It is very common, in fact it is the norm, for pitchers to have an increased external rotation in their pitching shoulder (see above). Years ago many pitchers would try to gain more external rotation by stretching their shoulder. However, this was only helpful while baseball was a one season per year sport. The amateur pitchers would play other sports and the pros would actually hold real jobs in the off-season! Their shoulders would tighten up during the months of not throwing. Now most competitive throwers play baseball year-round and maintain their range of motion (ROM) by throwing. A much more common scenario is that the thrower will lose internal rotation. There a few reasons why.
As a child throws, the bones around the shoulder are under great stress. A childs bones will change shape or in response to this stress and result in a gradual increase in external rotation and loss of internal rotation. This has been documented in some recent studies in the
A second reason, however, is not permanent. The stress of repetitive throwing also generates changes in the muscles, ligaments, tendons, and capsule(the soft tissues) of the shoulder. As mentioned in the Throwing Overview, the shoulder will stretch and become looser to allow more ER. But, at the same time, the soft tissues in the back (posterior) of the shoulder will tighten. This causes a loss of IR. It has been shown that this loss of IR predisposes throwers to shoulder injuries such as labral tears and rotator cuff tears. The good news is that this problem is correctible without surgery.
In 2004 we evaluated the shoulders of every pitcher in Spring Training with the Houston Astros Baseball Club, including Major and Minor Leaguers. About ten years a go, David LaBossiere ATC, the Astro's Head Athletic Trainer noticed this loss of IR, and developed what was a novel approach at that time. He began stretching the pitchers shoulders in IR, avoiding any attempt to increase ER. This paid great dividends: the Ballclubs injury rate decreased and for years the Astros have had one of the lowest injury rates in the Major Leagues. More and more Clubs are now doing similar programs. Our study showed that pitchers who were new to the stretching program lacked IR, but that the longer they were in the program the more IR they regained, eventually returning to normal. This study was presented at the Annual Meeting of the Major League Baseball Team Physicians Association and proved that a consistently-applied stretching program will correct the loss of internal rotation without loss of external rotation. In other words, a pitcher can gain the ER he needs to throw hard without losing the IR that he needs to prevent injury. This study clearly showed that most pitchers coming out of high school and college had not had a consistent stretching program design to minimize their loss of IR, but that this critical motion could be regained. Since this was the first study to show that the previously lost IR could be regained and maintained, we have embarked on an educational program to encourage high school and college programs to include a internal rotation stretching program in their daily routine.