210-1-2-3-2-1012345Regression Standardised Predicted ValueFigure 43 Scatterplot of residuals for isometric strength215

___________________________________________________________Chapter 9Table 26 Multiple Regression Analysis, Model summaryfor Post Treatment Isometric Strengthmodel 1isometric1model 2isometric1isokinetic1model 3isometric1isokinetic1quads 1R R 2 Adjusted R 2 B t P0.890 0.792 0.7890.969 15.838 0.00010.906 0.820 0.8150.752 8.535 0.00010.242 3.221 0.0020.913 0.833 0.8250.755 8.809 0.0001-53.01 -2.202 0.0030.228 3.103 0.031Legend:- isometric 1 = pre treatment isometric strength.quads 1 = pre treatment quadriceps fatigue.isokinetic 1 = pre treatment isokinetic strength.B = unstandardised coefficient216

___________________________________________________________Chapter 99.5.6 Isokinetic Muscle strength9.5.6.1 Pre Treatment AnalysisThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment ( t = -0.685, p = 0.496).9.5.6.2 Post Treatment AnalysisAn independent ‘t’ test showed no significant differences between the groups for posttreatment isokinetic strength (t = -1.119, p = 0.267) (Table 50). Graphical display ofthe mean ±SD can be seen in Figure 44 below. A 2 x 2 ANOVA with one repeatedmeasure revealed a significant time effect between pre and post treatment measure(p = 0.04) but no significant effect for group (p = 0.355) nor a significant time by groupinteraction (p = 0.267). A paired ‘t’ test revealed significant improvements betweenpre and post treatment values for EMPI of 8.6Nm (7.8%, p =0.008) but not forRESTIM of 3.9Nm (3.7%, p = 0.191). Thus a 4.1% increase was observed for EMPIover RESTIM (Table 49). The lack of between groups statistical significanceprecluded calculation of treatment effect sizes.217

___________________________________________________________Chapter 940Difference between pre & post isokinetic tests3020100-10-20N =36RESTIM37EMPIFigure 44. Mean ± SD of pre and post test differences for isokinetic peak torquefor RESTIM and EMPI. The line at zero = no difference between pre and post values.9.5.6.3 Multiple Regression AnalysisThe theoretical model for post treatment isokinetic strength was applied based on theliterature for PFPS. The following continuous data variables were entered: pretreatment isometric & isokinetic strength, quadriceps fatigue rate, treatmentcompliance, duration of symptoms and pain. Additionally, correlation coefficients weregenerated indicating that there may be other variables that might affect the outcome218

___________________________________________________________Chapter 9(Table 27). To assess the effect of the dichomomous variables ‘t’ tests were used(Table 28).Table 27 Association of each continuous baseline covariates and compliancewith Post Treatment Isokinetic StrengthCO VARIATE Pearson’s r P valueAge -0.381 0.001 *BMI -0.185 0.114Duration of symptoms 0.017 0.886Baseline isometric strength 0.725 0.0001 *Baseline isokinetic strength 0.905 0.0001 *Baseline quadriceps fatigue -0.119 0.312Baseline pain 0.049 0.680Baseline Kujala Score 0.180 0.125Baseline quadriceps CSA 0.498 0.0001 *Baseline steps 0.029 0.808Baseline knee flexion 0.136 0.249Compliance (number of treatments) 0.244 0.043 ** = statistically significantTable 28 Association of dichotomous baseline covariates.CO VARIATE t value p valueTreatment group (RESTIM / EMPI) -1.119 0.267Gender (Male / Female) 4.858 0.0001 *Test side (Right / Left) -1.182 0.241* = statistically significant219

___________________________________________________________Chapter 9Three additional variables were thus added to the theoretical model; gender,quadriceps CSA and age. The process outlined in section 9.4.3.1. was followed. First,a direct regressional analysis was performed to give a theoretical model R 2 value of0.840 and adjusted R 2 of 0.815. Next, a stepwise multiple regression analysisrevealed that only one of the independent variables (pre isokinetic strength) was ahighly significant predictor of post treatment isokinetic strength. The adjusted R 2 forthe model was 0.820, indicating that this variable could predict 82% of the variabilityof the post test isokinetic values (Table 29). There were no effects from the othervariables. In order to check the fit of the linear regression model, the normality of theresidual statistics were analysed visually by histograms and scatterplots (seeappendices) and tested formally by the Durbin-Watson test. For post treatmentisokinetic strength model, the data were normally distributed with no obvious trendswhen plotted against covariates and each outcome variable.Table 29 Multiple Regression Analysis Model Summaryfor Post Treatment Isokinetic Strengthmodel 1isokinetic1R R 2 Adjusted R 2 B t P Durbin -Watson0.907 0.822 0.8200.947 17.479 0.0001 2.037Legend:- isokinetic 1 = pre treatment isokinetic strengthB = unstandardised coefficient Beta220

___________________________________________________________Chapter 99.5.7 Muscle FatigueThe results from the three superficial quadriceps (VMO, VL and RF) were initiallycompared separately and then in combination to provide an overall quadriceps fatigueresult.9.5.7.1 VMOThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment (t = -0.028, p = 0.978). An independent ‘t’ test showed nosignificant differences between the groups for post treatment VMO fatigue rates (t = -0.636, p = 0.527) (Table 49). A graphical representation of group mean ±SD can beseen in Figure 45 below. A 2 x 2 ANOVA with one repeated measure revealed nosignificant effects for time (p = 0.812) nor group (p = 0.527), nor significant time bygroup interaction (p = 0.645). A paired ‘t’ test revealed no significant within groupimprovements in the pre and post treatment slopes neither for RESTIM (p = 0.864)nor for EMPI groups (p = 0.723).221

___________________________________________________________Chapter 9.3Difference between pre & post VMO slopes.2.10.0-.1-.2N =36RESTIM37EMPIFigure 45 Mean ±SD of the pre and post test differences for VMO fatigue slopesfor RESTIM & EMPI. Line at zero = no difference between pre & post test values.9.5.7.2 VLThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment (t = 0.838, p = 0.405). An independent ‘t’ test showed nosignificant differences between the groups for post treatment VL fatigue rates (t = –0.884, p = 0.380 (Table 49). A graphical representation of mean ± SD is in Figure 46below. A 2 x 2 ANOVA with one repeated measure revealed no effects for time (p =0.716 ) nor for group (p = 0.608) and no time by group interaction (p = 0.380). A222

___________________________________________________________Chapter 9paired ‘t’ test revealed no improvements in the pre and post treatment slopes neitherfor RESTIM (p = 0.275) nor for EMPI groups (p = 0.662)..3Difference between pre & post VLat slopes.2.1-.0-.1-.2-.3N =37RESTIM37EMPIFigure 46. Mean ±SD of pre and post differences for VL fatigue slopesfor RESTIM & EMPI. Line at zero = no difference between pre & post test values.223

___________________________________________________________Chapter 99.5.7.3 RFThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment (t = -0.713, p = 0.478). An independent ‘t’ test showed nosignificant differences between the groups for post treatment RF fatigue rates (t =1.139, p =0.258) (Table 49). A graphical representation of the mean ± SD can beseen in Figure 47 below. A 2 x 2 ANOVA with one repeated measure revealed nosignificant effects for time (p = 0.235), nor for group (p = 0.258) nor any time by groupinteractions (p = 0.866). A paired ‘t’ test revealed no improvements in the pre andpost treatment slopes neither for RESTIM (p = 0.678) nor for EMPI groups (p =0.070)..2Difference between pre & post RFem slopes.10.0-.1-.2N =37RESTIM36EMPIFigure 47. Mean ±SD for RF fatigue slope pre and post test differencesFor RESTIM & EMPI. Line at zero = no difference between pre & post test values.224

___________________________________________________________Chapter 99.5.7.4 Quadriceps combinedThe slopes for VMO, VL, and RF were also combined to produce an overallquadriceps fatigue rate. There were no statistically significant differences between theRESTIM and EMPI groups prior to treatment (t = 0.124, p = 0.902). An independent ‘t’test showed no significant differences between the groups for post treatmentquadriceps fatigue rates (t = -0.355, p =0.724) (Table 50). A graphical representationof the group mean ±SD can be seen in Figure 48 below. A 2 x 2 ANOVA with onerepeated measure revealed no significant effects for time (p = 0.532) nor for groups (p= 0.931), nor significant time by group interactions (p = 0.724). A paired ‘t’ test (Table49) revealed no significant improvements in the pre and post treatment slopes neitherfor RESTIM, (-0.001%/s, p = 0.352) nor for EMPI ( -0.003 %/s, p = 0.874)..2Difference between quads slope pre post.10.0-.1-.2N =36RESTIM36EMPIFigure 48. Mean ±SD for combined quadriceps slopesfor RESTIM &EMPILine at zero represents no difference between pre & post test values225

___________________________________________________________Chapter 99.5.7.5 Multiple Regression AnalysisMultiple regression analysis was performed on post treatment combined quadricepsfatigue using a theoretical model based on the literature for PFPS. The followingcontinuous data covariates were used: age, treatment compliance, duration ofsymptoms, pre treatment isometric and isokinetic strength and quadriceps fatiguerate. In addition, correlation coefficients were generated from the data to elucidateother variables that might affect the outcome (Table 30). Dichotomous variables wereanalysed by ‘t’ tests (Table 31).Table 30. Association of each continuous baseline covariate and compliancewith Post Treatment Quadriceps Fatigue RateCO VARIATE Pearson’s r P valueAge 0.123 0.299BMI -0.083 0.487Duration of symptoms -0.075 0.529Baseline isometric strength -0.151 0.181Baseline isokinetic strength -0.040 0.740Baseline quadriceps fatigue 0.478 0.0001 *Baseline pain -0.014 0.905Baseline Kujala Score 0.071 0.550Baseline quadriceps CSA -0.170 0.150Baseline steps 0.098 0.411Baseline knee flexion 0.127 0.285Compliance (number of treatments) -0.062 0.615* = statistically significant226

___________________________________________________________Chapter 9Table 31. Association of dichotomous baseline covariates.CO VARIATE t value p valueTreatment group (RESTIM / EMPI) 0.315 0.754Gender (Male / Female) -0.776 0.440Test side (Right / Left) -0.354 0.724From these analyses no other variables were added to the model. Following theprocedure outlined in section 9.4.3.1., a direct regressional analysis was performed totest the theoretical model, which gave a R 2 value of 0.528 with an adjusted R 2 valueof 0.208. Next, a stepwise regression revealed that the only significant predictor forpost treatment quadriceps fatigue rate was the pre treatment quadriceps fatigue rate(Table 32). The adjusted R 2 for this model was 0.207, indicating that this variablecould only predict 20% of the variability of the post test isometric values. There wereno effects from the other variables. The implications are discussed in section 9.6.4.In order to check the fit of the linear regression model, the normality of the residualstatistics were analysed visually by histograms and scatterplots (see appendices) andtested formally by the Durbin-Watson test.model 1quads 1Table 32 Multiple Regression Analysis Model Summaryfor Post Treatment Quadriceps fatigueR R 2 Adjusted R 2 B T Durbin-0.460 0.212 0.200Watson0.432 4.209 2.024 0.0001PLegend:-quads 1 = quadriceps pre treatment fatigue rateB = unstandardised coefficient227

___________________________________________________________Chapter 99.5.8 Pain9.5.8.1 Pre Treatment AnalysisThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment ( t = 0.448, p = 0.656).9.5.8.2 Post Treatment AnalysisAs the data for this outcome measure were not normally distributed (K-S test p =0.028) further analysis was made using non-parametric tests. A Mann Whitney-U testshowed no significant differences between the groups for post treatment pain levels(Z = -1.153, p = 0.249) (Table 51). A Wilcoxon Signed Ranks test for within groupsanalyses revealed significant pre and post treatment VAS improvements of -1.2 forRESTIM (35%, p = 0.004) and -0.7 for EMPI (20.2%, p = 0.047). Thus a 14.8 %improvement was observed for RESTIM over EMPI (Table 48).A graphical representation of the group medians and interquartile ranges (IQR) canbe seen in Figure 49 below.228

___________________________________________________________Chapter 96Difference between pre & post pain (VAS)420-2-4-6-8N =37RESTIM37EMPIFigure 49. Median and IQR for pre and post test pain differencesfor RESTIM & EMPI.Line at zero = no difference between pre & post test values.N.B. negative values = a decrease in pain.o = outlying values.Due to the non-parametric nature of the data, an exploratory 2 x 2 repeated measuresANOVA was performed. Any findings were then confirmed by using a non-parametricWilcoxon Signed Ranks test. The repeated measures ANOVA revealed a significanteffect for time (p = 0.0001) but not for group (p = 0.915). There were no significanttime x group interactions (p =0.278). The statistical significance for time wasconfirmed by the Wilcoxon Signed Ranks test (RESTIM p = 0.002; EMPI p = 0.034).229

___________________________________________________________Chapter 99.5.8.3 Multiple Regression AnalysisA theoretical model for post treatment pain was applied based on the literature forPFPS. The following continuous data covariates were used: age, treatmentcompliance, duration of symptoms, pre treatment isometric and isokinetic strength. Inaddition, correlation coefficients were generated from the data to investigate othervariables that might affect the outcome (Table 33). Dichotomous variables wereanalysed by ‘t’ tests (Table 34).Table 33 Association of each continuous baseline covariate and compliancewith Post Treatment PainCO VARIATE Pearson’s r P valueAge -0.302 0.069BMI 0.079 0.502Duration of symptoms 0.175 0.302Baseline isometric strength -0.248 0.139Baseline isokinetic strength -0.285 0.087Baseline quadriceps fatigue 0.145 0.218Baseline quadriceps CSA 0.186 0.113Baseline pain 0.458 0.004 *Baseline Kujala Score -0.339 0.040 *Baseline steps -0.146 0.387Baseline knee flexion -0.073 0.669Compliance (number of treatments) -0.088 0.627* = statistically significant230

___________________________________________________________Chapter 9Table 34 Association of dichotomous baseline covariates.CO VARIATE t value p valueTreatment group (RESTIM / EMPI) -0.480 0.632Gender (Male / Female) 1.593 0.115Test side (Right / Left) -0.672 0.504These analyses revealed pre treatment Kujala score to be a significant variable,which was then added to the model. In theory, this finding was expected as the Kujalascore was the other subjective evaluation of the patient’s knee discomfort duringvarious functional activities. A direct regressional analysis was performed asdescribed in section 9.3.4.1. This gave a R 2 value for the theoretical model of 0.555with an adjusted R 2 of 0.227. A stepwise regression revealed that the only significantpredictor for post treatment pain score was the pre treatment pain score. The R 2value for this model was 0.275 with an adjusted R 2of 0.264, indicating that thisvariable could predict 26% of the variability of the post treatment pain values (Table35). There were no effects from the other variables. In order to check the fit of thelinear regression model, the normality of the residual statistics were analysed visuallyby histograms and scatterplots (see appendices) and tested formally by the Durbin-Watson test.model 1Pain 1Table 35 Multiple Regression Analysis Model Summaryfor Post Treatment PainR R 2 Adjusted R 2 B t Durbin-0.525 0.275 0.264Watson0.650 5.007 2.003 0.0001Legend: Pain 1 = pre treatment pain score (VAS) B = unstandardised coefficientP231

___________________________________________________________Chapter 99.5.9 Clinical Tests9.5.9.1 Pre Treatment Analysis - STEPSThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment ( t =-0.057 , p =0.955 ).9.5.9.2 Post Treatment Analysis - STEPSThe number of steps up and steps down were added to give a cumulative posttreatment steps score, whose mean score was 20. As the data were not normallydistributed (K-S test p = 0.019) non-parametric tests were used for post treatmentanalysis. A graphical representation of the group medians and IQR can be seen inFigure 50 below. A Wilcoxon Signed Ranks test revealed significant improvementsbetween pre and post treatment values for RESTIM (6 steps, p = 0.0001) and forEMPI (8 steps, p = 0.0001) (Table 48). A Mann Whitney –U test showed no significantdifferences between the groups for post treatment values (raw difference 3 steps, Z =-0.493, p = 0.562) (Table 51).232

___________________________________________________________Chapter 9120Difference between pre & post treament steps100806040200-20-40N =37RESTIM37EMPIFigure 50. Medians and IQR for pre and post test steps differencesfor RESTIM & EMPI. Line at zero = no difference between pre & post test values.Legend:- o = outlying values. + = extreme valuesDue to the non-parametric nature of the data, an exploratory 2 x 2 ANOVA with onerepeated measure was performed. Any findings were then confirmed by using a nonparametric Wilcoxon Signed Ranks test. The repeated measures ANOVA revealed asignificant effect for time (p =0.0001) but not for group (p = 0.739) nor for time bygroup interactions (p = 0.416). The statistical significance for time was confirmed bythe Wilcoxon Signed Ranks test (RESTIM p = 0.0001; EMPI p = 0.0001).233

___________________________________________________________Chapter 99.5.9.3 Multiple Regression Analysis - STEPSMultiple regression analysis was performed using a theoretical model for posttreatment steps based on the literature for PFPS. The following continuous datacovariates were used: age, treatment compliance, duration of symptoms, pain, pretreatment isometric and isokinetic strength and quadriceps fatigue. In addition,correlation coefficients were generated from the continuous data to discover if therewere other variables that might affect the outcome (Table 36). Dichotomous variableswere analysed by ‘t’ tests (Table 37).Table 36. Association of each continuous baseline covariate and compliancewith Post Treatment StepsCO VARIATE Pearson’s r P valueAge -0.140 0.234BMI -0.269 0.020 *Duration of symptoms -0.033 0.783Baseline isometric strength 0.001 0.996Baseline isokinetic strength 0.108 0.359Baseline quadriceps fatigue -0.114 0.222Baseline quadriceps CSA -0.037 0.751Baseline pain -0.105 0.375Baseline Kujala score 0.310 0.007*Baseline steps 0.632 0.0001*Baseline knee flexion 0.399 0.0001*Compliance (number of treatments) 0.070 0.570* = statistically significant234

___________________________________________________________Chapter 9Table 37. Association of dichotomous baseline covariates.CO VARIATE t value p valueTreatment group (RESTIM / EMPI) 0.611 0.543Gender (Male / Female) -0.407 0.685Test side (Right / Left) -0.743 0.460Knee flexion (the other clinical test) and the Kujala score for functionality weresignificantly associated variables and were added to the model. Furthermore, BMIwas also significantly associated (r = -0.269, p = 0.020), indicating that patients withlower BMI were able to perform more steps (Table 36). Following the procedureoutlined in section 9.4.3.1., a direct multiple regressional analysis was performed totest the theoretical model and generate a R 2 value of 0.696 with an adjusted R 2 of0.384. Next, a stepwise multiple regression revealed that the only significant predictorfor post treatment steps was pre treatment steps. The adjusted R 2 for this model was0.406, indicating that this variable could predict 40% of the variability of the posttreatment steps values (Table 38). There were no effects from the other variables.In order to check the fit of the linear regression model, the normality of the residualstatistics were analysed visually by histograms and scatterplots (see appendices) andtested formally by the Durbin-Watson test. For post treatment steps model, the datawere normally distributed with no obvious trends when plotted against covariates andeach outcome variable.235

___________________________________________________________Chapter 9model 1Steps 1Table 38. Multiple Regression Analysis Model Summaryfor Post Treatment StepsR R 2 Adjusted R 2 B t Durbin-WatsonP0.635 0.403 0.3940.725 6.674 1.820 0.0001Legend:- Steps 1 = pre treatment stepsB = unstandardised coefficient9.5.9.4 Pre Treatment Analysis - FLEXIONThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment (t = 1.076, p = 0.285).9.5.9.5 Post Treatment Analysis - FLEXIONAn independent ‘t’ test showed no significant differences between the groups (t =0.449, p = 0.654) (Table 50). A graphical representation of the mean ±SD can beseen in Figure 51 below. A 2 x 2 ANOVA with one repeated measure revealed asignificant time effect (p = 0.0001) but no significant group effect (p = 0.170) nor timeby group interactions (p = 0.654). A paired ‘t’ test revealed significant improvementsbetween pre and post treatment values of knee flexion for both the RESTIM of 15 0(15%, p = 0.003) and for the EMPI of 12 0 (12.9%, p = 0.0001). Thus a 2.1%improvement was observed for RESTIM over EMPI (Table 48).236

___________________________________________________________Chapter 950Difference between pre post knee flexion403020100-10-20-30N =37RESTIM37EMPIFigure 51. Mean ± SD for pre and post test flexion differencesfor RESTIM & EMPI. Line at zero = no difference between pre & post test values9.5.9.6 Multiple Regression Analysis - FLEXIONMultiple regression analysis was performed using a theoretical model based on theliterature for PFPS. The following covariates were used in the model for posttreatment flexion: pre treatment number of steps, knee flexion, pain, Kujala score,isometric & isokinetic strength, duration of symptoms, age, and treatment compliance.Correlation coefficients were generated to find any other variables that could beadded to the model (Table 39). This table demonstrated highly significant237

___________________________________________________________Chapter 9associations between the clinical tests of steps and flexion and the Kujalafunctionality score. BMI was the only significant variable added to the model.Dichotomous variables were analysed by ‘t’ tests (Table 40).Table 39 Association of each continuous baseline covariate and compliancewith Post Treatment FlexionCO VARIATE Pearson’s r P valueAge -0.029 0.810BMI -0.305 0.008*Duration of symptoms 0.012 0.922Baseline isometric strength 0.017 0.883Baseline isokinetic strength 0.132 0.262Baseline quadriceps fatigue -0.134 0.256Baseline quadriceps CSA -0.101 0.394Baseline pain -0.136 0.250Baseline Kujala score 0.264 0.023*Baseline steps 0.450 0.0001*Baseline knee flexion 0.647 0.0001*Compliance (number of treatments) 0.066 0.588* = statistically significantTable 40 Association of dichotomous baseline covariates.CO VARIATE t value p valueTreatment group (RESTIM / EMPI) 1.429 0.157Gender (Male / Female) 0.332 0.741Test side (Right / Left) -1.643 0.105238

___________________________________________________________Chapter 9A direct multiple regression analysis was performed initially to test the theoreticalmodel. This gave an R 2 value of 0.501 with adjusted R 2 of 0.403. A stepwise multipleregression was then performed to reveal that the only highly significant predictor ofpost treatment knee flexion was pre treatment knee flexion. The adjusted R 2 for themodel was 0.443, indicating that this variable could predict 44% of the variability ofthe post treatment knee flexion (Table 41). There were no effects from the othervariables.In order to check the fit of the linear regression model, the normality of the residualstatistics were analysed visually by histograms and scatterplots (see appendices) andtested formally by the Durbin-Watson test. For post treatment flexion model, the datawere normally distributed with no obvious trends when plotted against covariates andeach outcome variable.model 1flexion1Table 41 Multiple Regression Model Summaryfor Post Treatment FlexionR R 2 Adjusted R 2 B t Durbin-WatsonP0.672 0.451 0.4430.689 7.362 2.032 0.0001Legend:-flexion 1 = baseline flexionB = unstandardised coefficient239

___________________________________________________________Chapter 99.5.10 Kujala Questionnaire9.5.10.1 Pre Treatment AnalysisThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment ( t = 0.970, p =0.335 ).9.5.10.2 Post Treatment AnalysisAn independent ‘t’ test showed no significant differences between the groups for posttreatment Kujala scores (t = -0.772, p = 0.443)(Table 50). A graphical representationof mean ± SD can be seen in Figure 52 below. A 2 x 2 ANOVA with one repeatedmeasure revealed a significant time effect (p = 0.0001) but no group effects (p =0.443) nor time by group interactions (p = 0.502). A paired ‘t’ test revealed significantimprovements between pre and post treatment values for RESTIM (p = 0.007) and forEMPI (p = 0.0001) (Table 48).9.5.10.3 Multiple Regression AnalysisMultiple regression analysis was performed using a theoretical model based on theliterature for PFPS. The following predictor variables were entered in the model: pretreatment isometric and isokinetic strength, pre treatment pain, steps, flexion, Kujalascore, duration of symptoms and compliance. In addition, correlation coefficients weregenerated to illucidate any other covariates that may be used in the model (Table 42).This table shows the significant associations between variables that had already been240

___________________________________________________________Chapter 9entered into the model, viz: the Kujala score for functionality, and pre treatment pain(using the VAS), and the pre treatment clinical tests of flexion and steps.Dichotomous variables were analysed by ‘t’ tests but none were added to the model(Table 43).30Difference between pre post test Kulaja scores20100-10N =37RESTIM37EMPIFigure 52. Mean ± SD for Kujala score pre and post test differencesfor RESTIM & EMPI. Line at zero = no difference between pre & post test values241

___________________________________________________________Chapter 9Table 42 Association of each continuous baseline covariate and compliancewith Post Treatment KujalaCO VARIATE Pearson’s r P valueAge 0.028 0.816BMI -0.080 0.500Duration of symptoms -0.016 0.894Baseline isometric strength -0.052 0.658Baseline isokinetic strength 0.128 0.267Baseline quadriceps fatigue -0.071 0.546Baseline quadriceps CSA -0.022 0.852Baseline pain -0.520 0.0001*Baseline Kujala score 0.673 0.0001*Baseline steps 0.270 0.020*Baseline knee flexion 0.246 0.035*Compliance (number of treatments) 0.175 0.149* = statistically significantTable 43 Association of dichotomous baseline covariates.CO VARIATE t value p valueTreatment group (RESTIM / EMPI) 0.293 0.771Gender (Male / Female) -1.402 0.165Test side (Right / Left) 0.508 0.613As described in section 9.4.3.1., direct regressional analysis was performed to testthe model. This gave a R 2 value of 0.723 with an adjusted R 2 of 0.476. A stepwiseregression analysis was then performed that revealed two variables that were242

___________________________________________________________Chapter 9significant predictors of the post treatment Kujala score: pre treatment pain and pretreatment Kujala score. The adjusted R 2 for the second model was 0.491. Thesevariables therefore accounted for 49% of the variability of the pre treatment Kujalascore (Table 44). There were no other effects from any other variables.In order to check the fit of the linear regression model, the normality of the residualstatistics were analysed visually by histograms and scatterplots (see appendices) andtested formally by the Durbin-Watson test. For post treatment Kujala model, the datawere normally distributed with no obvious trends when plotted against covariates andeach outcome variable.Table 44 Multiple Regression Analysis Model Summaryfor Post Treatment Kujala Scoremodel R R 2 Adjusted R 2 B t Durbin-Watsonmodel 1 0.687 0.472 0.464PKujala10.759 7.686 0.0001model 20.712 0.506 0.491Kujala10.6485.9160.0001Pain 1-1.637-2.121 2.0160.038Legend: Kujala 1 = baseline Kujala acorePain1 = baseline pain score (VAS)B = unstandardised coefficient243

___________________________________________________________Chapter 99.5.11 Quadriceps Cross Sectional Area9.5.11.1 Pre Treatment AnalysisThere were no statistically significant differences between the RESTIM and EMPIgroups prior to treatment (t = -1.198, p = 0.235).9.5.11.2 Post Treatment AnalysisSome patients were unable to have ultrasound scans performed on the poststimulation assessment. Therefore, data from post stimulation scans were taken from33 patients in each group. An independent ‘t’ test showed a significant differencebetween the groups in the post treatment CSA (t = -2.329, p = 0.023) (Table 50). Agraphical representation of mean ± SD can be seen in Figure 53 below. A 2 x 2ANOVA with one repeated measure revealed neither a significant time effect (p =0.225) nor group effect (p = 0.264), but a significant time by group interaction (p =0.023). A paired ‘t’ test revealed significant improvements between pre and posttreatment values for 0.58cm 2 (3.4%) for RESTIM (p = 0.021), but a decrease for EMPIof -0.18cm 2 (0.97%) (p = 0.422) (Table 48).9.5.11.3 Multiple Regression AnalysisMultiple regression was performed using a theoretical model derived from theliterature on PFPS and using the following variables: pre treatment isometric andisokinetic strength, pre treatment quadriceps fatigue, treatment group, compliance,244

___________________________________________________________Chapter 9duration of symptoms, BMI, age, and gender. Correlation coefficients were generatedto highlight any other predictor variables that might be used in the model (Table 45).Dichotomous variables were analysed by ‘t’ tests (Table 46). No other variables wereadded. As outlined in section 9.4.3.1., a direct multiple regressional analysis wasperformed to test the model, which gave an adjusted R 2 value of 0.907 and adjustedR 2 of 0.882.3difference between pre & post treatment CSA210-1-2N =33RESTIM33EMPIFigure 53. Mean ± SD for quadriceps CSA pre and post test differencesfor RESTIM & EMPI. Line at zero = no difference between pre & post test values.245

___________________________________________________________Chapter 9Table 45 Association of each continuous baseline covariate and compliancewith Post Treatment Quadriceps CSACO VARIATE Pearson’s r P valueAge -0.323 0.008*BMI 0.272 0.027*Duration of symptoms -0.020 0.871Baseline isometric strength 0.496 0.0001*Baseline isokinetic strength 0.491 0.0001*Baseline quadriceps fatigue -0.116 0.353Baseline quadriceps CSA 0.952 0.0001*Baseline pain 0.085 0.140Baseline Kujala score 0.075 0.550Baseline steps 0.016 0.900Baseline knee flexion -0.028 0.882Compliance (number of treatments) 0.128 0.323* = statistically significantTable 46 Association of dichotomous baseline covariates.CO VARIATE t value p valueTreatment group (RESTIM / EMPI) -0.761 0.449Gender (Male / Female) 5.845 0.0001*Dominant side (Right / Left) -1.075 0.286Affected side (Right /Left/ Bilateral) 1.072 0.348 †Test side (Right / Left) -0.601 0.550* = statistically significant† = analysed using one way ANOVA246

___________________________________________________________Chapter 9A stepwise multiple regression analysis was next performed to reveal the variable thatbest predicted the post treatment CSA was pre treatment CSA (Table 47). Theadjusted R 2 for this model was 0.883 indicating that 88% of the variance of the posttreatment CSA could be predicted pre treatment CSA. There were no effects on themodel from any other variables.In order to check the fit of the linear regression model, the normality of the residualstatistics were analysed visually by histograms and scatterplots (see appendices) andtested formally by the Durbin-Watson test. For post treatment CSA model, the datawere normally distributed with no obvious trends when plotted against covariates andeach outcome variable.Table 47 Multiple Regression Analysis Model Summaryfor Post treatment Quadriceps CSAmodel R R 2 Adjusted R 2 B t Durbin- PWatsonmodel 1CSA 10.941 0.885 0.8830.941 21.522 2.064 0.0001Legend: CSA 1 = baseline quadriceps cross sectional areaB = unstandardised coefficient247

___________________________________________________________Chapter 99.5.11.4 Treatment Effect SizeEstimates of treatment effect size can be used to determine if the effect of a treatmentis likely to be large enough to be clinically worthwhile. The significant differenceswithin and between the groups after treatment permitted such a calculation for theeffects on quadriceps CSA. The within treatment effect size for RESTIM wascalculated as follows 308;311 :(post CSA X - pre CSA X)--------------------------------------preCSA SD(17.69 – 17.11) (= 0.58)------------------------ ------------4.24 4 .24 = 0.13The figure of 0.13 is below the figure cited by Hopkins (0.24) needed to indicate aworthwhile effect 311 . Therefore the within group statistically significant difference (p =0.021) for RESTIM determined by the ‘t’ tests should be interpreted with caution.248

___________________________________________________________Chapter 9Sometimes it is preferable to report the change or differences in outcome measuresover the treatment period. This was calculated with the following formula 308;311 :(mean change CSA RESTIM – mean change CSA EMPI)_________________________________pooled SD of RESTIM & EMPI (averaged)(+0.58 – -0.181) (= 0.76)------------------------ -------------4.37 4 .37 = 0.17The differences between pre and post CSA values for RESTIM were 0.582 cm 2 . ForEMPI these were -0.181 cm 2 (indicating a decrease in CSA). The SD fraction figure of0.17 is less than the figure of 0.20 cited by Hopkins, indicating that the effect size isvery small and not worth considering. This illustrates the usefulness of calculating theeffect size because the independent ‘t’ test revealed a between group significance (p= 0.023).9.5.12 Gender effects.Analyses were also carried out to assess whether the EMS had a greater effect onmale or female patients. Although some anecdotal evidence has been cited that EMSwas more effective in males than females 175 , previous studies had indicated that therewere no greater benefits of EMS for males than females 112 . In contrast, Soo et al. 121found that men displayed greater strength improvements than women (47.7%249

___________________________________________________________Chapter 9compared with 8.1%), although their results may be explained by small sample sizesrather than a real gender difference. The only reason proposed in theory for genderdifferences was the greater amount of subcutaneous fat in females. This was notmeasured in the Main study, although the ultrasound scans did reveal a higher CSAmeasure and hence a greater muscle mass for males.The ‘t’ tests to analyse the dichotomous variable of gender were significant for thebaseline covariates of isometric and isokinetic strength and quadriceps CSA .However the variable, when added, did not add to the multiple regression model.Therefore, it could be concluded that the EMS devices used in this study were notmore effective in males than females.The following Tables (48, 49, 50 and 51) display the raw data values pre and posttreatment for both groups for all outcome measures. Results are also tabulated forwithin group and between group differences for parametric and non parametric data.250

___________________________________________________________Chapter 9Table 48 Means ± SD or Medians (IQR), pre and post stimulation data.Raw scores and mean percentage changesRESTIMPre-stim Post-stim Mean Change Mean % P value ✝in raw score change frombaselineIsometric strength 107.6 ± 30.8 118.1 ± 37.4 10.5 ± 15.9 9.7% ✝0.0001*(Nm)Isokinetic strength 104.2 ± 35.3 108.1 ± 36.8 3.9 ± 17.6 3.7% ✝0.191(Nm)PAIN (points) 3 (2-5) 2 (0-4) -1(-3 - 0) -33% 0.004*STEPS (No.) 16 (9 -24) 27 (16 -46) 6 (0 -21) 68.7% 0.0001*FLEXION (degrees) 104 ± 27 119 ± 29 15.5 ± 29.4 15% ✝0.003*KUJALA (points) 72 ± 12.9 78 ± 14.6 6 ± 12.1 7.8% ✝0.007*CSA (cm 2 ) 17.11 ± 4.24 17.69 ± 4.29 0.58 ± 1.38 3.3% ✝0.021*EMPIPre-stim Post-stim Mean Change Mean % P value ✝in raw score change frombaselineIsometric strength 117.8 ± 43.5 120.9 ± 39.9 3.1 ± 17.6 2.8% ✝0.291(Nm)Isokinetic strength 110.5 ± 44 119.1 ± 47.7 8.6 ± 18.7 7.8% ✝0.008*(Nm)PAIN (points) 3 (1-4) 2 (1-4) -1(-2 - 0) -33% 0.047*STEPS (No.) 13 (7-60) 28(11-60) 8(0-36) 115% 0.0001*FLEXION (degrees) 97 ± 30 109 ± 29 12 ± 18.5 12.9% ✝0.0001*KUJALA (points) 69.3 ± 14.5 77.1 ± 15 7.8 ± 10.7 11.1% ✝0.001*CSA (cm 2 ) 18.70 ± 4.51 18.52 ± 4.61 -0.18 ± 1.27 -0.97% ✝0.422Legend : * = Statistically significant (P < 0.05)✝ = Paired t test = Wilcoxon ranked signs testNm = Newton metres CSA = Cross sectional AreaTable 49. Quadriceps fatigue data. Means ±SD for normalised slopes251

___________________________________________________________Chapter 9RESTIMPre-stim Post-stim Mean Change in Mean % change P value *raw score from baselineVMO (%/s) -0.085 ± 0.13 -0.094 ± 0.12 -0.009 -10.6 0.740VL (%/s) -0.056 ± 0.08 -0.078 ± 0.09 -0.022 -39.3 0.140RF (%/s) -0.071 ± 0.14 -0.072 ± 0.10 -0.001 -1.41 0.968Quads total (%/s) -0.071 ± 0.07 -0.081 ± 0.09 -0.010 -14.1 0.352EMPIPre-stim Post-stim Mean Change in Mean % change P value *raw score from baselineVMO (%/s) -0.086 ± 0.13 -0.070 ± 0.12 0.016 18.6 0.588VL (%/s) -0.082 ± 0.17 -0.073 ± 0.09 0.009 10.9 0.778RF (%/s) -0.052 ± 0.08 -0.084 ± 0.12 -0.032 -61.5 0.107Quads total (%/s) -0.072 ± -0.08 -0.075 ± 0.08 -0.003 -8.5 0.874Legend: VMO = Vastus Medialis ObliqueVL = Vastus LateralisRF = Rectus FemorisQuads total = VMO/VL/RF combined* = paired t testTable 50. Between group analysis. Independent ‘t’ tests for normalised data252

___________________________________________________________Chapter 9VARIABLE t value p valueIsometric post treatment strength 1.870 0.066Isokinetic post treatment strength -1.119 0.267Quadriceps post treatment fatigue -0.355 0.724Flexion post treatment 0.449 0.654Kujala Score post treatment -0.772 0.443Quadriceps CSA post treatment -2.329 0.023 ** = statistically significantTable 51. Between group analysis. Mann Whitney U tests for non-normalised dataVARIABLE Z value p valuePain post treatment -1.153 0.249Steps post treatment -0.493 0.562Table 52. Power sample calculation from the Main studyOutcomeIsometricIsokineticFatigueObserveddifferencepowerSD 80% 85% 90%7.3 (Nm) 17 83 95 1114.7 (Nm) 18 232 265 3110.01 (%/s) 0.085 516 594 695253

___________________________________________________________Chapter 99.6 DiscussionThis thesis has provided a logical progression from testing outcome measureprotocols then instigating a Pilot study, to conducting a suitably powered, doubleblind, randomised trial comparing the efficacy of two different patterns of EMS on thequadriceps of patients with PFPS. Efficacy was measured using outcome measuresfor muscle strength, fatigue, cross sectional area, knee pain and function. The nullhypothesis for this thesis was that there would be no significant differences betweenthe two EMS protocols. Due to the lack of significant between group differences in allbut one measure, the null hypothesis was accepted.The discussion will address the issues surrounding the baseline data and treatmentcompliance, with the subsequent separate sections discussing the within andbetween group differences for each of the outcome measures. This section will finishwith the limitations of the present study and recommendations for future research.9.6.1 Baseline DataA correlational analysis was performed (Table 21) on pre treatment outcomes in orderto assess if there were any relationships between physical and physiologicalmeasures in the total group of 74 patients with PFPS. Table 21 shows thatrelationships did exist between some of these aspects prior to treatment. There werehighly significant associations at baseline between isometric and isokinetic strength (p= 0.0001), between the clinical tests of knee flexion and steps (p = 0.0001) andbetween the subjective assessments of pain and the Kujala score (p = 0.0001).254

___________________________________________________________Chapter 9These associations provided a useful cross check for the outcome measures ratherthan a formal assessment of concurrent validity, and provided an indication that theywere appropriate for what they proposed to measure. The values for BMI, duration ofPFPS symptoms and the affected side (left, right or bilateral) (Tables 19 & 20) wereconsistent with previous studies on PFPS 212;305;312 . There was a lack of associationbetween duration of symptoms and the other outcome measures that questions thecommon clinical perception that the longer a patient had their PFPS the worse theirstrength, pain and function.The only demographic variable to differ from the literature was the patient’s age. Thereason for this was the variety of age range limitations imposed by other authors. Forexample, Clark et al.’s age limits were 16 -40 years 312 , Natri et al.’s were 15 - 50years 305 , and Yates and Grana were 11-48 years 313 , compared to the Main studycriterion of 18 - 60 years. This contributed to the Main study having a heterogenouspopulation as opposed to a homogenous sample (usually young athletes) that tended,in other studies, to skew parameters such as age and BMI 46 . As mentioned inChapter 2.3. almost all previous demographic data on PFPS arose from sport clinicsor athlete based databases, with a paucity of information from the general population;this thesis has been able redress this imbalance and provide some insight into thisgroup. The lack of an athlete-skewed patient sample has had the advantage of beingmore representative of the typical population of outpatients visiting NHS orthopaedicand physiotherapy clinics. The results are more generalisable to the population ofPFPS at large with consequently less threat to external validity.255

___________________________________________________________Chapter 99.6.2 Treatment CompliancePatient’s compliance with treatment is not commonly considered in the literature onphysiotherapy exercise regimes. Yet with so much emphasis placed on exerciseprogrammes and home treatment protocols, as in the Main study, compliance isnecessary for an appropriate evaluation of patients with patellofemoral disorders 313 .Indeed, decisions concerning the surgical or non-surgical options for PFPS may becompromised without patient co-operation. In a succinct emphasis of this importantissue, Grelsamer and McConnell stated: “Without patient compliance progress is slowor non existent” 50 .The problems associated with the use of patient diaries are well known anddocumented for other knee pathologies such as osteoarthritis 292 . The Main study’scombination of patient’s self reporting compliance diaries and an inbuilt devicecompliance monitor was devised so that one could provide confirmation of the other.Unfortunately unforeseen technical problems ruined this opportunity and all analysiswas based on self reporting diaries.In the Main study, a fully compliant protocol of 42 treatment sessions was onlyachieved by 14 patients overall. This means only 20% of the patient population werefully compliant with the treatment programme. If patients who achieved 41 or 40treatment sessions were also included and described as fully compliant this is stillonly 32%, leaving 68% classified as partially or non-compliant. The mean figure of 35(±6.5) treatment sessions for both groups was therefore less than the full compliancerate. Similarly poor compliance rates by PFPS patients during an active exercise256

___________________________________________________________Chapter 9regime were noted by Yates and Grana 313 and Blond and Hansen 45 . On the otherhand, high compliance rates of at least 90% have been noted studying other kneepathologies such as osteoarthritis using EMS 115 or active exercise 314 and anteriorcruciate ligament repair 179 . These comparisons suggest that the poor compliance ratein the Main study may have been due to patient personality associated with PFPSrather that any difficulty with using EMS as an alternative form of therapeuticexercise.The use of multiple regression analysis including compliance in the model allowedanalysis of all completed patients irrespective of their compliance rate. The resultsshowed that the only post treatment outcome measure affected by patient compliancewas isokinetic strength. Although this had a statistically significant value of p = 0.035,the adjusted R 2was 0.057, indicating that only 5.7% of the variance could beaccounted for by the compliance rate. It is possible to conclude then that thetreatment compliance rate in the Main study had little influence on any of the posttreatment outcome measures.The high non-compliance rate has serious implications for the study’s results. Firstly,it is possible that the different RESTIM and EMPI stimulation patterns were not giventhe opportunity to take effect because patients were not using the devices for longenough. Therefore, the lack of compliance may have affected the predicted outcomesbetween the different stimulation patterns. One of the premises for this thesis was theincorporation of the mixed frequency pattern that included a low frequency (

___________________________________________________________Chapter 9than higher frequencies to induce a change in muscle performance. In other words,the RESTIM low frequency component was never given the opportunity to have itsphysiological effect because it was never used for long enough. Therefore, the lack ofcompliance and the resulting intermittent nature of treatment may not have favouredthis type of adaptation.Secondly, the significant within group improvements may indicate that the patients didnot need to comply fully to achieve a good outcome and raises the question ofwhether the results were in response to treatment or due to a placebo effect. With thelack of a placebo control group in this study (for reasons discussed later in section9.7.) it is not possible to rule out the placebo effect as a reason for the generalimprovement for both groups. Oldham et al. 115compared a patterned mixedfrequency and uniform frequency EMS with a placebo device in osteoarthritic kneepatients. They found that the placebo device caused similar improvements in musclestrength, and in functional tests such as mean velocity of walking and stride lengthcompared to uniform fixed frequency EMS. They attributed this, in part, to the closeinterest taken in the patients, who had been on an 18 months waiting list for kneeoperations, by the treating therapists. The effect of such contact in a group of patientswho had their PFPS condition for an average of 2 years cannot be discounted whenconsidering the results from this study.258

___________________________________________________________Chapter 99.6.3 Changes in Muscle StrengthEMS used in a rehabilitation programme for various knee pathologies has beenthought to minimise 131 , improve 129 or have no effect 130 on quadriceps strength asmeasured by isometric or isokinetic torque. However, Morrissey stated that one of themajor limitations of studying strength changes of the quadriceps after EMS was theeffect of joint pain on the ability of the patient during testing to produce a maximalcontraction 175 . Hsieh et al. 212 noted that 19 from 58 PFPS patients (33%) had ‘testinduced pain’ during OKC isometric tests or OKC isokinetic tests at 60 0 /s. Theyconcluded that OKC isokinetic tests were not totally safe for PFPS patients and thatOKC isometric tests should avoid a maximal quadriceps contraction.Awareness of these problems led to this thesis being the first to thoroughly test CKCisometric and isokinetic methods of assessing lower limb torque and then adopt aCKC protocol to provide an assessment of muscle strength. As fully explained inChapter 4 and Chapter 9.3.2, these CKC testing procedures have been advocated forpatients with PFPS due to a lessening of the patellofemoral joint reaction force andpatellofemoral stress 222 . The fact that no patient either during the reliability testing inChapter 4, during the Pilot study in Chapter 8 or the Main study in this Chaptercomplained of an increase in patellofemoral pain also confirmed the safety of thisprocedure.The isometric and isokinetic tests in the Main study showed evidence that bothRESTIM and EMPI devices could significantly improve muscle strength in patientswith PFPS. RESTIM isometric values improved from 107.6Nm to 118.1Nm (9.7%)259

___________________________________________________________Chapter 9with EMPI improving from 117.8Nm to 120.9Nm (2.8%). Whereas RESTIM isokineticvalues improved from 104.2Nm to 108.1Nm (3.7%) with EMPI improving from110.5Nm to 119.1Nm (7.8%) (Table 48). It is interesting to note that the resultsobtained from isometric assessment were not directly comparable to isokineticassessment. The reasons for this are discussed later in this section.Comparing the absolute torque values with previous PFPS studies that only usedOKC protocols is difficult, as it has been observed recently that lower limb CKCtorque values are lower than the equivalent OKC torque values 315 . Furthermore, thereis a paucity of studies that have observed the effect of EMS on muscle strength inpatients with PFPS. Williams 143 , Johnson et al. 144 and Horodyski and Sharp 145 allfailed to provide raw data and/or adequate statistical analysis to elucidate theobserved substantial strength improvements after using EMS.A more robust study by Werner et al. 30 found modest OKC improvements of 5.9% at60 0 /s and 6.1% at 180 0 /s after 40Hz EMS on PFPS patients that are similar to thosein the Main study that tested in CKC at 90 0 /s.It is difficult to explain why a RESTIM improvement in isometric strength was notcomplimented by an isokinetic improvement, and why the converse was true forEMPI. Nevertheless, several reasons can be proposed for this finding.Firstly, some of the contradictions may be explained by the difference in dynamicsbetween the isometric and isokinetic tests. The ability to activate a muscle maximallyusing a voluntary contraction was assessed using a twitch interpolation technique 140 .For the quadriceps in particular, this technique is of clinical relevance because the260

___________________________________________________________Chapter 9capability of full muscular activation in different knee pathologies including PFPS canbe markedly reduced 241;316 . The twitch interpolation technique was used to overcomecentral fatigue in isometric testing but was not feasible with isokinetic testing.Therefore, it is possible that the isometric tests registered extension torque that wasnearer to a true maximal value because of the exclusion of central fatigue as a factorin muscle performance.Secondly, RESTIM was designed with a ‘doublet’ in the beginning of the pattern(see Figure 31). This was included in light of work, especially on fatigued muscle,which showed that including a ‘doublet’ as part of a constant frequency pattern couldaugment peak force and average force (force/time integral) production 208;317 , whilsthelping to reduce the number of impulses in the stimulation pattern required toproduce this force. For example, the use of a ‘doublet’ as part of RESTIM’s mixedfrequency pattern with a 10 on, 50 off duty cycle, ensured that the number ofimpulses delivered was 90 / min. On the other hand, EMPI with 35 Hz constantfrequency and the same duty cycle delivered 350 impulses / min. This would haveresulted in EMPI patients receiving a greater number of impulses per hour thanRESTIM. If, as believed by some authors, the number of impulses is important inoptimal force generation 96 , then RESTIM would be at a disadvantage and theisokinetic results favouring EMPI may provide a more accurate picture of thechanges.On the other hand, it has recently been found that the ‘doublet’ augments force in amuscle by using the first impulse to take up the slack and stiffen the muscle before261

___________________________________________________________Chapter 9delivering the second impulse 207 . Therefore, assessing the leg with a dynamiccontraction such as isokinetic extension may not have reflected the physiologicalimprovement from the ‘doublet’ as much as isometric assessment at a fixed kneeflexion angle. Indeed, it is now known that a decrease in force augmentation isassociated with delivering ‘doublets’ with dynamic as opposed to isometriccontractions 318 . Therefore, the isometric measurement in this study may have been atruer reflection than the isokinetic of muscle strength improvement.9.6.4 Changes in Muscle FatigueDiscussing the muscle fatigue results in the context of previous studies on thequadriceps is difficult as no other previous studies have assessed this aspect aftertreating PFPS with EMS. All other published studies assessing EMS on PFPS haveused uniform frequencies of 35Hz or higher 30;143-145 and so may not have attempted tomeasure fatigue as, presumably, the authors did not even consider this aspect ofmuscle performance. Oldham et al. 115 produced the only other study so far to analysesimultaneous patterned mixed frequency patterns of EMS on the quadriceps andmeasure fatigue. Using a sustained time to fall to 90% MVIC as a measure ofquadriceps fatigue, they noted that the largest improvement in fatigue resistance wasin the patterned EMS group. These positive results were not reflected in the Mainstudy. The difference in assessing fatigue between the two studies probably explainsthis discrepancy. Quadriceps muscle fatigue was measured in the Main study by theEMG methods recommended by Basmajian and DeLuca 296 and by Roy 297 , in which262

___________________________________________________________Chapter 9the EMG signal is submitted to fast Fourier transformation to obtain a power densityspectrum. The two different approaches cited above measure different aspects of thefatigue process and it is possible that the less sophisticated approach adopted byOldham et al. 115 may have detected differences in the Main study. Conversely, theMain study results may truly reflect the fact that fatigue characteristics remainedunaffected by both stimulation patterns.The rationale for using a mixed frequency pattern of EMS like RESTIM was that anyimprovement in muscle strength, induced by the ‘doublet’ and the high frequencycomponents would not be at the expense of an increase in muscle fatigue, due to thesimultaneous contribution from the low frequency component. In theory, the lowfrequency background component should have been able to preserve and indeedimprove the fatigue characteristics of the muscle thus counterbalancing the other highfrequency components. However, there were no significant pre and post treatmentdifferences in the fatigue slopes between the groups in any of the muscles individuallyor as a combined quadriceps total. There may be several reasons for these findings.Firstly, the background low frequency of 2.5Hz in the RESTIM pattern may bequestionable in light of recent work that has found that the effects of 2.5Hz stimulationwas less profound than using 10Hz stimulation in terms of conversion to type I fatigueresistant phenotypes and contractile speed 194 and enzyme activity 319 . Karba et al. 31also proposed this explanation after their experiments on the human VL muscle. Theirobserved 15% increase in speed of contraction but with unchanged fatigue ratesindicated in their opinion that the VL was undergoing transformation to type IIa fast-263

___________________________________________________________Chapter 9fatigue-resistant muscle rather than wholly to type I or type IIb. It is possible,therefore, that the effect of the 2.5Hz stimulation of the RESTIM on fatigue resistancewas less profound than 10Hz, resulting in no improvement. Secondly, there has beensome controversy amongst experts that, in a complete inversion of the acceptedposition, frequencies close to 35Hz (as in the EMPI) may be beneficial for improvingfatigue rates of muscle (Goldspink, personal communication). Although thiscontroversial explanation has not yet been proven in full experimental circumstances,it may explain the ability of the EMPI to improve strength while preserving fatigueresistance to the same extent as RESTIM.Thirdly, the contradictions between the Main study and animal studies in terms of thephysiological effects on muscle are probably due to the difference in method ofdelivery of EMS to the muscle. Many studies on animals have shown powerful andirrefutable evidence of the effect of EMS on every molecular system of the muscle 96 ,particularly the effect of chronic low frequency EMS on fatigue resistance. Oneimportant feature noted by this study was the contrast between the benefits of EMS inprevious animal species studies and the less impressive results in humans. This hasalso been recognised by other authors in this field 190;320 . Lieber 321 has offered a seriesof reasons for these discrepancies. Firstly, animal studies usually used electrodesthat were surgically implanted whereas almost all human studies usedtranscutaneous stimulation with surface electrodes. Secondly, the use of 24 hourscontinuous stimulation in animals ensured greater doses of stimulation delivered tothe animal muscle. The same amount of stimulation in humans was clinically264

___________________________________________________________Chapter 9unacceptable and almost certainly unfeasible. Thirdly, there were differences in theconditions of stimulation. Human stimulation was usually delivered isometrically bothin the research and clinical setting (as in the Main study), whilst animals were allowedfree movement in the cage during stimulation. This altered the ability of the EMS toattain maximum muscle tension during its delivery to the muscle.Therefore, the setting and delivery to human patients in the Main study were probablyinsufficient to allow the low frequency EMS to take effect. When this is coupled withpoor treatment compliance, then it is possible that the amount of low frequencystimulation the quadriceps received was insufficient for RESTIM to have an effecttowards a greater adaptation to resist fatigue.9.6.5 Changes in PainThe statistically significant within group improvements for RESTIM (p = 0.004, 35%)and EMPI (p = 0.047, 20.6%) appear impressive (Table 48), yet there were nostatistically significant differences between the groups (p>0.05) (Table 51).Furthermore, the raw data from the VAS reveals an improvement (i.e. a decrease inscore) of -1.2 for RESTIM and -0.7 for EMPI, allowing the percentage improvementsto exaggerate the raw improvements. As there are no subdivisions between integerson the 10cm VAS, the accepted practice is to ‘round off’ numbers to the nearestinteger. Following this practice, the figures of -1.2 and -0.7 can be rounded off to -1for both RESTIM and EMPI i.e. the same decrease in pain for both groups. There is265

___________________________________________________________Chapter 9no opinion as to how clinically important a change of one point is on a visual analoguescale and this one point difference may be clinically meaningless.Comparison with previous studies was hampered by differences in methods used toassess pain. For example, the lack of between group significance was similar to theOldham et al 115comparison of different patterns of EMS for the quadriceps onosteoarthritic knees, but pain was assessed solely by a component of the NottinghamHealth Profile. Gould et al. 158 found an EMS group to be significantly superior to acontrol group (P < 0.01) over a two weeks period, but they assessed acute pain reliefpost menisectomy by monitoring analgesic medication requirements. Haug andWood 181 also noted a decrease in analgesia medication post knee arthroplasty and a“sense of pain relief” in their EMS group who also received continuous passivemotion. The closest patient group to the Main study was the ‘chondromalacia patellae’group in the uncontrolled study by Johnson et al 144 . Here too there was a decrease inpain ranging from 60% for the mildly affected group to 84% in the severely affectedgroup, but the method of pain measurement was not described.A reduction in patellofemoral pain accompanying an improvement in knee functionhas been previously noted 322 . A common explanation for pain relief is that animprovement in quadriceps strength provides stability of the patella resuming normalpatellar tracking during knee extension and flexion thus resulting in pain reduction 222 .Optimising patellar position has been cited as an important factor in significantlyreducing patellar symptoms. The correction to normal function and movement putsless stress on the pain sensitive patellar retinaculum and other peripatellar tissues266

___________________________________________________________Chapter 9with a resulting improvement in knee stability 50 . The Main study provided somesupporting evidence for this theory. Not only were there improvements in pain andmuscle strength, but there were also correlations between the pre to post treatmentchange in the VAS and those in flexion, steps, the Kujala score and isometric strength(Table 21).Using EMS provides a method of improving patellofemoral pain via an improvementin muscle function, particularly when inhibition hinders exercise and efficient voluntarymotor activation 323 . Yet since 1979, Eriksson and Haggmark 147broached thepossibility that some of the positive effects on the quadriceps muscle from theiranterior cruciate ligament case study could have resulted purely from pain reliefacquired directly from the EMS device. Since then other studies have discussed thispossibility in both acute and chronic knee pathologies 131;158 . Morrissey’s review 175implied that EMS could bring about pain relief either from a correction of quadricepsmuscle imbalance or by blocking pain signals as the EMS offered an alternativesensory stimulus via the pain gate theory. It is possible, therefore, that the frequencyof the RESTIM and EMPI stimulation currents could have provided pain relief viaperipheral and central mechanisms similar to transcutaneous electrical nervestimulation (TENS) or interferential current. Both stimulators operated at frequenciessimilar to TENS and the improvement in strength and function could have resulted inpain relief facilitating muscle contraction rather than a result of improved musclestrength per se.267

___________________________________________________________Chapter 9However, some authors have suggested that TENS and interferential therapy onlyhave an analgesic effect when the patients receive the stimulation and this rapidlydissipates when the treatment session stops 324;325 . As all patients in the Main studywere assessed at least several hours after completing the treatment programme itseems more likely that the pain improvement was due to a carry over effect from theEMS rather than a TENS effect. Therefore, the less transient pain relief was probablydue to improved strength and function. This may be the reason that all previousstudies involving EMS on PFPS that have noted an improvement in function ormuscle strength or pain relief have not entertained the possibility of a TENS effect.Despite this, a recent review on EMS, albeit on osteoarthritis of the knee, recognisesthat this aspect warrants further investigation 326 .9.6.6 Changes in Clinical TestsClinical tests were included to assess the effect of EMS on knee function. The stepsand flexion tests replicated the typical signs and symptoms reported by patients withPFPS such as pain on ascending and descending stairs, squatting and prolongedsitting. McConnell 89stated that these tests form part of a dynamic evaluation ofmuscle action, symptomology and treatment effectiveness and advocated them forpatellofemoral joint evaluation. Similar tests have been used in recent studies ofPFPS by Witvrouw et al. 284 who noted that two different exercise regimes improvedasymptomatic knee flexion and the number of asymptomatic steps. In the Main study,the strong correlation (r = 0.675, p = 0.0001) between post treatment flexion and post268

___________________________________________________________Chapter 9treatment steps provided some concurrent validity to the tests and indicated that onlyone of these functional outcome measures may be needed in future studies.9.6.6.1 StepsSeveral studies have used ascending and descending steps as a measure offunctional activity when investigating PFPS 10;72;327 . Only one previous study alsoassessed a step up and step down to assess a treatment regime 284 . Witvrouw et al. 284had similar results to the Main study in that both step up and step down tests showedsignificant within group improvements over a 5 week training period, but no betweengroup differences. They attributed this to an association between strength, functionand pain. The 68.7% improvement for RESTIM and 115% for EMPI were highlysignificant (p < 0.0001). This improvement could be explained by correspondingimprovements in strength and pain as both these factors would ease the step up anddown activity considerably. The patient would then feel more able to perform the taskbecause either they felt stronger or they felt less pain. Evidence from the Main studypointed to the latter as there was a correlation between post treatment steps anddecreased pain (r = -0.373, p = 0.001), but no association with increased strength. Itis difficult to explain why a greater than 68% increase in the step test wasaccompanied by a less than 10% increase in isokinetic and isometric musclestrength, especially when other authors stated clearly the importance of musclestrength for function. An explanation may lie in a careful analysis of Witrouw et al’sresults 284 . These revealed that CKC testing at 60 0 /s only resulted in between a 5 –269

___________________________________________________________Chapter 910% strength increase, with at least 100% improvement in steps. In other words, theytoo had a functional increase far in excess of a strength increase. It is likely that in theMain study an accompanying 33% improvement in pain may have had a moreprofound effect than the 10% gain in muscle strength. Strength, it seems, was lessrelevant than pain in improving the steps test.9.6.6.2 FlexionThe mean range of motion for the knee prior to treatment was 104 0 for RESTIM and97 0 for EMPI with both improving to 119 0 and 109 0 respectively (Table 48). Theseranges were less than the excepted standard range of motion of 135 0 with the caveatthat the standard measurement was calculated with the subjects in supine 328 . TheMain study used a weight bearing knee flexion assessment as this is more functionaland relevant test for patients with PFPS 230 . The difference in testing positions wouldexplain discrepancies in the pre treatment figures of 100 0 recorded for 79 patients inthis study and those of 137 0 noted for 99 runners with anterior knee pain tested insupine 8 . The Main study showed a significant knee flexion improvement within bothgroups that in theory could be due to a concomitant improvement in pain, or musclestrength. The patient may have felt less discomfort on knee flexion or felt strongerand began to use the knee better in functional everyday circumstances, resulting ingreater range of motion and better stretch of the quadriceps and other knee tissues.The results showed strong correlations between pain score and flexion, but not with270

___________________________________________________________Chapter 9strength indicating that (as with the increase in steps) the increase in flexion is likelyto be explained by a decrease in pain rather than increase in strength.In the clinical setting exercises to increase flexibility of the knee tissues and thequadriceps are regularly prescribed. This was not done in the Main study for tworeasons. Firstly, adding a second exercise regime to the EMS programme may haveproved too time consuming, complicated and even unacceptable for some patients.Secondly, the introduction of a stretching regime to the quadriceps would have hadimportant physiological implications to the study. Animal studies have indicated thatthere may be some use in adding passive stretching to an EMS regime 146 . If passivestretch could possibly have influenced the outcome, then it was important to eliminatethis as a confounding variable in this study. Nevertheless, the concept of combiningpassive stretch and EMS remains an important consideration for future studies.9.6.7 Changes in Kujala questionnaireThe improvement in Kujala score had high within groups statistical significance(RESTIM: 6 points, 7.8%, p = 0.007; EMPI: 7.8 points, 11.1% p = 0.001) (Table 48),but no between groups differences (Table 50). The raw difference of 1.8 pointsbetween the groups is unlikely to be clinically significant, unlike the largerimprovements seen within groups. The concomitant improvements in musclestrength, pain, steps, knee flexion and Kujala score for both groups was not surprisingas the Kujala score has been used in previous studies on PFPS as a representationof ‘functionality’ 281 . Indeed the improvements between pre and post treatment Kujala271

___________________________________________________________Chapter 9score were significantly associated with improvements in isokinetic and isometricstrength, steps, flexion and pain.In theory the improved muscle performance would have provided patellar stability andprobably helped the patient to perform better many of the functional tasks describedin the questionnaire such as stair climbing and descending, prolonged walking, liftingand squatting. Similarly, an improvement in pain recorded by the VAS was reflectedin the questions about generalised pain at night, day or during any activities 283;284 .Witvrouw et al. 284 recorded similar Kujala results in their comparison of OKC and CKCexercise groups, with significant within group but no between group differences. Theyalso noted the ‘important’ associations between muscle strength increases,improvement in functionality and a decrease in pain.9.6.8 Changes in Quadriceps Cross Sectional AreaThis was the only outcome measure that revealed a significant difference betweenthe RESTIM and EMPI groups. This was contrary to the Pilot study results, in Chapter8, and to a previous study that had used patterned EMS on patients with osteoarthritisof the knee 292 . The different results between the study by Howe 292 and this study mayhave been due to slight differences in scanning techniques. The difference from thePilot study is probably due to a smaller sample size causing a statistical type ll error.Singer 323 used CT scans pre and post high frequency EMS on the quadriceps of 15males with a variety of unspecified knee conditions and found a mean non-significantimprovement of 2.72% (p > 0.05). However, this was accompanied by a significant272

___________________________________________________________Chapter 922% improvement (p< 0.001) in mean force production of the quadriceps. Hehypothesised then 323 and discussed in a later paper 329 that EMS could improveneuromuscular efficiency (as seen in the increase in force) rather than have ahypertrophic influence (as seen in the unchanged quadriceps CSA). The concept ofneural adaptation during EMS to explain strength changes in the absence ofmorphological changes in the muscle has also been discussed previously 330 .Only one other study has used an acceptable method of measuring quadriceps CSAbefore and after treating PFPS with EMS. Werner et al. 30 used CT scanning andalthough they described a 6% improvement of the VMO relative to the VL after 40Hzstimulation the raw data and statistics were not presented, nor an explanation howthey managed to distinguish the VMO from the vastus medialis in their calculations.Differences in CSA between RESTIM and EMPI in the Main study could have beendue to variations in treatment time or the amount of muscle targetted by each EMSregime. However, data from the compliance diaries indicated that there were nodifferences between the groups in the number of treatments applied (RESTIM = 35 ±6.5 : EMPI 35 ± 6.5) and the multiple regressional analysis confirmed that compliancewas not a predictor variable. Furthermore, in order to standardise the muscularcontraction during treatment, all patients were instructed to set the amplitude of eachdevice to the highest possible for a strong, yet comfortable contraction. This wasestimated after pre pilot work on healthy subjects to be about 20% of a maximumvoluntary isometric contraction irrespective of the EMS device used. This is close tothe 25% of MVIC attained by Lieber and Kelly 190 .273

___________________________________________________________Chapter 9The statistically significant result between the groups may be interpreted as RESTIMhaving an effect on muscle size that was clinically worthwhile. RESTIM CSAincreased by 0.582cm 2 , whereas EMPI CSA decreased by 0.181 cm 2 . However,caution should be exercised when interpreting these results. In Chapter 7.4.1 theSDD for quadriceps CSA was calculated as 0.80cm 2 , which is the value neededbefore declaring that there was a worthwhile change in CSA. Therefore, althoughthere is a statistically significant difference between the RESTIM and EMPI regimes,(p = 0.023) and within RESTIM (p = 0.021) these figures are smaller than themeasurement error incurred when using an ultrasound scanning technique. As suchthe results may simply be due to limitations in the measurement technique.9.7 Limitations of and recommendations from the studyThe major limitation that should be considered for this Main study was the lack of acontrol group. This limitation has also been acknowledged in previous studiescomparing two or more types of EMS (after ACL repair) 142;179 or exercise programmeson PFPS patients 284;331 . Witvrouw et al. 284 , for example, performed a randomisedprospective study of two exercise regimes on PFPS. They did not use a control groupfor two reasons. Firstly, it was considered unethical to withhold treatment from thesepatients. Secondly, due to the chronicity of the patients’ condition (mean duration 65weeks) they believed it was improbable that any significant natural improvementwould have occurred during the timescale of the study. They were, therefore,“relatively certain” that the significant improvements resulted from the exercise274

___________________________________________________________Chapter 9programmes. A similar rationale had been used earlier by Thomeé 331 . He believedtime was not a major reason for patient’s improvement based on the observation thatthe patients had received no treatment without relief of symptoms for an average of32 weeks prior to his study. In the Main study, the mean duration in the patients’condition prior to treatment was even longer at 112 weeks for both groups combined.Furthermore, patients were referred from the clinical settings of orthopaedic clinicsand general practice and so there were ethical considerations when withholdingtreatment from a patient who was referred for treatment, albeit in a researchenvironment. One alternative would have been to use the patients contralateral limbas an internal control. However, other researchers in the field of EMS have advisedagainst this method due to the possibility of a bilateral training affect of the EMSillustrating the phenomenon of cross transfer within the nervous system affecting bothmotoneurone pools 323 .All other aspects of the trial were controlled as rigorously as possible by adopting thegold standard RCT approach, ensuring that it was adequately powered and thevalidity and reliability of the outcome measures involved. Furthermore, theheterogenous nature of the patient sample supports the external validity of the trialresults. The results were, therefore, considered valid and should be interpreted assuch.275

___________________________________________________________Chapter 99.8 ConclusionThis thesis has attempted a logical progression of demonstrating reliable outcometesting, then conducting a Pilot study prior to instigating a well powered, robust andrigorous double blinded, randomised trial.The aim was to compare the effect of a mixed frequency pattern of EMS containing adoublet, high and a low frequency components with a uniform pattern containing afixed frequency of 35Hz using a commercially available EMS device.After successfully conducting reliability studies and a Pilot study, the Main studydeveloped the protocol further with 80 patients. This showed that delivering asimultaneous mixed frequency pattern of EMS or a uniform frequency EMS pattern tothe human quadriceps resulted in similar outcomes for patients with PFPS.The results, therefore, did not permit the rejection of the null hypothesis.It would appear that the effects of both types of stimulation are similar, being no betternor worse than any other documented approach to this clinical problem. Finding amore effective evidence based approach to treatment remains a challenge to allhealth professionals involved in the management of patients with this condition.276

___________________________________________________________Chapter 99.9 Thesis OverviewAn overview of the thesis allows further analysis and discussion of the problems thatmay have impacted on the results of the Main study. It is only by highlighting theseissues now that studies on EMS and PFPS can be helped and guided in the future.9.9.1 Inclusion and Exclusion CriteriaAll patients in the Pilot study and the Main study referred from either orthopaedic orrheumatology clinics were having been diagnosed with PFPS. It is commonly written(and therefore commonly accepted) that the aetiology of PFPS is ‘multifactorial’. Thisis stated in this thesis in section 2.3. What is less clear from texts using thisdescription is whether the patients are multifactorial or unifactorial. In other words,although the condition is multifactorial the patients may only have one of theaetiological features of this condition. The cause of the patellar problem can be dueto one major factor, but the problem itself can vary from patient to patient. Thepremise behind the clinical examination and gait analysis was to ensure that patientswhose condition could be attributed, for example, to abnormal foot and anklepronation or tightness of the hamstring muscles or referred pain from the lumbarspine or hip joint were not treated with a quadriceps strengthening programme ofEMS when the source of the problem was arising from an identifiable causeelsewhere in the body. From the results in Chapters 4 and 5 (that support the strongevidence from the literature) patients with PFPS exhibited weakened quadricepsmuscles and the absence of any abnormal clinical finding means that the patients277

___________________________________________________________Chapter 9were being treated appropriately with a EMS muscle strengthening regime for thecause of their PFPS. Care should be taken to ensure that patients with multifactorialaetiology are properly screened to enable an appropriate rehabilitation regime to takeplace. Screening methods need not be expensive, and a thorough examination by anexperienced clinician is sufficient to ensure that patients with unifactorial pathology,such as quadriceps weakness, are treated with the appropriate regime.9.9.2 Sample SizeThe sample size for the Main study was calculated from the Pilot study data of 14patients. Despite using the same clinical condition, diagnosed in the same clinics, thesame outcome measures, and the same treatment modality (albeit with a differentcomparative control EMS device as stated in section 8.10) the Main study wasconsiderably underpowered (see Table 52). Reasons for this may be that the Pilotstudy had a patient sample with 2 males and 12 females. As it is well documentedthat females exhibit weaker quadriceps than males, the Pilot study values forquadriceps isometric and isokinetic strength were lower than the Main study. Forexample, the mean isometric pre treatment value in the Pilot study was 66.2Nm, butwas 107Nm in the Main study. It is likely that the disparity in gender distribution hadan effect on the power calculation for the Main study. Therefore, care should be takenthat data taken from pilot studies preceding larger trials to perform power calculationsare performed on a similar gender mix anticipated in the larger study. A pilot study is278

___________________________________________________________Chapter 9often prone to rapid recruitment in an understandable attempt to gather informationquickly and this thesis has elucidated the problem of an imbalanced mix of gender.9.9.3 AutocorrelationMultiple regression models were introduced into the Main study to check for variablessuch as compliance which may have had an effect on the other variables. However,there are some limitations to using modelling in this way that concern autocorrelationor co-linearity. In this study many of the co-variates were highly correlated with eachother as observed in the correlation matrices (Table 21). For example isometricstrength and isokinetic strength could be said to have an inbuilt correlation becausethey are performing a very similar evaluation i.e. quadriceps muscle strength.Unfortunately, if two highly correlated co-variates are in a model, then it is difficult todetect both effects independently and it is possible to pick up a variable because iscorrelated rather than because it is causal. Also, there is a chance that one of themwill be missed because it is being masked by its autocorrelated covariate. Therefore,the model may not be the theoretically or causally correct one.These problems are described as ‘co-linearity’ or ‘autocorrelation’ and are based onthe same phenomenon. In this study, histograms and scatterplots were created andanalysed and a Durbin-Watson statistic produced to evaluate the possibility of nonnormallydistributed data. Therefore, researchers of future studies that perform similaroutcome measures should be aware of these limitations of multiple regressionmodelling and the methods to check for their existence.279

___________________________________________________________Chapter 99.9.4 ComplianceAs with all pragmatic clinical trials, and indeed all aspects of physiotherapyrehabilitation, compliance of the patient is extremely important. Full compliance withthe treatment programme was only achieved by a minority although this was spreadevenly between the two groups. The reasons for this lack of compliance are not easyto explain. Compared to other home treatment based programmes, the Main studyprotocol was not complex and in many ways represented a ‘best-case-scenario’ forhome treatment i.e. it was applied in lying or sitting and the device controlled allstimulation parameters except intensity. It is possible that applying treatmenteveryday was problematic for some patients and that a programme of stimulation onalternate days may in future lead to improved compliance. Due to the instructionsgiven to the patients at the outset of treatment, it was presumed that they used thehighest comfortable intensity of stimulation over the treatment period. However, dueto the software failures already reported in Chapter 9, the output intensity could notbe monitored. Consequently, it is possible that some patients found even the lowerlevels of current output uncomfortable with the result that their quadriceps contractionwas minor with a minimal effect on the muscle. It is therefore imperative that newerversions of EMS devices have some form of reliable inbuilt compliance monitor sothat these important aspects can be evaluated correctly with proper data.280

___________________________________________________________Chapter 99.9.5 Reasons for No Differences between GroupsDespite patients in both groups improving in almost every outcome measure, thecurrent investigation reported in this thesis found no differences between the twogroups except for quadriceps CSA, which could be deemed clinically insignificant.The reasons for this may be explained to some extent by the issues cited in theparagraphs above. Sample size and patient compliance are difficult aspects of anyclinical trial when patient volunteer recruitment is achieved in a clinical setting andother aspects of a patient’s condition may affect their ability to comply with treatment.If these aspects are not taken into account then it may be erroneously concluded thatthere were no differences between groups. Nevertheless, pragmatic clinical trials forman important aspect of physiotherapy research and it behoves the researcher to beboth aware and wary of the problems encountered by and highlighted in this thesis.281

_________________________________________________________ReferencesREFERENCES282

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__________________________________________________________ReferencesAPPENDICES312

__________________________________________________________Appendices11 APPENDICESCONSENT FORMVERSION 02:Issue date 22/10/99Centre for Rehabilitation Science, Manchester Royal Infirmary Oxford Road M13 9WLProject Number: CT97/13Title of project: Evaluation of a new electrotherapyFor quadriceps rehabilitation in patients with patellofemoral pain syndrome (PFPS)Name of investigators: Mr M.J.CallaghanProf. J.A. OldhamPatient identification number for this trial:1. I confirm that I have read and understand the information sheetdated 22/10/99 version 2 for the above trial and have had theopportunity to ask questions.please initial boxes:2. I understand that my participation is voluntary and I am free towithdraw at any time without giving any reason, without mymedical care or legal rights being affected.3. I understand that sections of any of my medical notes may beLooked at by responsible individuals at Smith & Nephew or fromRegulatory authorities where it is relevant to my taking part inresearch. I give permission for these individuals to have accessto my records.4. I agree to take part in the above trial.5. I agree to my GP being told of my taking part in this study (delete): yes no______________________ __________ __________________Name of patient (print) Date Signature________________________ ___________ ____________________Investigator (print) Date Signature____________________ _ ___________ ____________________Name of person taking consent Date Signature If not investigator (print)313

__________________________________________________________AppendicesCENTRE FOR REHABILITATION SCIENCEMANCHESTER ROYAL INFIRMARYOXFORD ROADMANCHESTER M13 9WLEnglandEVALUATION OF A NEW ELECTROTHERAPY FOR QUADRICEPSREHABILITATION IN PATIENTS WITH PATELLOFEMORAL PAIN SYNDROMEPATIENT INFORMATION SHEET Version 2(Issue date 22/10/99)Please read carefully and feel free to ask us for some more information or explainsomething you do not understand.Aims of the studyWe would like you to consider taking part in a research study to look at the best formof electrotherapy treatment for your knee condition.Methods of the studyTreatment will involve electrical stimulation of the thigh muscle in your affected leg.You will be randomly assigned to one of the following groups that will each receive adifferent pattern of stimulation.New pattern of stimulation.Conventional pattern of stimulationOnce assigned to one of these groups you will take a muscle stimulator home and willhave to use it for up to one hour every day for six weeks as instructed. During thisone hour stimulation you will need to sit down and read the paper or watch television.You leg will feel tingly and will 'jiggle' up and down at regular intervals. This is anunusual sensation and it may be difficult to walk whilst receiving treatment. We willask you to keep a diary of your compliance with the stimulation.314

__________________________________________________________AppendicesIn addition everyone participating in the trial will take part in a number ofassessments. These will be undertaken on a number of separate occasions. 3assessments will be made before you receive treatment that will be approximatelyone week apart. After 6 weeks of treatment, you will be assessed again to look forimprovements in your condition. This may be followed by another assessment 3months later. All of these assessments will take place at the Centre for RehabilitationScience, Manchester Royal Infirmary.We will be assessing the following on each of these occasions:The strength and stamina of your thigh muscles.Any pain you may be experiencing in your knee joint.Your ability to climb stairs and squat.We will also ask you a few questions about your knee in general.In addition at the initial assessment, the beginning and end of the six weeksstimulation period and three months (if appropriate) after the stimulation period we willneed to take an ultrasound scan of your thigh to assess the size of the muscle. Thistechnique is the same as that used for scanning babies in the womb. You will receivea specific appointment time calling you in for these tests.All of these tests are very safe and will be explained and demonstrated to you beforeyou have a go.Effects/Benefits from participating in the studyElectrical Muscle Stimulators (EMS) are used to relax muscle spasm, prevent musclewastage, increase local blood flow and to maintain or increase a patient's range ofmotion. In a small number of cases patients have experienced skin irritation andburns beneath the electrodes when using EMS devices. Although these irritations canusually be reduced by moving the electrodes it is vital that you inform Mr MichaelCallaghan, Professor Jackie Oldham or Clare Depledge immediately if youexperience any of these effects. If you have any worries or questions about takingpart in this study after reading these please do not hesitate to ask us for help or moreinformation.We can only guess what the effect stimulation of your thigh muscle will have.315

__________________________________________________________AppendicesRespect of confidentialityAny information you give us and any results we collect from you will be keptconfidential. Our records will refer to you as a number rather than your nameso no one can link your results to you. Anything you tell us will be treated with thestrictest confidence.Reimbursement for participating in the studyWe will make sure you are not out of pocket by participating in the trial and will refundany of your travelling expenses.Your rightsThe decision to take part in this study is up to you and you can change your mindabout taking part without giving a reason at any time without affecting your case andtreatment in the future. We are also happy to discuss any queries at any stage of thetrial.Our rightsWe retain the right to withdraw you from the trial at any point if we think it appropriateto do so.Contact Names, Addresses and Telephone Numbers:Michael Callaghan, Prof. Jackie Oldham or Clare DepledgeCentre for Rehabilitation ScienceManchester Royal Infirmary Oxford RoadManchester M13 9WLTel: 0161-276-6672316

__________________________________________________________AppendicesKUJALA PFPS SCOREFor each question circle the letter which corresponds to your most recent kneesymptoms1. LIMPA None 5B Slight or periodical 3C Constant 02. SUPPORTA Full support without pain 5B Painful 3C Weight bearing impossible 03. WALKINGA Unlimited 5B More than 1 1 / 2 miles 3C Up to 1 mile 2D Unable to do 04. STAIRSA No difficulty 10B Slight pain when going down 8C Pain on going up and down 5D Unable to do 05. SQUATTINGA No difficulty 5B Repeated squatting painful 4C Painful each time 3D Possible with partial weight bearing 2E Unable to do 07. JUMPINGA No difficulty 10B Slight difficulty 7C Constant pain 2D Unable to do 0317

__________________________________________________________Appendices8. PROLONGED SITTING WITH KNEES BENTA No difficulty 10B Pain after exercise 8C Constant pain 6D Pain forces knees to straighten temporarily 4E Unable to do 09. PAINA None 10B Slight and occasional 8C Interferes with sleep 6D Occasionally severe 3E Constant and severe 010. SWELLINGA None 10B After severe exertion 8C After daily activities 6D Every evening 4E Constant 011. ABNORMAL PAINFUL KNEECAP MOVEMENTSA None 10B Occasionally in sports activities 8C Occasionally in daily activities 6D At least one documented dislocation 4E More than 2 dislocations 012. ATROPHY OF THE THIGHA None 5B Slight 3C Severe 013. FLEXION DEFICIENCYA None 5B Slight 3C Severe 0Total Score: / 100Adapted from Kujala et al. Scoring of patellofemoral disorders.Arthroscopy 1993;9(2):159-163318

__________________________________________________________AppendicesTypical graph of patient with normal gait parameters included in Main study319

__________________________________________________________AppendicesRaw data of the graph on previous page320

__________________________________________________________AppendicesTypical graph of a patient excluded due to abnormal gait parameters.321

__________________________________________________________AppendicesRaw data of excluded patient on previous page322

__________________________________________________________AppendicesHISTOGRAMS AND SCATTERPLOTS OF OUTCOME MEASURES(Isometric strength on page 215)20Isokinetic strengthFrequency10Std. Dev = 1.08Mean = .060N = 74.00-2.50 -1.50 -.50-2.00 -1.00 0.00.501.50 2.50 3.501.00 2.00 3.00Regression Standardised Residual4Isokinetic strengthRegression Standardised Residual3210-1-2-3-3-2-101234Regression Standardised Predicted Value323

__________________________________________________________Appendices12Quadriceps fatigue10864Frequency202.502.252.001.751.501.251.00.75.50.250.00-.25-.50-.75-1.00-1.25-1.50-1.75-2.00-2.25Std. Dev = .98Mean = .02N = 73.00Regression Standardized Residual3Quadriceps fatigueRegression Standardised Residual210-1-2-3-4-3-2-10123Regression Standardised Predicted Value324

__________________________________________________________Appendices20PainFrequency10Std. Dev = .97Mean = .030N = 73.00-2.00-1.50-1.00-.500.00.501.001.502.002.50Regression Standardised Residual3PainRegression Standardised Residual210-1-2-3-2-101234Regression Standardised Predicted Value325

__________________________________________________________Appendices12Steps108Frequency642Std. Dev = 1.00Mean = .010N = 74.00-2.00 -1.50 -1.00 -.50 0.00 .50 1.00 1.50 2.00-1.75 -1.25 -.75 -.25 .25 .75 1.25 1.75Regression Standardised Residual3StepsRegression Standardised Residual210-1-2-3-3-2-10123Regression Standardised Predicted Value326

__________________________________________________________Appendices30Flexion20Frequency10Std. Dev = 1.00Mean = .010N = 74.00-3.00 -2.00 -1.00-2.50 -1.50-.500.00.501.001.502.00Regression Standardised Residual3FlexionRegression Standardised Residual210-1-2-3-3-2-10123Regression Standardised Predicted Value327

__________________________________________________________Appendices12Kujala Questionnaire108Frequency6420Std. Dev = .96Mean = -.02N = 73.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75Regression Standardised Residual21.751.501.251.00.75.50.250.00-.25-.50-.75-1.00Kujala QuestionnaireRegression Standardised Residual10-1-2-3-3-2-1012Regression Standardised Predicted Value328