Scher S et al.  Associations among hip and shoulder range of motion and shoulder injury in professional baseball players.  J Athl Train. 2010;45(2):19-197.

The Down Low:  According to this study, pitchers with a history of shoulder injury had decreased hip extension on the throwing side coupled with increased shoulder external rotation of the throwing shoulder.  In other words, if the dominant (throwing side) leg is lacking hip extension flexibility, the body will compensate by increasing the shoulder external rotation to create the “whiplike” effect.  This places more stress on the front of the shoulder (and elbow), potentially causing SLAP tears, rotator cuff tears, and ulnar collateral ligament tears in the elbow (Tommy John).

Take Home Message:   Train the entire body… throwing is not just about the shoulder.  Work on dominant side hip extension flexibility (ie. 1/2 kneeling stretch) and lead leg strength and hip stability.  Incorporating trunk control / core stabilization is equally important.