Fifty-six right-handed male participants with strength training experience performed dumbbell elbow flexion exercises while surface electrodes recorded biceps brachii activity. The researchers used two predefined exercise sequences performed in reversed order to reduce potential order and fatigue effects, a control measure intended to limit systematic bias in the acute EMG recordings.

The amplitude results followed a consistent pattern. In pronation, with palms facing down, right-arm EMG activity averaged 215 microvolts. Switching to a neutral grip raised the signal by 106 microvolts, and full supination added a further 100 microvolts. On the left side, pronation produced 249 microvolts, rising by 188 microvolts in neutral and by another 93 microvolts in supination.

Effect sizes, reported as Cohen’s dz, indicated moderate-to-large differences in recorded sEMG amplitude between the forearm positions, meaning the grip-related differences were not only statistically significant but also substantial in practical magnitude. Supination consistently elicited the highest biceps brachii activation and pronation the lowest across both arms, with neutral grips falling between the two extremes in every comparison.

The authors suggest that forearm position may be an important factor to consider when selecting dumbbell exercises aimed at increasing biceps brachii muscle activity, offering practical insight for coaches, athletes and rehabilitation specialists. They note, however, that the study examined acute EMG responses in a single muscle during one exercise type in a specific population, and that future research should explore additional muscle groups and exercise variations to refine training strategies and enhance performance outcomes.

Subject of Research: Acute effects of forearm position on biceps brachii electromyographic activity during dumbbell elbow flexion

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

Article References: Pakosz, P., Konieczny, M., & Domaszewski, P. (2026). Optimizing hypertrophic strength training: electromyographic effects of forearm position on biceps brachii activity. Scientific Reports. https://doi.org/10.1038/s41598-026-75583-0

Image Credits: AI Generated

DOI: 10.1038/s41598-026-75583-0

Keywords: electromyography, biceps brachii, forearm position, supination, pronation, strength training, hypertrophy, dumbbell exercise, muscle activation, surface EMG, Optimizing, hypertrophic