Influence of Repetitive Pitching on Joint Range of Motion and Muscle Flexibility of Junior High School Baseball Pitchers

Abstract

[Purpose] The purpose of this study was to clarify the influence of repetitive pitching by adolescent baseball pitchers on joint range of motion (ROM) and muscle flexibility. [Participants and Methods] Body function of 29 pitchers who belonged to junior high school baseball teams was measured before and after a repetitive 75-throw sequence. Measurement items included joint ROM, muscle flexibility, angle of thoracic kyphosis, latissimus dorsi muscle strength, and posterior shoulder tightness. The speed of the pitched balls was measured as an indicator of performance. [Results] Throw-side shoulder joint internal rotation ROM, non-throw-direction trunk rotation ROM, and non-throw-side gastrocnemius muscle flexibility decreased significantly after the throwing sequence, throw-side hip joint inner rotation ROM increased significantly, while pitched-ball speed showed no significant change. [Conclusion] Adolescent baseball players are more likely affected than adults baseball players by rupture of the kinetic chain. Our finding of changes in physical function in the absence of changes in performance suggests rupture of the kinetic chain of normal throwing in these subjects.