Changes in Shoulder Rotation for Elite Baseball Pitchers

Do professional baseball players have greater motion in their pitching arm? . Throwing athletes often have shoulder overuse injuries. This study was done to compare shoulder motion and stiffness in the pitching arm compared to the nonthrowing shoulder. The researchers expected the stresses of long-term throwing to change shoulder motion.

Thirty-four professional baseball pitchers joined the study. Range of motion (ROM) and stiffness were measured using two different methods. They found the pitching shoulder had more outward (external) rotation and less inward (internal rotation) when compared to the other side.

Greater external rotation can be explained by the arc of motion needed for throwing. The pitcher begins in a position of extreme external rotation before releasing the ball forward. According to the results of this study, the total arc of rotation was unchanged. Total motion was the same from side to side but there was a shift in where the rotation occurred from one side to the other.

The front of the shoulder was more lax than the back half. The soft tissues, ligaments, and joint capsule may stretch out in the front from the constant position of external rotation. Measuring stiffness of the shoulders showed no overall difference in passive stiffness from side to side. The authors say the results of this study show that overuse of the throwing arm doesn't lead to an unstable joint.