Clinical Assessment of Trunk Flexor Muscle Strength in Healthy Girls ...

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Clinical Assessment of Trunk Flexor Muscle Strength in Healthy Girls 3 to 7 Years of Age KAREN L. BALDAUF, DIANE K. SWENSON, JOHN M. MEDEIROS, and SANDRA A. RADTKA We developed a clinical method for assessing trunk flexor muscle strength in healthy children that can be applied to assist physical therapists in determining strength accurately in pediatric patients. In this study, we assessed trunk flexor muscle strength in 75 healthy girls 3 to 7 years of age. Muscle strength was graded on a scale of 0 to 5 using modified, manual muscle testing methods. These methods attempted to minimize the amount of hip flexor muscle activity during trunk flexion and allow more isolated action of the abdominal trunk flexor muscles. The frequency of Normal (Grade 5) strength first appeared to predominate at age 5 years with the majority of children demonstrating Normal (Grade 5) strength by age 7 years. Regression analysis illustrated a positive linear relationship (β = .37, p < .001) between mean muscle grade and age group. We discuss muscle cross-sectional area, muscle-fiber diameter, muscle-cell number, maturation of the central nervous system, and changes in body proportions with age as possible contributing factors to the results of this study. Key Words: Abdomen, Child development, Muscles, Physical therapy. Current clinical methods of assessing muscular strength in children are not standardized and are often highly subjective. The physical therapist measuring strength in children may do so by observing functional activities such as reaching, rolling, or coming to stance. The child may be asked to perform a specific movement or to maintain a position to test the strength of specific muscle groups. Grades for adult manual muscle tests are often used as the norm when testing trunk flexor muscle strength in children. This study presents a clinically feasible method for assessing trunk flexor muscle strength in children by using testing procedures appropriate to a child's level of ability. Various manual muscle testing methods have been used to assess adult abdominal strength clinically. Kendall et al have proposed two different procedures to measure abdominal muscle strength. 1 One method assesses a person's ability to keep the lumbar spine flat against the table while lowering both legs, with knees extended, from an initial position of 90 degrees of hip flexion. The point in the range of motion at which the lumbar spine begins to demonstrate lordosis determines the muscle grade. Their second method assesses strength based on the ability to flex the vertebral column and come to a sitting position while the legs remain stabilized in Ms. Baldauf and Ms. Swenson were Master of Arts candidates when this research was completed at the Division of Physical Therapy, Stanford University School of Medicine, Stanford, CA 94305. Ms. Baldauf is now Staff Physical Therapist, Veteran's Administration Hospital, Palo Alto, CA 94304 (USA). Ms. Swenson is now a physical therapist at California Children's Services, Alameda County, CA 94607. Dr. Medeiros is Acting Director and Assistant Professor, Division of Physical Therapy, Stanford University School of Medicine, Stanford, CA 94305. Ms. Radtka is a doctoral candidate, School of Education, University of California, Berkeley, CA 94720. This article was submitted June 27, 1983; was with the authors for revision 22 weeks; and was accepted March 1,1984. extension. Daniels and Worthingham assign grades of trunk flexor muscle strength by having the person clear the scapulae from the table during trunk flexion. 2 The lower extremities are stabilized in extension during their Normal (Grade 5), Good (Grade 4), and Fair (Grade 3) muscle test positions. Harvey and Scott attempted to measure abdominal muscle strength in young women using a timed curl-up (reverse situp) test. 3 Adult abdominal muscle strength has been quantitatively measured in the supine position using a dynamometer 4 and the Cybex ® II* isokinetic dynamometer system. 5 Adult trunk flexor muscle strength has similarly been assessed using the Cybex ® II dynamometer. 6.7 A protocol has recently been developed for testing trunk flexor strength in the upright position using the Cybex ® II system. 8 Numerous electromyographic (EMG) studies have attempted to determine the positions in which the abdominal muscles are the most active. Such information is useful in maximizing abdominal muscle activity during strength testing. Flint has established that rectus abdominus muscle activity is greatest in the early stages of trunk flexion and decreases as the iliacus muscle becomes more active when the trunk is flexed past 45 degrees. 9,10 Halpern and Bleck compared the duration of abdominal muscle activity in various sit-up positions. 11 They found initial trunk flexion through partial range (scapular clearance) elicited the greatest duration of abdominal muscle activity. The position of hip and knee flexion has been shown to increase the amount of EMG activity from the rectus abdominus muscle 12, l3 (pp30l-309) and to decrease the activity of the rectus femoris muscles. 14 Eliminating stabilization to the lower extremities during trunk flexion has also been shown to increase the activity of the rectus abdominus * Cybex, Div of Lumex, Inc, 2100 Smithtown Ave, Ronkonkoma, NY 11779. Volume 64 / Number 8, August 1984 1203 Downloaded from http://ptjournal.apta.org/ by guest on March 25, 2013
muscle 10 and to decrease rectus femoris muscle activity. 12,14,l5 The decrease in activity of the hip flexor muscles during situps with hip and knee flexion and without stabilization is generally attributed to the shortened position of these muscles. 13 (pp301-309), 15 Girardin states, "The reduction in distance between the origin and insertion of the hip flexors and the psoas has most probably decreased their participation and therefore enhanced the rectus abdominus involvement. " 13(p307) Measures of normal strength in children have focused largely on physical fitness tests. The American Association for Health, Physical Education, and Recreation in 1956 assessed abdominal muscle strength in children by having them flex and rotate the trunk while the lower extremities were supported in an extended position. 16 Children throughout the United States were assigned percentile grades (as measures of abdominal strength) according to the maximum number of sit-ups they could complete. The revised 1975 version of the sit-up test measured the number of sit-ups a child could perform in one minute. 17 In this procedure, the hips and knees were flexed, feet were supported, and the trunk rotation requirement was eliminated. Percentile normative data for these tests were computed throughout the United States for 500 children who were 7 through 15 years of age. Glover, using the same sit-up procedure with a 30-second time limit, established norms of abdominal muscle strength for primary grade children. 18 Flint and Diehl attempted to quantify abdominal strength in children using a cable tensiometer to measure the force of trunk flexion. 19 Sit-ups with knees flexed and feet stabilized were performed for this measurement. Sit-ups performed through full range of trunk flexion may cause or contribute to degenerative changes in the lumbar disks. 8 The stress placed on the lumbar spine is decreased with trunk flexion through partial range of motion. 20 Therefore, sit-ups performed through partial range may be an effective method of measuring abdominal muscle strength while protecting the lumbar spine. A position that maximizes the action of the abdominal muscles during trunk flexion must be developed to assess abdominal muscle function. Electromyographic research and biomechanical principles have provided the basis for modifying current trunk flexor muscle test positions. The purpose of this study is to assess clinically trunk flexor muscle strength in girls 3 to 7 years of age using a method based on results of EMG and biomechanical investigations. METHOD Subjects Using a sample of convenience, we selected 80 girls 3 to 7 years of age to participate in this study. All subjects were healthy girls residing in the San Francisco Bay area who met the following inclusion criteria: 1) no history of hip or trunk surgery reported by parents and 2) ability to perform neck flexion in the supine position through full range of motion. Two subjects were excluded because of past surgeries. Two 3year-old subjects and one 4-year-old subject were excluded because of their inability to perform neck flexion through full range of motion against gravity. The remaining 75 children were divided into five groups according to exact chronological age in years with 15 girls in each age group. The researchers recorded height, weight, and birthdate for each child. We obtained parental consent forms for each subject before the subjects participated in this study. Equipment We constructed an adjustable thigh stabilization board to support each child's hips in 90 degrees of flexion during the test procedure. The lower legs rested over the top of the board in approximately 120 degrees of knee flexion. We supplied the subjects with a floor exercise mat for comfort. Test Design and Grading We placed the subjects in a supine position on the mat in a modified sit-up position with hips flexed to 90 degrees and knees flexed approximately 120 degrees across the top of the board. We chose this position to maximize the activity of the abdominal trunk flexor muscles and minimize the activity of the hip flexor muscles. We assigned numerical values.to muscle grades (Normal, Grade 5; Good, Grade 4; Fair, Grade 3; Poor, Grade 2; Trace, Grade 1; and Zero, Grade 0). The vertebral spinous process at the level of the inferior angle of the scapulae was marked with an adhesive circle, 0.5 in (1.27 cm) in diameter. The criterion for passing the muscle test in the Normal, Good, and Fair positions was the subject's ability to lift the marked vertebra completely from the mat so that the vertebra was visible to one examiner seated on the floor about 2 ft (0.61 m) behind the child. We adapted upper extremity positions for each muscle test from the trunk flexor muscle testing method of Daniels and Worthingham. 2 For a Normal muscle test grade, the child's hands were clasped behind the neck and arms were adducted over the ears during trunk flexion (Fig. 1). In the Good muscle test position, arms were folded across the chest (Fig. 2). Arms were extended with approximately 90 degrees of shoulder flexion in the Fair muscle test position (Fig. 3). A Poor muscle test grade was assigned if the subject could not pass the Fair muscle test but could flex the cervical spine and partially lift the scapulae from the mat (Fig. 4). A Trace muscle test grade was assigned if the subject could not pass the Poor muscle test but could contract the abdominal muscles during coughing, exhaling, or attempting to flex the Fig. 1. Normal (Grade 5) muscle test position. 1204 PHYSICAL THERAPY Downloaded from http://ptjournal.apta.org/ by guest on March 25, 2013
Page 1: Clinical Assessment of Trunk Flexor
Page 5 and 6: TABLE 1 Means and Standard Deviatio
Page 7 and 8: contribution of these muscles durin

Clinical Assessment of Trunk Flexor Muscle Strength in Healthy Girls ...

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