Isokinetic Fatigue Ratio of Shoulder Rotators in Elite Softball Players With and Without Rotator Cuff Tendinopathy, and its Association With the Subacromial Space.

Abstract

Fatigue of the shoulder rotators may cause reduction of the subacromial space (SAS) and contribute to rotator cuff tendinopathy. To compare the isokinetic peak torques and fatigue ratios of shoulder external rotators (ER) and internal rotators (IR) between elite softball athletes with and without rotator cuff tendinopathy and to investigate their associations with the SAS. Cross-sectional study. University laboratory. Twenty-five elite softball players and 31 asymptomatic sedentary controls participated in this study. Isokinetic concentric IR and ER peak torque and fatigue ratio were measured at 60°/s and at 180°/s, respectively; and ultrasound measurement of the SAS was measured during 0° and 60° of shoulder abduction. Athletes with rotator cuff tendinopathy demonstrated lower peak torque in shoulder concentric ER when compared with their healthy counterparts (37.8 [5.8%] vs 43.6 [8.5%]). No significant difference was found in the fatigue ratios of ER, IR, and ER/IR when compared between elite softball athletes with and without rotator cuff tendinopathy (all P > .24). In asymptomatic athletes, greater IR peak torque (r = .583, P = .03), lower ER/IR strength ratio (r = -.605, P = .02), and greater ER/IR fatigue ratio (r = .575, P = .03) were moderately associated with more reduction of the SAS during 0° and 60° of shoulder abduction. Decreased strength ratio and fatigue ratio of ER/IR were related to reduction of the SAS.