Hip-Abductor Muscle Performance in Participants After 45 Seconds of Resisted Sidestepping Using an Elastic Band

Transcription

1 J Sport Rehabil. 2006,15, Human Kinetics, Inc. ORIGINAL RESEARCH REPORTS Hip-Abductor Muscle Performance in Participants After 45 Seconds of Resisted Sidestepping Using an Elastic Band James W. Youdas, Erica F. Loder, Jody L. Moldenhauer, Christine R. Paulsen, and John H. Hollman Context: Hip-abductor weakness is associated with many lower extremity injuries. A simple procedure to assess hip-abductor performance is necessary in patient populations. Objective: To describe the change in pelvic-on-femoral position of the stance limb before and after 45 seconds of resisted sidestepping. Design: Crosssectional comparative. Setting: Laboratory. Participants: 24 healthy women (24.6 ± 3.5 years) and 14 healthy men (24.5 ± 3.0 years). Main Outcome Measures: Pelvic-on-femoral position in degrees in single-leg stance before and after 45 seconds of resisted sidestepping. Results: The difference between the baseline and postexercise measurements for both men and women was significant (P <.05). The effect of the resisted-sidestepping exercise on the hip abductors was not statistically different between men and women. Conclusions: Forty-five seconds of resisted sidestepping using an elastic band produced a change in pelvic-on-femoral position in healthy adults. This test might be useful to detect impaired performance in hip abductors of patients with injury elsewhere in the musculoskeletal system. Key Words: elastic-band resistance, gluteus medius, Trendelenburg test The function of the gluteus medius, gluteus minimus, and tensor fasciae latae muscles, collectively known as the hip-abductor muscles, is well known. These muscles control pelvic-on-femoral motion in the frontal plane during weight-bearing activities. 1,2 During the single-limb-stance portion of the gait cycle, body mass creates an external moment (by definition, moment = F d) around an anteroposterior axis that passes through the center of the weight-bearing femoral head. This external moment or demand causes the pelvis to adduct, or tilt inferiorly, approximately 5 in the frontal plane relative to the femur of the stance side. 3,4 In response, a net internalabduction moment is created via activation of the hip abductors. Specifically, during the first 20% of the stance phase, the hip abductors contract eccentrically, allowing the contralateral pelvis to tilt in the frontal plane. Subsequently, between 20% and 60% of the gait cycle, the hip abductors reverse their action and contract concentrically to elevate the contralateral pelvis. 3 Youdas and Hollman are with the Mayo Clinic College of Medicine, Rochester, MN Loder is with Providence Portland Medical Center, Portland, OR Moldenhauer is with Bismarck Chiropractice Clinic, 1033 Basin Avenue, Bismarck, ND Paulsen is with United Medical Center, 213 East 23rd St, Cheyenne, WY Youdas(1) 1 1/17/06, 10:40:06 AM

2 2 Youdas et al Investigators have described several musculoskeletal impairments related to weakness of the hip abductors Altered muscle performance of the hip abductors has been associated with injury to the low back, knee, and ankle foot complex. Hip-abductor muscle weakness can have a major influence on alignment of the thigh and leg in the frontal plane during routine daily activities such as climbing or descending stairs and sitting or squatting. 11 In addition, patients could be impaired by malalignment of the thigh and leg when landing from a jump. 12 Numerous investigators have measured the performance of the hip abductors with the traditional manual muscle test (MMT) using a handheld dynamometer (HHD), including examiner- and belt-resisted techniques, 13 tensiometers, 14 special torque tables, 15 and an isokinetic dynamometer. 16 These joint-specific methods typically require the subject to perform femoral-on-pelvic motion in a non-weightbearing position. Grading scales range from ordinal for the MMT to ratio for the HHD and isokinetic dynamometer. Critics of the MMT argue that it is joint specific and overestimates a patientʼs muscle performance. 17 Although dynamometers provide ratio data, they require meticulous stabilization procedures. Furthermore, all these techniques challenge the hip abductors in a non-weight-bearing position, which is different from the way the muscles are used during walking or running. Trendelenburg originally described a functional test for the hip abductors. 18 This test lacked an operational definition, however, so examiners often were unclear regarding how the test should be interpreted. Hardcastle and Nade 2 described a standard procedure for performing and interpreting the Trendelenburg test. The examiner stands behind the patient and observes the angle formed between the line joining the iliac crests and the ground. The patient is asked to flex the hip and knee on the side not being tested so the foot is clear of the ground. The position of the pelvis is noted. Once balanced, the patient raises the nonstance lower extremity as high as possible while keeping the trunk vertical. A nominal scale was used to measure the performance of hip abductors. A normal grade was assigned if the standing posture could be maintained for 30 seconds. The performance was classified as abnormal if the pelvis could be elevated on the nonstance side but the subject failed to maintain the elevated pelvic position for 30 seconds. By measuring the pelvic-on-femoral position of the stance hip during the Trendelenburg test with a universal handheld goniometer using landmarks routinely palpated by clinicians, the performance of the hip abductors in standing could be recorded using a ratio level of measurement. Because the hip abductors provide pelvic stabilization in the frontal plane during weight-bearing activities, it would seem appropriate to select a technique clinicians could use to assess hip-abductor performance in this position without needing costly instrumentation systems. By measuring pelvic-on-femoral position (stance-side hip adduction) before and after a brief period of challenging dynamic hip-abduction exercise, clinicians could assess the muscle performance of a patientʼs hip abductors. Therefore, the purpose of our study was to describe the change in the pelvic-on-femoral position of the stance limb as measured with the Trendelenburg test after a brief period of hip-abductor exercise. We hypothesized that a healthy subject would demonstrate a statistically significant increase in pelvic-on-femoral hip adduction using the Trendelenburg test after the hip abductors of the stance limb were challenged by a 45-second exercise bout of sidestepping using an elastic 01Youdas(1) 2 1/17/06, 10:40:09 AM

3 Hip-Abductor Muscle Performance 3 band. Furthermore, we also hypothesized that women would demonstrate a greater change in pelvic-on-femoral hip adduction than their male counterparts. Subjects Methods The characteristics of the subjects in the study are summarized in Table 1. To be included in the study, volunteers had to meet the following criteria: (1) no current or previous hip-joint lesion, (2) normal passive and active range of motion of both hip joints, (3) normal results of an MMT of the hip abductors, 19 (4) negative FABERE test results, 20 (5) negative Stinchfield test results, 20 and (6) no evidence of lower extremity dysfunction as assessed by visual observation of gait on level surfaces. This study was approved by the Mayo Foundation Institutional Review Board, and each subject signed an approved consent form. Materials A universal goniometer with a double-armed full-circle protractor made of transparent plastic (Fred Sammons, Inc, Burr Ridge, Ill) was used to measure the pelvic-on-femoral position of the stance-leg hip joint. The length of the arms was 31.3 cm (12.25 in), and the scale of the protractor was marked in 1 increments. We chose the goniometer because it is commonly used by clinicians to measure joint mobility. An elastic SPRI band (Donovan Industries Inc, Tampa, Fla) 2.54 cm wide and cm long was used to provide resistance to sidestepping movements of the lower extremities. Two elastic SPRI bands were used in the study and were alternated between subjects. Each band was tested and loaded using standard procedures before being used in the study. The loading and unloading curves for the elastic band are shown in Figure 1. Youngʼs modulus of elasticity was calculated to be 2.2 ± 0.2 N/cm. Procedures Subjects were asked to kick a soccer ball with their preferred lower extremity. This lower extremity was then considered the dominant one. The nondominant leg was used as the stance leg during the measurement of pelvic-on-femoral position. Table 1 Descriptive Characteristics of the Subjects * Characteristic Women (n = 28) Men (n = 14) Age, y 24.6 ± 3.5 (22 39) 24.5 ± 3.0 (20 31)0 Height, m 1.7 ± 0.1 ( ) 1.8 ± 0.1 ( )0 Body mass, kg 62.8 ± 12.1 ( ) 86.5 ± 16.7 ( ) *Values are mean ± SD (range). 01Youdas(1) 3 1/17/06, 10:40:11 AM

4 4 Youdas et al Figure 1 Load (N) versus deformation (% resting length) of the elastic bands. Each data point represents the average of 27 readings (3 measurements from each of 9 different bands). All subjects wore shorts (men) or shorts and a sports bra (women) for adequate exposure of the trunk, pelvis, and thigh. Each subject stood, looking forward, with the arms hanging loosely at the sides and the trunk and craniocervical spine erect. One investigator palpated both right and left anterior superior iliac spines (ASISs) and marked their locations with a pen. The subject was instructed to assume singlelimb stance on the nondominant lower extremity by flexing the opposite hip to about 45, with neutral hip rotation, so the foot cleared the ground. Trunk position was tightly controlled. Subjects were instructed to keep the trunk vertical and not to lean toward or away from the weight-bearing extremity. This position was closely monitored by one of the investigators. The subject maintained this position for 15 seconds. Next, the examiner aligned the goniometer according to the marks on the ilium. The axis of the masked goniometer was centered over the ASIS on the nondominant side. The stationary arm was aligned with the anterior midline of the nondominant femur, using the midline of the patella as a reference, and the moveable arm was aligned with an imaginary straight line connecting the right and left ASISs. After each measurement, the examiner handed the masked goniometer to the recorder, who recorded the measured value and returned the goniometer to the examiner with the arms folded and the device reading 0. The skin marks were not removed before the second measurement. A second measurement of pelvic-onfemoral adduction was made immediately without the subject altering the singleleg-stance posture. This procedure was first performed on 10 volunteers to assess the intratester reliability for the measurement of pelvic-on-femoral motion in the frontal plane. These individuals were not among the 42 subjects studied before and after the elastic-band exercise. 01Youdas(1) 4 1/17/06, 10:40:12 AM

5 Hip-Abductor Muscle Performance 5 Because the measurement of pelvic-on-femoral position demonstrated intratester reliability, only 1 measurement of pelvic-on-femoral position was made at baseline and after 45 seconds of resisted exercise to the hip abductors for the 42 volunteers. The examiner did not use a masked goniometer but instead read the measurement scale and reported the result to the recorder. After baseline pelvic-on-femoral position had been measured, the subject was instructed to perform a series of sidesteps for 45 seconds against resistance provided by an elastic SPRI band. The subject assumed a crouched position with the hips and knees flexed and the lumbar spine in a neutral position. The elastic band encircled the legs just proximal to the lateral malleoli and became taut as the subjectʼs feet moved to shoulder width (Figure 2). On command, the subject began a series of repetitive sidesteps along a corridor 30 m in length. The hip of the dominant LE (a) (b) (c) Figure 2 The resisted-sidestepping exercise using an elastic band. (a) The band is placed around both legs just proximal to the malleoli. The subject positions the feet at shoulder width. (b) The exercise begins when the dominant right lower extremity is abducted, creating increased tension in the band. The nondominant left lower extremity remains stationary until the dominant lower extremity becomes weight bearing. (c) The subject voluntarily lifts the left foot from the floor and allows the hip to adduct by eccentric action of the left hip-abductor muscles. This process is repeated for 45 seconds. 01Youdas(1) 5 1/17/06, 10:40:13 AM

6 6 Youdas et al was abducted, and the elastic band lengthened against the resistance provided by the stationary, nondominant LE. When the foot of the dominant side contacted the floor, the subject lifted the nondominant foot and adducted the thigh in a controlled manner through eccentric activation of the nondominant hip abductors. This sidestepping maneuver was performed for 45 seconds. On average, subjects completed between 35 and 40 sidesteps within the 45-second interval. After completing the resisted sidestepping, the subjects immediately assumed a single-limb stance on the nondominant leg. After 15 seconds, the examiner palpated the ASISs for proper placement of the goniometer. At the end of the 30-second interval, the examiner measured the pelvic-on-femoral position for the second time exactly as described for the baseline measurement. Data Analysis An intraclass correlation coefficient (ICC 3,1 ) 21 was calculated to estimate intratester reliability using data obtained from the 10 subjects who did not participate in the resisted-sidestepping exercise. These data were analyzed as suggested by Bland and Altman. 22 The mean difference and SD of the differences between the second and first measures of pelvic-on-femoral position (hip adduction) for the nondominant leg were calculated. From these data, the 95% limits of agreement (ie, the mean difference ± 1.96 SD of the difference) were calculated. 21 A visual plot was drawn of the change in pelvic-on-femoral position for all 42 subjects (baseline position minus postexercise position). To justify the use of parametric statistics, we examined the raw scores of pelvic-on-femoral position for both the baseline and the postexercise conditions. With the Shapiro Wilk goodness-of-fit test, we tested the assumption that the data came from a normal distribution. A mixed ANOVA was used to analyze the pelvic-on-femoral position for both men and women. The repeated factor, pelvic-on-femoral position, had 2 levels, baseline and postexercise position, and the between factor, sex, also had 2 levels. Statistical significance was established at α =.05. Results The ICC 3,1 estimating intratester reliability was.96, and the 95% confidence limits of agreement between the first and second measurements ranged from 0.9 to 2.3. The distribution of pelvic-on-femoral position data did not differ significantly from the normal distribution for both measure 1, P =.07 (baseline measurement of pelvic-on-femoral position), and measure 2, P =.24 (postexercise measure of pelvic-on-femoral position). Therefore, we used parametric statistics for analyzing the data. The pelvic-on-femoral positions for both men and women at baseline and immediately after the resisted-sidestepping exercise are shown in Figure 3. There was a statistically significant reduction in the pelvic-on-femoral position after the exercise protocol (F 1,40 = 38.3, P <.001). Baseline pelvic-on-femoral position was 85.8 ± 3.1 for men and 83 ± 2.6 for women. Posttest pelvic-on-femoral position was 84.1 ± 4.3 for men and 79.7 ± 2.6 for women. On average, the pelvic-onfemoral position was greater in men (85 ± 2.8 ) than in women (81.3 ± 2.8 ; F 1,40 = 16, P <.001). We did not, however, find a significant interaction effect; 01Youdas(1) 6 1/17/06, 10:40:14 AM

7 Hip-Abductor Muscle Performance 7 Figure 3 Pelvic-on-femoral position for the Trendelenburg test for both men and women at baseline and immediately after 45 seconds of resisted sidestepping using an elastic band. hence, the effect of the sidestepping exercise on pelvic-on-femoral position was not different between men and women (F 1,40 = 4.0, P =.052; β = 0.50). The change in pelvic-on-femoral position in degrees (baseline minus postexercise) between men and women is plotted in Figure 4. According to Figure 4, thirty-seven change scores (90%) differed from zero. Three change scores (8%) showed a negative change in the pelvic-on-femoral position after exercise; that is, the posttest pelvic-on-femoral position was greater in magnitude (hip in more abduction) than the pretest measurement. Thirty-four scores (92%) demonstrated a positive change in the pelvicon-femoral position after exercise, indicating that the posttest pelvic-on-femoral position was less than the baseline position (hip in more adduction). Comments Usefulness of the Trendelenburg Test The procedure we used to measure pelvic-on-femoral position and thus the function of hip abductors in single-limb stance (Trendelenburg test) using a goniometer can be performed easily in a clinical setting if the examiner can palpate the subjectʼs ASISs. We could not find other research reports that used this technique, but we believe it has clinical value, and it demonstrated clinically acceptable intratester reliability in the studied population. The task of palpating the ASISs might be a challenge, for example, in patients with excessive abdominal girth, because they are covered by a deep layer of subcutaneous tissue. 01Youdas(1) 7 1/17/06, 10:40:16 AM

8 8 Youdas et al Figure 4 Comparison of change in pelvic-on-femoral position in degrees (baseline minus postexercise) between men and women. The primary findings of this study support our research hypothesis and demonstrate that both men and women exhibited a significant reduction in pelvic-onfemoral position using the Trendelenburg test between baseline and 45 seconds of resisted sidestepping. Our data indicate that 45 seconds of resisted sidestepping against an elastic band was challenging to the nondominant hip abductors in 34 subjects. The reduction in pelvic-on-femoral position (hip adduction) after the exercise bout indicates that the hip abductors of the nondominant LE were unable to hold the pelvis in a horizontal or level position. Of the 34 subjects who showed a drop of ASIS on the non-weight-bearing side, only 7 demonstrated changes in pelvic-on-femoral position that were within the expected measurement error of 2. Therefore, 27 subjects (64%) demonstrated changes in pelvic-on-femoral position that exceeded this measurement error. It is likely that differences would have been even greater in a symptomatic population and if the exercise duration were longer. Previous studies have described weakness in the hip abductors after injury to the ankle or foot, 5,6 knee joint, 7-9,23 or low back. 24,25 These investigators detected weakness in the hip abductors using commercially available measurement devices. The test procedures were joint specific and measured hip-abductor performance in a non-weight-bearing position with the hip abductors undergoing a concentric or isometric activation pattern. Functionally, the hip abductors must control 01Youdas(1) 8 1/17/06, 10:40:17 AM

9 Hip-Abductor Muscle Performance 9 pelvic-on-femoral position in a weight-bearing position by acting eccentrically against the external demand created by the subjectʼs body mass or ground-reaction force. 3,4 Measuring frontal-plane pelvic-on-femoral position before and after a 45- second period of resisted hip abduction using an elastic band appears to be a useful test for identifying reduced abductor muscle performance. Reduced hip-abductor muscle performance might not be detected with a conventional MMT or dynamometer, because the duration of these tests (5 to 10 seconds) is short and the subjects are in a non-weight-bearing position. We envision a clinician using the sidestepping exercise with a patient who is recovering from an injury to the ankle foot complex, knee, hip, or low back, with possible dysfunction of the hip abductors. Furthermore, kinetic-chain problems might persist long after symptomatic recovery from an injury, yielding functional impairments that might be missed in a standard physical examination. 10,24,25 The test we describe might also be appropriate for the preparticipation physicals of subjects recovering from a lower extremity injury. The test would be useful for observing the symmetry between the right and left hip abductors and for providing clinicians with important decision-making information about the effectiveness of a rehabilitation program. Resistance Applied by SPRI Band During the sidestepping maneuver, the peak distance between the subjectʼs feet was generally between 50 and 75 cm, which translates to a deformation of the elastic band between 200% and 300% of resting length. On the basis of these dimensions, we predicted that the external load created an adduction force at the nondominant hip joint between 80 N and 130 N. Each of the 42 participants in the resisted-sidestepping exercise self-reported that they experienced fatigue in their hip-abductor muscles on completing the weight-bearing task. This intensity of the sidestepping exercise created fatigue of the subjectsʼ hip-abductor muscles according to their self-reports. This was confirmation to the investigators that the volume of exercise was appropriate. Study Limitations We have identified several limitations that need to be explored with further research. We tested only the hip abductors of the nondominant leg in healthy volunteers. Both sides should be tested and the symmetry of the change in pelvic-on-femoral position compared. These data would provide clinicians with important information on the expected changes in pelvic-on-femoral position after a demanding dynamic exercise in healthy volunteers. Another limitation of our study was the sample size of male volunteers. The present study was not powered to detect an interaction between time and gender, and the interaction was not statistically significant (F 1,40 = 4.40, P =.052). Therefore, we were unable to support our research hypothesis that women would demonstrate a greater change in pelvic-on-femoral hip abduction than would their male counterparts. Data illustrated in Figure 3, however, suggest that women might have had a more pronounced change in pelvic-on-femoral angle than men. In fact, based on a post hoc power analysis of the time-by-gender interaction, there is a high probability that we committed a type II error (β = 0.50) in stating that the interaction was not significant. The trend observed in Figure 3 suggests a 01Youdas(1) 9 1/17/06, 10:40:18 AM

10 10 Youdas et al potential differential effect of the exercise between genders and warrants closer investigation. According to the present results, in which the interactionʼs effect size (f) was approximately.30, a study that examines pelvic-on-femoral angle in 45 men and 45 women would have a statistical power (1 β) of.80 to detect a significant interaction. Moreover, we reported clinically acceptable intratester reliability for the measurement of pelvic-on-femoral position using a masked universal goniometer on 10 subjects who did not participate in the resisted-sidestepping exercise. We chose not to use a masked goniometer, however, when measuring pelvic-on-femoral position of the 42 study subjects. In retrospect, this might have introduced bias in the measurement process because the examiner could have anticipated a change in the pelvic-on-femoral position after a subject completed the sidestepping exercise. We would recommend that future studies use a masked goniometer when assessing pelvic-on-femoral position. Conclusion The results of our investigation indicate that healthy men and women demonstrate a significant change in the pelvic-on-femoral position (hip adduction) after a 45- second interval of resisted-sidestepping exercise using an elastic band. This indicates that the hip abductors can be challenged with a simple method of resistance, and the change in pelvic-on-femoral position can be measured using a goniometer while the subject is in static single-limb stance. Such a functional test could prove useful for clinicians when screening patients for possible impaired performance of the hip abductors after a lower extremity injury or when assessing the effectiveness of a current exercise program designed to strengthen the hip abductors. References 1. Neumann DA. Kinesiology of the Musculoskeletal System: Foundation for Physical Rehabilitation. St Louis, Mo: Mosby; Hardcastle P, Nade S. The significance of the Trendelenburg test. J Bone Joint Surg Br. 1985;67: Inman VT. Functional aspects of the abductor muscles of the hip. J Bone Joint Surg. 1947;29: Winter DA, Eng JJ, Ishac MG. A review of kinetic parameters in human walking. In: Craik RL, Oatis CA, eds. Gait Analysis: Theory and Application. 1st ed. St Louis, Mo: Mosby; 1995: Beckman SM, Buchanan TS. Ankle inversion injury and hypermobility: effect on hip and ankle muscle electromyography onset latency. Arch Phys Med Rehabil. 1995;76: Nicholas JA, Strizak AM, Veras G. A study of thigh muscle weakness in different pathological states of the lower extremity. Am J Sports Med. 1976;4: Jaramillo J, Worrell TW, Ingersoll CD. Hip isometric strength following knee surgery. J Orthop Sports Phys Ther. 1994;20: Fredericson M, Cookingham CL, Chaudhari AM, Dowdell BC, Oestreicher N, Sahrmann SA. Hip abductor weakness in distance runners with iliotibial band syndrome. Clin J Sport Med. 2000;10: Ireland ML, Wilson JD, Ballantyne BT, Davis IM. Hip strength in females with and without patellofemoral pain. J Orthop Sports Phys Ther. 2003;33: Youdas(1) 10 1/17/06, 10:40:19 AM

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