Thursday-Abstracts

Official Journal of the American College of Sports Medicine
landing (0.31 J/BW/ BH) both increased mechanical work compared to regular landing
(0.28 J/BW/ BH, p< 0.001). CONCLUSION: Landing with increased knee flexion
landing and soft landing both decreased ACL loading, but also decreased movement
speed and jump height while increasing mechanical work indicating a decrease in
performance. Simply instructing individuals to land with increased knee flexion or land
softly might have limited application in athletic competition because of the decrease
in performance. Long-term training may be necessary to modify movements without
compromising performance.
1023 May 30, 8:15 AM - 8:30 AM
aCL Injury alters Pre-injury Coordination Of The hip and
Knee: The JuMP aCL study
Benjamin M. Goerger 1 , Stephen W. Marshall 2 , Anthony I.
Beutler 3 , J. Troy Blackburn 2 , John H. Wilckens 4 , Darin A.
Padua 2 . 1 George Mason University, Manassas, VA. 2 The
University of North Carolina at Chapel Hill, Chapel Hill,
NC. 3 Uniformed Services University of the Health Sciences,
Bethesda, MD. 4 Johns Hopkins University, Baltimore, MD.
(No relationships reported)
Those with anterior cruciate ligament (ACL) injury and reconstruction (ACLR) display
movement coordination that may predispose them to subsequent ACL injury and
osteoarthritis. There is limited evidence regarding whether these factors are induced by
ACLR or existed prior to injury.
PurPOsE: The purpose of this study was to compare joint coordination prior to and
following ACL injury and reconstruction in both the injured and noninjured limb.
METhOds: Sixty-nine participants of the JUMP ACL study, a multi-year prospective
study conducted at the United States service academies to identify risk factors for
noncontact ACL injury, completed testing for this analysis, 31 that suffered an ACL
injury (Cases), and 38 that did not. Because unilateral biomechanics were collected
during initial testing the Cases were further divided into those that injured the tested
limb (ACLR-INJ: n = 12 (8 m, 4 f), Age = 21.42 ± 0.79 years, Height = 174.29 ± 7.56
cm, Mass = 76.25 ± 9.95 kg) and those that injured the non-tested limb (ACLR-NINJ:
n = 19 (9 m, 10 f), Age = 21.47 ± 0.77 years, Height = 170.05 ± 9.13 cm, Mass = 72.87
± 12.78 kg). Participants that never suffered an ACL injury (CON: n = 38 (19 m, 19 f),
Age = 20.95 ± 0.73 years, Height = 172.16 ± 8.71 cm, Mass = 72.35 ± 12.37 kg) were
matched based on cohort year, academy and gender. Average coupling angles during
a double leg jump landing between the hip and knee were calculated using a vector
coding technique prior to (Baseline) and following ACL injury and ACLR (Follow-
Up). A 2x3 (Time: Baseline, Follow-Up; Group: ACLR-INJ, ACLR-NINJ, CON)
mixed model ANCOVA (Gender) was performed for each dependent variable.
rEsuLTs: We observed a significant change in the average coupling angle of the hip
and knee in the transverse plane for the ALCR-INJ group (F(2,65)=4.40, p = 0.016).
The change indicated the ACLR-INJ group had more equal relative motion between
the hip and knee in the transverse plane following ACL injury and ACLR (Baseline:
54.85 ± 6.96; Follow-Up: 47.97 ± 6.64).
CONCLusION: Based on our observations, it appears ACL injury and/or ACLR
caused altered coordination of hip and knee rotation, possibly due to decreased
independence of knee rotation. Our findings may provide important insights into the
specific dysfunction underlying the increased risk of recurrent ACL injury in those
with prior ACL injury.
1024 May 30, 8:30 AM - 8:45 AM
adaptation Of Quadriceps and hamstring Co-contraction
Following Landing Instruction In Patients With acl
reconstruction
Audrey RC Elias, Curt D. Hammill, Ryan L. Mizner. University
of Montana, Missoula, MT.
(No relationships reported)
A growing body of evidence suggests the ACL reconstructed knee exhibits
compromised ability to accept weight and attenuate force during high demand
activities, which can be mitigated with instruction and training. Controversy exists
surrounding the desired agonist-antagonist relationship of the hamstrings and
quadriceps in landing tasks, particularly in ACL injury prevention and end-stage ACLR
rehabilitation programs.
PurPOsE: To explore adaptations in neuromuscular control of the quadriceps and
hamstrings to instruction for improved knee performance during weight acceptance.
METhOds: Thirty physically active subjects with unilateral ACLR and good clinical
results participated in a one-time session analyzing single leg landing of the involved
limb off a 20 cm platform using 3-D motion analysis system with force plates.
Vertical ground reaction force (VGRF) and peak knee flexion served as measures of
performance. Vastus lateralis and biceps femoris recruitment were analyzed using
surface EMG and normalized to maximal voluntary isometric contraction(MVIC).
Testing was repeated after 5 minutes of instruction in desired landing patterns.
Hamstring/quadriceps co-contraction indices were integrated over the weight
acceptance phase of landing, and results were analyzed with paired t-tests.
rEsuLTs: Landing performance improved with training, with increased peak knee
Vol. 45 No. 5 Supplement S185
flexion (mean±SD; pre: 55±11°; post: 78±11°; p