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<0.001, Cohen's d=1.42). GIRD decreased from 14.8°±3.5° to 2.8°±2.1° (p<0.001, d=1.87). Scapular upward rotation improved from 38.2°±6.4° to 48.7°±5.8° at 90° humeral elevation (p<0.001, d=1.53). Spike velocity increased from 78.2±6.4 km/h to 87.4±5.9 km/h (p<0.001, d=1.24). Spike accuracy improved from 72.3%±8.1% to 84.6%±7.3% (p<0.001, d=1.52).

Conclusion: TheraBand-based throwing exercises targeting external rotator strength and scapular stabilization effectively resolved GIRD while simultaneously improving glenohumeral kinematics, normalizing scapular dyskinesis patterns, and enhancing sport-specific volleyball performance metrics. This integrated approach addresses the biomechanical kinetic chain dysfunction underlying shoulder pathology in overhead athletes, providing evidence for precision physiotherapy management combining tissue adaptation and functional performance optimization.