Shoulder kinetic during pitching in baseball players with scapular dyskinesis

Introduction: Shoulder injuries in baseball players cause excessive shoulder load during pitching and scapular dyskinesis (SD). However, the characteristics of pitching kinetics in the shoulder joint with SD are unclear. This study aimed to investigate the effect of SD on pitching kinetics in the shoulder joint of baseball players. Method: Seventy-two college and independent league baseball players participated in the study. The pitching motion was measured using an 18-camera motion-capture system. SD was classified into four types (I-IV) using the scapular dyskinesis test (SDT). The pitching kinetics data were analyzed. Results: The agreement of SD in this study was 56/72 (77.8%). SD were classified into 31 abnormal group (type I-III) and 25 control group (type IV). Three participants with measurement failure during the pitching motion analysis were excluded from the analysis. The abnormal group showed a larger maximum value of the gleno-humeral normalized anterior joint force than the control group. Conclusions: These results suggest that an increase in GH anterior force during pitching causes an excessive in-crease in external rotation of the GH with an insufficient posterior tilt of the scapula with SD. Therefore, baseball pitching with SD may involve shoulder injuries owing to excessive shoulder load during pitching.