Background: understanding of adaptations in unilateral and bilateral athlete’s shoulders can provide good information for clinicians and sport trainers. Objective: The aim of this study was to investigate the comparison of scapulohumeral rhythm, flexibility, posterior capsule stiffness and shoulder muscle strength in unilateral and bilateral overhead athletes. Methods: Thirty subjects (15 volleyball players with 18.73±1.79 years old as unilateral overhead and 15 swimmers with 17.75±1.6 years old as bilateral overhead) participated in this study volunteered. An inclinometer was used to measure scapulohumeral rhythm, posterior capsule stiffness, and shoulder internal and external rotation. Nicholas hand dynamometer was also used to evaluate the isometric strength of internal and external shoulder rotators. ANOVA with repeated measure test was used to investigate within and between different group effects. A significance level was set at 0.05. Results: findings indicated there are significant differences between dominant shoulders of volleyball players and swimmers in scapulohumeral rhythm in 0-45˚ (p=0.04), 0-90˚ (p=0.04), 0-135˚ (p=0.04) humeral elevation, normalized isometric strength of internal rotators (p=0.01), shoulder external rotation (p=0.01), posterior capsule stiffness (p=0.01), normalized length of pectoralis minor muscle (p=0.02). Also, there are significant differences between non-dominant shoulders of the scapulohumeral rhythm in 0˚ to 45˚ (p=0.01), 0˚ to 90˚ (p=0.01), 0˚ to 135˚ (p=0.01) humeral elevation, shoulder internal rotation (p=0.03) and posterior capsule stiffness (p=0.01). Conclusion: This study demonstrates a potential effect of type sport and dominance or non-dominance limb on asymmetric musculoskeletal adaptations of the shoulder complex we recommend considering individual compensatory exercises to optimize these asymmetries and prevent sports injuries.
