Shoulder muscle activation during overhead squat: effects of elastic resistance direction on kinetic chain dynamics

Introduction: The overhead squat is a complex movement that engages multiple segments of the kinetic chain. However, the interaction between electromyographic activity and elastic resistance within this context remains insufficiently understood. Objective: This study examined how different configurations of elastic resistance influence the activation of shoulder and axiohumeral muscles during the OHS. Methodology: Surface electromyography was used to record muscle activity in 19 healthy male participants, divided into two elastic resistance groups, while performing the OHS under three resistance conditions. Non-parametric statistical analysis were applied. Results: Significant differences in muscle activation were observed across resistance conditions in both elastic resistance groups. Higher resistance levels were associated with increased activation of the anterior deltoid (AD), upper trapezius (UT), and latissimus dorsi (LD). Activation ratios revealed reduced reliance on prime movers during arm elevation. Discussion: Elastic resistance effectively modulates shoulder muscle recruitment, particularly enhancing scapular stabilization through greater activation of the lower trapezius and serratus anterior. The latissimus dorsi also contributes to trunk control and energy transfer along the kinetic chain. Conclusions: Findings support the integration of resistance direction and magnitude into rehabilitation strategies to optimize neuromuscular control in individuals with shoulder dysfunction.