SURFACE ELECTROMYOGRAPHY OF PECTORALIS MAJOR AND ANTERIOR DELTOID IN THE BENCH PRESS FROM 40% 1RM TO 100% 1RM

Background. Bench press (BP) is a common upper body resistance training exercise. This study aims to explore the muscle activation (MA) of pectoral major (PM) and anterior deltoid (AD) in BP during an incremental protocol from 40% to 100% one repetition maximum (1RM).  Methods. Ten strength-trained males (aged 24.3±3.0 years; height 176.2±5.0 cm; weight 77.7±9.5 kg; resistance training experience 5.9±2.5 years, 1RM 96.5±14.7 kg; 1RM/BW 1.2) were monitored with surface electromyography during an incremental protocol of six loads from 40% 1RM to 100% 1RM in BP. Two repeated measures ANOVA were used to detect the difference in the signal's amplitudes (µV) RMS between relative percentage loads (40%, 60%, 70%, 80%, 90%, 100% 1RM) within each muscle being monitored (PM, AD) and an independent sample T-test was used to detect a significant difference in the MA between the right and left side.   Results. Overall, concerning PM, there are no differences in MA between 60% to 100% 1RM; similarly, there are no differences in MA of AD between 70% to 100% 1RM. T-test shows that there is no significant difference between the right and left side of the PM (right = 644.83±212.37 µV; left= 665.30±273.14 µV; p = 0.324) and AD (right = 956.42±487.25 µV; left = 951.61±474.85 µV; p = 0.478).  Conclusion. This study shows that MA of PM and AD increases from light (50% 1RM) to high load (≥70% 1RM) in a strength-trained population and that, against weight room general belief, BP is a symmetric exercise.