The purpose of this study was to investigate the scapulohumeral rhythm and isometric strength ratio of shoulder agonist to antagonist muscles in handball players and non-athletes. 40 subjects (20 handball players, age: 22.21±2.1 years, and 20 non-athletes, age: 22.21±2.3 years) volunteered for this study. Manual Muscle Test (MMT) was used to measure isometric strength of shoulder muscles and two inclinometers were used to measure humeral and scapula range of motion. Scapulohumeral rhythm was calculated from division humeral elevation to upward rotation of the scapula at 45°, 90°, and 135°, from 45° to 90° and from 90° to 135° abduction in frontal plane.
There is no significant difference in ratio of agonist to antagonist muscles between dominant and non-dominant shoulder in non-athletes; while there is significant difference in ratio of abductor to adductor muscles (p=0.002) between dominant and non-dominant shoulder in handball players. Also, there is no significant difference in scapulohumeral rhythm at different angles of abduction between dominant and non-dominant shoulder in non-athletes while there is significant difference in scapulohumeral rhythm at 90° (p=0.01), 135° (p=0.02) and from 45° to 90° abduction (p=0.02) between dominant and non-dominant shoulder. Wesuggest shoulder muscles balance (abductor to adductor especially) in dominant shoulder of overhead throwers that perform their activities unilaterally for prevention of perturbation of scapulohumeral rhythm.