Age-related differences in glenohumeral internal rotation deficit, humeral retrotorsion angle, and posterior shoulder tightness in baseball players.

Background: Glenohumeral internal rotation deficit is generally recognized as a risk factor for throwing disability in baseball players. However, the pathology, timing of onset, role in the onset of humeral retrotorsion angle (HTA) and soft tissue extensibility (STE), and the relationship with age remain unclear. Therefore, the purpose of this cross-sectional study was to investigate age-related glenohumeral internal rotation deficit, HTA, and STE in Japanese baseball players and determine whether these factors correlate with throwing disability.