The changes in shoulder rotation strength ratio for various shoulder positions and speeds in the scapular plane between baseball players and non-players

[Purpose] This study aimed to investigate the effect of shoulder positions and speeds on internal and external rotation torque of college baseball players and age-matched non-players. [Subjects] Twenty first-level collegiate baseball players and 19 college students were recruited. [Methods] A dynamometer system was used to evaluate the shoulder rotation strength in sitting postures. Three testing positions, namely shoulder abduction of 45 degrees, 70 degrees, and 90 degrees in the scapular plane, were combined with three testing speeds at 60 degrees/s, 120 degrees/s, and 210 degrees/s. [Results] The maximum external and internal rotation torques both occurred at shoulder abduction of 70 degrees. However, only external rotation torque was affected by the speed, with the peak value observed at 60 degrees/s. The internal rotation torque of baseball players was larger than that of the control group under all testing conditions, but the external rotation did not show any difference. The ratio of external to internal rotation torque changed with the testing positions and speeds in both groups. The ratio in the control group was greater than that in the player group. [Conclusion] The shoulder position could affect the rotational strength, and the baseball players could strengthen their external rotators for better performance and injury prevention.