Three-dimensional kinematic analysis of glenohumeral, scapular, and thoracic angles at maximum shoulder external rotation associated with baseball shadow pitching: comparison with normal pitching

[Purpose] The glenohumeral, scapular, and thoracic angles at maximum shoulder external rotation during shadow pitching were evaluated and compared with those observed during normal pitching. [Participants and Methods] Our study included 13 healthy males with experience in pitcher activity. All participants performed both, shadow pitching using a towel and normal pitching using a ball. The external rotation of the glenohumeral joint, scapular posterior tilting, and thoracic extension angles in the cocking phase were measured using a 3-dimensional motion analysis system. The ratios of the glenohumeral external rotation angle to the scapular posterior tilting and/or thoracic extension angle were calculated to evaluate the contribution of the scapulothoracic joint at maximum external rotation during throwing/pitching activity. [Results] The glenohumeral external rotation angle at maximum shoulder external rotation was significantly smaller during shadow pitching than during normal pitching. The ratio of the glenohumeral external rotation angle to the scapular posterior tilting and/or thoracic extension angle showed no statistically significant difference. [Conclusion] We conclude that shadow pitching can reduce the external rotation motion of the glenohumeral joint compared to that during normal pitching and might be a useful pre-throwing program beneficial in the rehabilitation of those presenting with throwing injuries.