Optimizing hypertrophic strength training: electromyographic effects of forearm position on biceps brachii activity

This study examined the acute effect of three forearm positions (supination, neutral, and pronation) on biceps brachii sEMG amplitude during a standardized hypertrophy-oriented resistance exercise. While the optimal forearm position for maximizing muscle engagement in dumbbell exercises remains debated, this research utilizes surface electromyography (sEMG) to provide practical insights for coaches, athletes, and rehabilitation specialists. Fifty-six right-handed male participants with strength training experience performed elbow flexion exercises with dumbbells while biceps brachii activity was recorded using surface electrodes. Two predefined sequences with reversed order were used to reduce potential order and fatigue effects. sEMG analysis revealed significant differences in biceps brachii activation across forearm positions. In pronation, right-arm EMG activity averaged 215 µV, increasing by 106 µV in neutral and an additional 100 µV in supination. On the left side, pronation resulted in 249 µV, rising by 188 µV in neutral and 93 µV in supination. Cohen’s dz effect sizes indicated moderate-to-large differences in recorded sEMG amplitude between forearm positions. Forearm rotation significantly affected biceps brachii sEMG amplitude, with the highest values observed during supination and the lowest during pronation. These findings suggest that forearm position may be an important factor to consider when selecting dumbbell exercises aimed at increasing biceps brachii muscle activity. Future research should explore additional muscle groups and exercise variations to refine training strategies and enhance performance outcomes.