Isokinetic Measurement of a Concentric and Eccentric Strength of the Rotators in Throwing

The shoulder injury was resulted from muscle imbalance between acceleration and deceleration during the throwing. The agonist-antagonist muscle strength relationship for throwing was formerly described as functional ratios of eccentric external rotator to concentric internal rotator moments and eccentric internal rotator to concentric external rotator moments. The purpose of this study was to measure the ratio of concentric and eccentric strength of the shoulder rotators by isokinetic muscle performance in Korean throwing college athletes for descriptive data. On 10 dominant shoulders of asymptomatic throwing college athletes applying Cybex II isokinetic dynamometer, concentric and eccentric muscle strength of the rotators were measured at the speed of 90/s, 180/s, 240/s. Maximal torque ratio of the eccentric strength of the external rotator against the concentric strength of the internal rotator was 1.25, 1.13, 1.21 at the each speed. The functional external eccentric-to-internal concentric ratio was similar with previous published studies. There was no significant difference between each speed. Eccentric strength of the external rotator was higher than concentric strength of the internal rotator during internal and external rotation at all speeds. This functional assessment of strength testing that reflected the importance of eccentric external rotation strength for the dynamic shoulder joint stability during the throwing. Therefore, the increase of the eccentric strength of the external rotator would be helpful to prevent the shoulder injury and to treat for rehabilitation of injured shoulder.