Effect of TheraBand-Based Throwing Exercises on Glenohumeral Rotational Kinematics, Scapular Dyskinesis, and Spiking Performance in Volleyball Players with Shoulder Internal Rotation Deficit: A Randomized Controlled Trial

Abstract Background: Glenohumeral Internal Rotation Deficit (GIRD) in overhead athletes represents a significant concern in volleyball, yet most research focuses solely on range of motion improvements without assessing biomechanical adaptations or sport-specific performance outcomes. Objective: This study evaluated the efficacy of a 12-week TheraBand-based throwing exercise program on glenohumeral rotational kinematics, scapular dyskinesis, and spiking performance in college volleyball players with shoulder internal rotation deficit Methods: A parallel-group, single-blind randomized controlled trial enrolled 64 male collegiate volleyball players (age 20.3±1.8 years) with documented GIRD (≥10°) and scapular dyskinesis. Participants were randomized to either an intervention group receiving TheraBand-based external rotation and scapular stabilization exercises three times weekly (n=32) or a control group receiving standard care (n=32). Primary outcomes included dominant shoulder Internal Rotation Range of Motion (IR ROM), GIRD measurements, and glenohumeral External/Internal Rotation Ratio (ER/ IR). Secondary outcomes encompassed scapular upward rotation and posterior tilt measured at 90° of humeral elevation using digital inclinometry, spike velocity via radar gun, spike accuracy through video analysis, Y-Balance Test-Upper Quarter composite scores, and rotator cuff strength asymmetry indices measured via isokinetic dynamometry. Results: Intervention group participants demonstrated significant improvements in all primary and secondary outcomes compared to control group. Mean IR ROM increased from 58.4°±9.2° to 71.3°±7.5° (p