Background: Previous studies have demonstrated increased external rotation and decreased internal rotation range of motion in the dominant shoulders of baseball pitchers compared to their non-dominant arms. Recent research has demonstrated that these changes may be the result of an osseous adaptation in the form of proximal humeral retroversion. The purpose of this study was to investigate shoulder flexibility patterns in high school baseball pitchers and possible correlations to fastball velocity and pitching experience.
Methods: Thirty-nine high school baseball pitchers were examined. Dominant and non-dominant shoulder external rotation and internal rotation ranges of motion were measured in 90° of abduction using a standard inclinometer. Fastball velocity was measured using a JUGS radar gun.
Results: Mean external rotation in the dominant arms (121.85°, SD 11.43°) was significantly greater than that found in the nondominant arms (111.54°, SD 11.56°) (p = .0002). In contrast, mean internal rotation on the dominant side (73.00°, SD 12.91°) was significantly less than that exhibited on the non-dominant side (81.74°, SD 14.77°) (p = .0051). The mean total arc of motion (external + internal rotation) between dominant (194.36°, SD 15.72°) and non-dominant arms (193.64°, SD 14.77°) was not significantly different (p = .84). No correlation was found between dominant shoulder external rotation and fastball velocity or years of pitching experience. Discussion and Conclusion: The high school baseball pitchers in this study demonstrated a pattern of increased external rotation and decreased internal rotation in their dominant shoulders compared to their non-dominant shoulders, but the total arcs of motion were symmetrical. These flexibility patterns may be indicative of the osseous adaptation of proximal humeral retroversion and may not necessarily represent pathological changes in soft tissue structures about the shoulder complex as has been previously postulated.
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