Electromyographical Analysis of selected Lower Extremity Muscles During 5 Unilateral Weight-Bearing Exercises

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.