Comparison of electromyographic activity of the superior and inferior portions of the gluteus maximus muscle during common therapeutic exercises

Abstract

STUDY DESIGN: Controlled laboratory study, repeated-measures design. BACKGROUND: Previous studies have reported that the superior and inferior portions of the gluteus maximus have different functional roles. Knowledge of how the different portions of the gluteus maximus are activated during therapeutic exercise may lead to more specific exercise prescription. OBJECTIVE: To compare muscle activation of the superior and inferior portions of the gluteus maximus during commonly used therapeutic exercises. METHODS: Twenty healthy persons participated. Electromyographic (EMG) signals were obtained from the superior and inferior portions of the gluteus maximus using fine-wire electrodes. Normalized EMG signal amplitudes were compared between the superior and inferior gluteus maximus across 11 exercises using a 2-way repeated-measures analysis of variance. RESULTS: The superior portion of the gluteus maximus had significantly greater relative EMG activity than the inferior portion of the gluteus maximus during exercises that incorporated elements of hip abduction and/or external rotation (5 of 11 exercises evaluated). There was no significant difference in activation between the superior and inferior portions of the gluteus maximus during the remaining 6 exercises. CONCLUSION: The results of the present study demonstrate preferential activation of the superior portion of the gluteus maximus during exercises that incorporate elements of hip abduction and/or external rotation. In contrast, exercises that primarily involve hip extension target both portions of the gluteus maximus to a similar extent.