Comparison of isokinetic strength of shoulder rotator muscles among volleyball players with and without scapulae dyskinesia

Introduction: Change in scapula normal kinematic and scapula-thoracic rhythm cause scapulae dyskinesia. Scapulae Dyskinesia is defined as abnormal position and movement of scapula. The prevalence of scapulae dyskinesia in volleyball players and the resulting muscular dysfunction in these players have made present paper to study isokinetic strength of shoulder internal and external rotator muscles in volleyball players with and without scapulae dyskinesia.
Methods: 30 volleyball players aged 18 to 25 with experience of playing in one of the top three leagues (Premier League, First Division League, Omid League) were selected non-randomly and purposefully and were divided into two groups of 15 players with and without scapulae dyskinesia. Isokinetic Dynamometer system was used to measure maximum concentric torque of shoulder internal rotators and maximum eccentric torque of shoulder external rotators during 90º arm abduction at a speed of 60 and 120 degree per second. Date were analyzed using Multivariate Analyze of Variance (MANOVA) test at the significance level α ≤ 0.05.
Results: Maximum eccentric torque of shoulder external rotators and functional strength of dominant leg were significantly lower in volleyball players with scapulae dyskinesia. However, 2 groups did not have significant difference in maximum concentric torque of shoulder internal rotators.
Conclusion: Volleyball players with scapulae dyskinesia had more muscular balance deficiency between internal and external rotator muscle of shoulder. So that these players may have probably insufficient eccentric strength at shoulder external rotators and this insufficiency may result in decrease of shoulder functional strength.