Gluteal muscle activity during weightbearing and non-weightbearing exercise

Researchers suggest that decreased strength of the gluteus medius (GMed) and the gluteus maximus (GMax) muscles contributes to the etiology of various orthopedic pathologies of the knee. Currently, equivocal evidence exists regarding Electromyography (EMG) activity of gluteal musculature during weightbearing (WB) and non-weightbearing (NWB) exercise. The purpose of this study was to compare GMed and GMax muscle activation during WB functional exercise and NWB 10 repetition maximum (RM) exercises.

Surface EMG electrodes recorded the muscle activity of the GMax and GMed as subjects performed three sets of 10 repetitions of the following exercises: (1) forward step-up, (2) lateral step-up, (3) 10 repetition maximum (10 RM) side-lying hip abduction and (4) 10 RM prone hip extension. The 10 RM resistances were determined one week prior to data collection.

The GMed was recruited significantly more during side-lying 10 RM than the remaining exercises (side-lying, 99.9±17% vs. lateral step-up, 61±20%; Forward step-up, 62.7±18.2%; prone, 38±22.2%)(p<0.001). The GMax was recruited to the greatest extent during prone 10 RM hip extension (prone, 100.7±14.5% vs. forward step-up, 28.7±18.7%; lateral step-up, 31±19.9%; side-lying, 38±23.3%)(p<0.001).

These results suggest that performing a 10 RM NWB exercise results in greater muscle activation than two functional WB exercise without load in young, healthy individuals. In addition, forward and lateral step-ups failed to effectively recruit the GMax at a high enough level to achieve a strengthening stimulus. The GMed was recruited to a higher extent than the GMax during the stepping tasks which might be further augmented if the activity is performed with an additional external load.

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