Shoulder Rotation Laxity is Related to Pitching Mechanics

According to the 2002 Major League Baseball Disability Analysis, almost 70% of players on the disabled list are pitchers and throwing arm related injuries account for 53% of all disabled list placements. To reach a high ball speed, pitchers cock, or excessively externally rotate their pitching arm to or near an extreme ROM of 180° [1]. The shoulder is then immediately internally rotated to an astonishing 7000°/s after the leading foot contact. The excessive external rotation ROM and astonishing internal rotation velocity are thought to contribute to injury [2]. Repeated exposure to the excessive ROM and large shoulder loads may cause excessive laxity to the anterior shoulder and/or damage the soft tissue [2]. This can lead to shoulder instability and excessive humeral head translation that may cause impingement [3]. Therefore, the mobility and stability of the thrower’s shoulder are extremely relevant to performance and injury prevention.