A new 3D motion detection system could help identify baseball pitchers who are at risk for shoulder injuries, according to a new study conducted at Loyola University. The system can be used on the field and requires only a laptop computer. Other systems that evaluate pitchers’ throwing motions require cameras and other equipment and generally are confined to indoor use.

In a well-rested pitcher, the humerus (upper arm bone) and the scapula (shoulder blade) move in concert – when one bone moves, the other moves with it. This is called the scapulo-humeral rhythm. But after a pitcher has been on the mound for a while, the muscles begin to tire, and the scapulo-humeral rhythm begins to deteriorate. The bones no longer move in sync, and this can lead to shoulder injuries.

Using just the naked eye, it is extremely difficult for a coach to detect subtle changes in a pitcher’s scapulo-humeral rhythm. But such changes can be easily detected with a portable tracking system called the Xbus Kit®. Sensing units are positioned on the pitcher’s scapula, humerus, forearm and sternum, and information is gathered from 3D gyroscopes, 3D magnetometers, and 3D accelerometers.

Researchers enrolled 13 college pitchers in the study. For each pitcher, the system tracked the scapulo-humeral rhythm three times: Before pitching, after throwing 60 pitches and 24 hours after a pitching session. Only two pitchers showed similar measurement at all three sessions. Five pitchers showed deterioration in the scapulo-humeral rhythm after pitching, but the rhythm was completely restored at 24 hours. Three pitchers showed deterioration after pitching. After 24 hours’ rest, their scapulo-humeral rhythm was improved, but still not completely restored. Three pitchers showed deterioration in the scapulo-humeral rhythm after pitching, and the deterioration persisted even after 24 hours.

The study demonstrates the feasibility of using the portable tracking system to identify college-age pitchers who are at risk for shoulder injuries.

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