Activation levels of gluteus medius during therapeutic exercise as measured with electromyography: a structured review

Abstract

Background: Strengthening exercise for gluteus medius (GMed) is an important management strategy for lower limb disorders such as osteoarthritis and patello-femoral syndrome, and exercises in functional positions are commonly prescribed. Electromyography (EMG) can be used to measure muscle activation to ascertain the extent of muscle recruitment during exercise.

Objectives: To review the available evidence on the magnitude of GMed activation measured with EMG during therapeutic exercise.

Methods: A structured review of studies which measured EMG magnitude of GMed during a range of therapeutic exercises was undertaken. Amplitude levels of GMed were reported as a percentage of maximum voluntary isometric contraction.

Results: Fifteen studies were included. Most of these were conducted on asymptomatic volunteers, with three studies investigating individuals with knee or hip pathology. A wide range of exercises was investigated in both weightbearing (WB) and nonweightbearing (NWB) positions. In general, EMG activation was greater in WB positions but variation occurred across studies. Many exercises were below levels considered necessary for strength gains. Generally, methodological quality was good but there was variation in the reporting of technical aspects of the study. Many of the studies did not acknowledge the range of limitations of EMG in measuring muscle activation in therapeutic exercise.

Conclusions: The results provide some information regarding GMed recruitment during exercise, although there were some discrepancies in results between studies which may be due to factors related to EMG measurement and recording as well as the execution of the exercise. Extrapolation of results to symptomatic populations in a clinical setting islimited.