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Comparison of Gluteus Medius Muscle Electromyographic Activity During Forward and Lateral Step-up Exercises in Older Adults

V.S. Mercer, PT, PhD, is Associate Professor, Division of Physical Therapy, Department of Allied Health Sciences, University of North Carolina at Chapel Hill, CB #7135, Bondurant Hall, Suite 3022, Chapel Hill, NC 27599-7135 (USA).
M.T. Gross, PT, PhD, FAPTA, is Professor, Program in Human Movement Science, Division of Physical Therapy, Department of Allied Health Sciences, University of North Carolina at Chapel Hill.
S. Sharma, PT, MPT, is Staff Physical Therapist, Sports & More Physical Therapy Inc, Cary, North Carolina.
E. Weeks, PT, MPT, is Staff Physical Therapist, Carolinas Rehabilitation (Main), Charlotte, North Carolina.

vmercer{at}med.unc.edu

Background: Step-up exercises often are suggested for strengthening the hip abductor muscles and improving balance in older adults. Little is known, however, about whether the forward or lateral version of these exercises is best for activating the hip abductor muscles.

Objective: The purpose of this study was to examine the electromyographic (EMG) amplitude of the gluteus medius (GM) muscles bilaterally during forward and lateral step-up exercises.

Design: The study design involved single-occasion repeated measures.

Methods: Twenty-seven community-dwelling adults (7 men and 20 women) with a mean (SD) age of 79.4 (8.0) years performed forward and lateral step-up exercises while the surface EMG activity of the GM muscles was recorded bilaterally. Pressure switches and dual forceplates were used to identify the ascent and descent phases. Subjects were instructed to lead with the right lower extremity during ascent and the left lower extremity during descent. Differences in normalized root-mean-square EMG amplitudes with exercise direction (forward versus lateral) and phase (ascent versus descent) were examined by use of separate repeated-measures analyses of variance for the right and left lower extremities. The alpha level was set at .05.

Results: Gluteus medius muscle EMG activity was significantly greater for lateral than for forward step-up exercises for the left lower extremity during the ascent phase and for both lower extremities during the descent phase. In addition, right GM muscle EMG activity was significantly greater during ascent than during descent for both exercise directions.

Limitations: Study limitations include use of a convenience sample and collection of limited information about participants.

Conclusions: Step-up exercises are effective in activating the GM muscle, with lateral step-up exercises requiring greater GM muscle activation than forward step-up exercises. Further study is needed to determine whether exercise programs for hip abductor muscle strengthening in older adults should preferentially include lateral over forward step-up exercises.

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