The relationship of elbow alignment and kinematics on shoulder torque during the softball pitch: a biomechanical analysis of female softball pitchers

Background: Female softball pitchers commonly throw more pitches per game and season than their baseball counterparts. The greatest stress to the shoulder during a softball windmill pitch is at ball release (BR). This study investigated shoulder torques at BR among female softball pitchers and identified relationships to the kinematics of the elbow and forearm and alignment of the elbow (carrying angle and elbow extension). Methods: High-speed 3-dimensional biomechanical analyses were performed in 33 pitchers (25 high school, 8 collegiate). Elbow and shoulder biomechanics at BR during fastball pitches and goniometric measures of carrying angle and elbow extension were collected and analyzed. Results: Carrying angle correlated positively with shoulder extension torque at BR (r(s) = 0.371, P = .048) and forearm pronation at BR (r(s) = 0.370, P = .048). During the windmill pitch, the greater the elbow flexion, the greater shoulder adduction torque at BR (r(s) = -0.522, P = .007). Multiple regression analysis revealed that the carrying angle, passive elbow extension, and elbow flexion/extension angle at BR predicted shoulder flexion/extension torque at BR (F-3.24 = 3.463, R-2 = .302, P = .032.) Conclusions: Our findings demonstrate that shoulder torques during the softball fastpitch are influenced by the carrying angle and the kinematic elbow flexion angle at BR. Sports medicine clinicians and coaches should consider the role that the elbow carrying angle plays in creating shoulder stress when treating and training fastpitch softball players. (C) 2018 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.