The Importance of Assessing Shoulder Range of Motion in Baseball and Throwing Athletes

In baseball and other throwing sports, shoulder health is paramount for athletes' performance and injury prevention. The repetitive motion of throwing places significant stress on the shoulder joint, making it crucial to monitor shoulder range of motion (ROM) as a predictor of potential injury for shoulder and elbow injuries. Two key metrics used in assessing shoulder ROM are Glenohumeral Internal Rotation Deficit (GIRD) and Total Range of Motion (TROM). Understanding these measurements can help identify athletes at risk for shoulder and elbow injuries, enabling preventative measures to be taken.

Glenohumeral Internal Rotation Deficit (GIRD)

GIRD refers to a loss of internal rotation in the throwing shoulder compared to the non-throwing shoulder. First off, it is NORMAL for throwers to have greater external rotation and less internal rotation in their throwing shoulder compared to non-throwing shoulder due to bony adaptations that occur (humeral retroversion). Other potential causes of less internal rotation can be capsular changes, soft tissue restrictions and scapular position. However, when this loss becomes excessive, it can increase the risk of injury.

A high level of GIRD (> 20 degrees deficit) is associated with altered shoulder mechanics, which can place additional stress on the shoulder and elbow. If an athlete has more than a 20-degree difference in internal rotation between their throwing and non-throwing shoulder, they are considered to have clinically significant GIRD. This condition can increase the likelihood of shoulder injuries such as rotator cuff tears, labral injuries, and impingement. It can also contribute to elbow issues like UCL (ulnar collateral ligament) injuries, as the altered shoulder mechanics may change the forces experienced by the elbow during throwing.

Total Range of Motion (TROM)

TROM refers to the sum of internal and external rotation of the shoulder. In a healthy throwing shoulder, the total range of motion should be relatively symmetrical between the throwing and non-throwing sides, even if the specific internal and external rotations differ. For example, the throwing shoulder may have more external rotation but less internal rotation, while still maintaining a similar overall TROM compared to the non-throwing shoulder.

Monitoring TROM is crucial because a deficit of greater than 5 degrees on the throwing side compared to non-throwing side can indicate restricted shoulder movement, which could predispose an athlete to injury. If the TROM on the throwing side is significantly less than that of the non-throwing side, it suggests that adaptations in the shoulder have exceeded normal limits, potentially leading to compensatory movement patterns that increase the risk of both shoulder and elbow injuries. Maintaining balanced TROM helps ensure that the shoulder joint functions efficiently throughout the entire throwing motion.

Why Assessing GIRD and TROM Matters

Assessing GIRD and TROM provides valuable insights into a throwing athlete's shoulder health and can help guide injury prevention and rehabilitation programs. Identifying a significant internal rotation deficit or a reduced TROM can prompt early interventions, such as targeted stretching, strengthening exercises, or manual therapy to restore proper shoulder mechanics. For instance, addressing GIRD through posterior capsule stretching, scapular strengthening and/or rotator cuff strengthening can help improve shoulder internal rotation and reduce injury risk. Similarly, maintaining balanced TROM supports efficient shoulder movement and minimizes compensatory stresses on the elbow.

By regularly assessing shoulder range of motion, coaches and healthcare professionals can better monitor throwing athletes for early signs of shoulder dysfunction, implement preventive strategies, and ultimately reduce the incidence of shoulder and elbow injuries in baseball and other throwing sports.