Impact of shoulder abduction angle on peak force and myoelectric activity during maximal isometric bench press in resistance-trained men

The purpose of this study was to investigate the infl uence of shoulder abduction positions (45° vs. 90°) on peak force (PF) production and myoelectric activity (sEMG) of the upper and lower pectoralis major (UPM, LPM), anterior deltoid (AD), and long head of the triceps brachii (TB) during maximal isometric bench press in resistance-trained men. Twelve young, resistance-trained men (age: 24.7 ± 4.2 years) participated in a quasi-experimental, within-subject study. Each subject performed three maximal isometric bench press contractions for both shoulder abduction positions, during which PF and sEMG (UPM, LPM, AD, and TB) were measured. Statistical analyses included paired t-tests for PF and two-way ANOVA for sEMG. Results showed no signifi cant diff erence in PF between 45° and 90° shoulder abduction positions. For sEMG, post hoc analyses revealed signifi cant diff erences between muscles within each shoulder position: at 45°, AD vs. UPM (Δ% = 41.5%), AD vs. LPM (Δ% = 65.4%), and UPM vs. LPM (Δ% = 40.8%); at 90°, AD vs. LPM (Δ% = 61.9%) and UPM vs. LPM (Δ% = 41.2%). These fi ndings suggest that shoulder abduction position (45° vs. 90°) does not aff ect maximal isometric force production or substantially alter myoelectric activation patterns in resistance-trained men.