Background: This study aimed to compare the muscle activity between the symmetric and selected asymmetric loads (2.5%; 5% and 7.5% differences in load position between sides of the bar) during the flat bench press (BP) exercise at 70%1RM. The study included 10 resistance-trained males (25.3 ± 2.3 years; 82.9 ± 6.9 kg; 177.8 ± 4.5 cm; 1RM BP: 104.5 ± 8.6 kg; experience: 5.6 ± 1.5 years).
Methods: To assess the differences in muscle activity between both sides of the body and load placement, the participants performed several attempts of the BP with symmetric and asymmetric load at 70%1RM in a random order (symmetric; 2.5%; 5% and 7.5% differences in load position between sides of the bar). Peak muscle activity of dominant and non-dominant body-side was recorded for the pectoralis major (PM), anterior deltoid (AD), and the long head of the triceps brachii (TB).
Results: A two-way repeated-measures analysis of variance (ANOVA) indicated a statistically significant main interaction between side and load (p < 0.01) for AD, PM and TB muscles.
Conclusion: The results of this study showed that asymmetrically loaded BP leads to significantly higher muscle activity on the loaded side of the body. The offset training method during bilateral resistance exercise may be an effective and simple approach for reductions in muscle imbalances and improvement in bilateral exercise performance.
Keywords: bilateral movement; injury and prevention; performance; resistance exercise.