Because shoulder injuries in throwing athletes are so common, it is not surprising that there is a wealth of research on how the way an athlete throws (pitching mechanics) and what happens to the shoulder during the throwing motion (pitching dynamics) affects injury risk.
One recent study, for instance, found that the risk of shoulder injury increased substantially where there was a greater than 25 degree difference in internal rotation between throwing and non-throwing shoulders.
Internal rotation? 25 degrees? What that mean in practical terms to a young pitcher, and to you as a parent trying to reduce the risk of a shoulder injury?
To make sense of the research, there are three basic concepts to understand:
- As a pitcher's arm rotates back (cocking phase), the humeral head (shoulder joint) slides forward. During the throwing (acceleration) phase, the humeral head does the opposite, sliding backwards.
- Over the course of thousands of pitches, this sliding forward and backward will lead to changes in other parts of the shoulder, including making the front of the shoulder more lax or loose and the back of the shoulder tighter.
- The shoulder joint will continue to try to push forward with each throw, increasing the risk of impingement to the rotator cuff and biceps tendon and overall risk of injury.
The research suggests that if there is a significant lack of forward rotation in the shoulder joint, then the risk of injury is increased. It is therefore very important to take steps to ensure the relationship between forward and backward rotation stays balanced.
Screening test
Here's how to test for balance:
- Have the athlete stand with both arms at 90 degrees from his body and elevated to shoulder height (so it looks like both arms are about to throw a ball) with the elbow bent to 90 degrees.
- Have him actively rotate both shoulders backward.
- Then, from the same position, have the athlete rotate both shoulders forward, like throwing a ball.
- If the throwing shoulder reaches way past the opposite arm but, then when rotating forward, there is a large difference in range of motion and the pitcher says "it is really tight" or "it won't move anymore", more stretching is in their future (see below). If there is no big difference, then nothing to worry about.
Easy shoulder stretch
To maintain balance, here's an easy exercise to stretch the shoulder:
- Squeeze shoulder blades together
- Grasp the back of the elbow, bend it at a 90 degree angle, and bring forward while keeping the shoulder blades squeezed together;
- Once some tightness is felt in the back of the shoulder joint, hold for 30-40 seconds. This area can be very, very tight so more stretching may be necessary (3-4 reps) to ensure success.
- Make sure to only complete this stretch (multiple reps, holding for 30-40 seconds) AFTER pitching. Doing a significant stretch BEFORE pitching may alter the joint mechanics too much prior to throwing.
Keith Cronin is a physical therapist in the St. Louis area and a frequent contributor to MomsTeam.
Posted October 25, 2011
