Electromyographic Analysis of Hip Rehabilitation Exercises in a Group of Healthy Subjects

STUDY DESIGN: Single-occasion, repeated-measures design. OBJECTIVE: To determine the magnitude of hip abductor muscle activation during 6 rehabilitation exercises. BACKGROUND: Many researchers have reported that hip strengthening, especially of the hip abductors, is an important component of a lower extremity rehabilitation program. Clinicians employ non-weight-bearing and weight-bearing exercise to strengthen the hip musculature; however, researchers have not examined relative differences in muscle activation during commonly used exercises. Information regarding these differences may provide clinicians with a scientific rationale needed for exercise prescription. METHODS AND MEASURES: Sixteen healthy subjects (mean +/- SD age, 27 +/- 5 years; range, 18-42 years; mean +/- SD height, 1.7 +/- 0.2 m; mean +/- SD body mass, 76 +/- 15 kg) volunteered for this study. Bipolar surface electrodes were applied to the right gluteus medius muscle. We measured muscle activation as subjects performed 3 non-weight-bearing (sidelying right hip abduction and standing right hip abduction with the hip at 0 degrees and 20 degrees of flexion) and 3 weight-bearing (left-sided pelvic drop and weight-bearing left hip abduction with the hips at 0 degrees and 20 degrees of flexion) exercises. Data were expressed as a percent of maximum voluntary isometric contraction of the right gluteus medius. Differences in muscle activation across exercises were determined using a 1-way analysis of variance with repeated measures, followed by a sequentially rejective Bonferroni post hoc analysis to identify differences between exercises. RESULTS: The weight-bearing exercises demonstrated significantly greater EMG amplitudes (P<.001) than all non-weight-bearing exercises except non-weight-bearing sidelying hip abduction. CONCLUSION: The weight-bearing exercises and non-weight-bearing sidelying hip abduction exercise resulted in greater muscle activation because of the greater external torque applied to the hip abductor musculature. Although the non-weight-bearing standing hip abduction exercises required the least activation, they may benefit patients who cannot safely perform the weight-bearing or sidelying hip abduction exercises. Clinicians may use results from this study when designing hip rehabilitation programs.