Trapezius Muscle Activation During Bilateral Scapular Retraction and Shoulder External Rotation Under Kinetic Chain and Unstable Surface Conditions

Participants perform the Bilateral Scapular Retraction with Shoulder External Rotation (BSR-SER) exercise using a resistance band. The exercise is conducted under various conditions including stable and unstable surfaces (using BOSU® balance trainer) and in three different lower limb positions: standing, lunge, and squat. Each condition is randomized, and participants complete all conditions in a crossover design. The intervention aims to evaluate trapezius muscle activation patterns during these exercises using surface electromyography (EMG).