CONCENTRIC ISOKINETIC STRENGTH OF SHOULDER ROTATOR MUSCLES IN TENNIS PLAYERS

Abstract

The primary purpose of this study was to perform isokinetic peak torque measurements of the gleno-humeral joint during internal and external rotation, and to evaluate external/internal peak torque ratios in competitor tennis players. The other purposes were to determine any significant differences between the dominant and non-dominant extremities, and also between the athlete and control groups. Nineteen healthy trained tennis players and nine sedentary subjects were tested bilaterally on an isokinetic dynamometer at angular speeds of 60, 180 and 240º/s for concentric internal and external rotation of the shoulder joint, with the arm in 90º of abduction, and the elbow in 90º of flexion. Testing guidelines and a standardized protocol were strictly followed. The Wilcoxon Signed-Ranks Test was used to test for differences in isokinetic measurements between extremities, and the Mann-Whitney U Test was used to assess differences between groups. Significantly higher peak torque figures for internal rotation of the dominant shoulder, and significantly higher external/internal rotation ratios of the non-dominant shoulder were found at each testing speed, in tennis players. Statistically significant differences were found between the groups for all parameters, in favor of athletes. The results of this study are relevant in pointing to the maintenance of muscle strength balance in athletes who perform predominantly using unilateral upper extremity movement patterns, as a means to possibly reduce the risk of overload injuries.