Although baseball is not considered a contact sport, baseball players are still susceptible to a multitude of injuries, in particular shoulder injuries. Injury to the muscles or tendons of the shoulder is known as a rotator cuff injury. Rotator cuff injuries are associated with several epidemiological risk factors that are common among baseball players, which is why this group is so commonly afflicted.
Rotator Cuff Anatomy
Epidemiology is the study of diseases in a certain population and why these diseases occur. To better understand the epidemiology of rotator cuff injuries in baseball players, it is best to first take a look at the anatomy of the shoulder itself. The rotator cuff is comprised of four muscles that surround your shoulder joint: the supraspinatus, infraspinatus, teres minor and subscapularis. Together these muscles function to support your shoulder as well as raise and twist your arm. The rotator cuff muscles attach to your shoulder blade, collarbone and upper arm bone by a type of connective tissue known as tendons. Two types of injuries may affect the rotator cuff: strains and tendinitis. Strains occur when the muscles or tendons are overstretched or even torn. Tendinitis is a condition in which the tendons become irritated and inflamed.
Repetitive Overhead Movements
Baseball players, in particular pitchers, are at an increased risk of developing rotator cuff injuries due to repetitive overhead movements of the arm as well as the sheer force exerted on the rotator cuff from throwing. The rotator cuff is primarily responsible for executing the throwing motion of baseball. In the throwing sequence, the muscles of the rotator cuff endure the greatest amount of force during the late cocking phase and the follow-through phase of a throw. The principle movement of the arm during throwing is internal rotation, which is supplied by the subscapularis. This movement can exert an inordinate amount of stress on the rotator cuff. According to "Complete Conditioning for Baseball" by Steve Tamborra, internal rotation of the arm during a 90-mph pitch is equivalent to a velocity of 6,000 to 10,000 degrees a second.
Rotator Cuff Weakness
Weakness in the muscles of the shoulder may also play a role in epidemiological risk. According to a 2009 study published in the "American Journal of Sports Medicine," baseball players with weakness of the supaspinatus and external rotators had an increased risk of rotator cuff injury. The researchers suggest the implementation of a preseason strength training program may reduce the occurrence of rotator cuff disease.
Other Risk Factors
Other risk factors for rotator cuff disease unrelated to baseball include age greater than 40, improper posture, lifting heavy objects and jobs that involve repetitive overhead movements of the shoulder.
References
- World Health Organization: Epidemiology
- American Academy of Orthopedic Surgeons; Rotator Cuff Tears; October 2007
- Brown University; Mechanisms of Shoulder Injury; Blair Smith, et al.; May 2004
- "Complete Conditioning for Baseball"; Rotator Cuff Heavily Used by Baseball Players; Steve Tamborra
- "American Journal of Sports Medicine"; Preseason Shoulder Strength Measurements in Professional Baseball Pitchers; Dr. Ian R. Byram, et al.; July 2010
- MayoClinic.com: Rotator Cuff Injury; Risk Factors; August 2010
