A tool that we’ve become fond of around the facility is The Rotater. The vast majority of older baseball pitchers exhibit glenohumeral internal rotation deficit (GIRD), as outlined by any number of research papers, including the aptly-named Glenohumeral internal rotation deficit in the asymptomatic professional pitcher and its relationship to humeral retroversion (PDF link). GIRD is associated with the dominant throwing shoulder of the baseball athlete, where external rotation is significantly and drastically higher than the degrees of external rotation in the non-dominant (glove arm) shoulder. This isn’t necessarily a problem that needs to be restored to equality, as humeral retroversion (the twist of the humerus in the throwing arm) along with other osseous changes happen as a result of stressors placed on the throwing arm during pitching/throwing that could be beneficial overall.
Baseball is an asymmetrical sport, and any hopes of restoring both sides to equal ER and IR are misguided at best. We don’t throw with both arms, so the dream of stabilizing ER is simply not going to happen. However, stabilizing total motion between the shoulders can have immense benefit. For more on that, you can check out Eric Cressey’s excellent Optimal Shoulder Performance DVD set:
Improving Dominant Shoulder Internal Rotation
A generic stretch that people can do (and that we like) is the side-lying sleeper stretch for the dominant shoulder.
We also love The Rotater for improving IR in the throwing shoulder. Jack demonstrates how he uses it for IR purposes, as shot put athletes have similar demands on their shoulders (and rapid elbow extension with heavier implements):
Often, we’ll use The Rotater for gently stretching the throwing shoulder into ER before throwing a bullpen, or using it more aggressively to stretch out the non-dominant shoulder to help restore total motion between both shoulders.
I’ve had the tool for a few months now and have been holding off on reviewing it until I was satisfied that it both did the job and that it was durable enough to keep around. As a guy who generally prefers DIY equipment and used stuff off Craigslist, it takes a lot for more to recommend brand new stuff, but this tool definitely fits the bill. It also helps that Chris and the guys who run the company are stand-up people who really believe in their product and the customer service behind it.