STUDY DESIGN: Prospective single-group repeated-measures design. OBJECTIVES: To quantify electromyographic (EMG) signal amplitude of the gluteus maximus, gluteus medius, vastus medialis oblique, and biceps femoris during 5 unilateral weight-bearing exercises. BACKGROUND: Using normalized EMG (NEMG) signal amplitude as a measure of muscle activation and, therefore, an estimate of exercise intensity, the relative contributions and interac­tion of the hip and thigh muscles during unilateral weight-bearing exercise can be examined. With regard to potential efficiency for strengthening, data on the amount of EMG signal amplitude for these 4 muscles during commonly used exercises are limited. METHODS AND MEASURES: Twenty-three healthy, asymptomatic subjects (16 men, 7 women; mean ± SD age, 31.2 ± 5.8 years) participated. A repeated-measures analysis was conducted using general linear models. The percent maximum voluntary isometric contraction was measured within each subject across 4 muscles during 5 exercises for 2 sepa­rate trials. Effect sizes of pairwise comparisons were computed. RESULTS: Statistically significant differences were noted in the amount of mean NEMG signal amplitude for the 4 muscles across the 5 ex­ercises. A similar recruitment pattern between muscles was observed across all exercises. CONCLUSION: Even though all muscles except the biceps femoris demonstrated mean NEMG signal amplitudes sufficient for strength­ening, the wall squat produced the highest levels of activation and should be considered the most efficient for targeting any of the 4 muscles or for training a cooperative effort among the muscles. 

J Orthop Sports Phys Ther. 2007;37(2):48-55. doi:10.2519/jospt.2007.2354

KEY WORDS: gluteus maximus, gluteus me­dius, lower extremity, step-up, wall squat