Trapezius Activation During Bilateral Scapular Retraction With Shoulder External Rotation: The Incorporation of Knetic Chain and Unstable Surface

Maintaining muscular balance among the scapular stabilizers is crucial for optimal shoulder function. The Bilateral Scapular Retraction with Shoulder External Rotation (BSR-SER) exercise is frequently used in clinical rehabilitation to activate the lower trapezius while minimizing upper trapezius activity. Although this exercise is widely practiced, the effects of performing it under kinetic chain conditions (such as squat and lunge positions) and on an unstable surface have not been thoroughly explored.

This study will examine how adding kinetic chain involvement and instability influences the electromyographic activity of the upper trapezius (UT), middle trapezius (MT), and lower trapezius (LT) muscles during the BSR-SER exercise. Twenty healthy participants will perform the exercise in various lower extremity positions (standing, squat, lunge) and on both stable and unstable surfaces using a BOSU® ball. EMG data will be collected using a wireless surface EMG system and analyzed in terms of percentage of maximal voluntary isometric contraction (%MVIC).

The results of this study may provide valuable insights into the optimization of scapular stabilization exercises and guide clinicians in designing more effective shoulder rehabilitation programs by incorporating kinetic chain principles and unstable surfaces.