Electromyographic Analysis of Left and Right Side Gluteus Medius in Unilateral and Bilateral Bodyweight Exercises

Abstract

A wide variety of exercises directed at gluteus medius muscle (Gmed) activation are used both in athletic performance and for rehabilitation. A common way to increase the load on Gmed is to change from a bilateral (BI) to a unilateral (UNI) stance in the same exercise. Muscle activation levels ≥40 %MVIC are suggested for strength gains, however, muscle activity lower than that may be useful in developing muscle endurance. Despite numerous studies investigating which exercises best target Gmed, only muscle activity on one side of the body has been investigated, and knowledge about how an exercise affects both left and right side Gmed in BI and UNI stance is lacking. PURPOSE: To investigate the single and combined muscle activity magnitude in left and right side Gmed during standing and supine bodyweight exercises performed bilaterally and/or unilaterally. METHODS: 15 healthy college-aged subjects performed squat and supine bridge exercises in both a BI and UNI stance, and a UNI standing hip abduction exercise. The dominant (DOM) leg acted as the supporting leg in UNI exercises. Gmed electromyography activity from both left and right side was collected during the 3 exercises and normalized to a maximal voluntary isometric contraction (MVIC). Average μV was collected for 3 repetitions (paced at 2 s) of each exercise (total 6 s). RESULTS: During the squat, Gmed activity in the DOM leg had a significantly higher (p<0.01) muscle activity in UNI (36.7 %MVIC) compared to BI (9.4 %MVIC) stance, whereas Gmed in the non-DOM leg was similar for both stances (UNI 10.7 and BI 9.9 %MVIC; p=0.63). During supine bridge, Gmed in DOM leg was significantly increased (p<0.01) in UNI (33.2%MVIC) compared to BI (14.7 %MVIC). In contrast, the non-DOM leg displayed a significant lower activity (p<0.01) in UNI (7.0%MVIC) compared to BI (15.3%MVIC) stance. For UNI standing hip abduction DOM leg (34.5 %MVIC) had higher muscle activation (p<0.01) compared to non-DOM leg (24.7%MVIC). CONCLUSION: Highest total muscle activity (left and right side) in Gmed was found in standing hip abduction, whereas Gmed maximum activity on one side only was similar for the DOM leg in UNI stance in all three exercises (33-37% bridge, hip abduction, squat). Knowledge about Gmed activation magnitude on both sides can aid in selection of strengthening exercises which targets Gmed.