MONDAY, July 16, 2007 (HealthDay News) -- Repeated pitching changes the dynamics of movement in a young man's arm, according to research that shows that regularly throwing a baseball hampers one kind of motion, while boosting another.
These changes in throwing arm flexibility are "not necessarily a bad thing and may actually allow better velocity and less injury," said study principal investigator Scott D. Mair, associate professor of orthopedic surgery at the University of Kentucky in Lexington.
However, when pitchers overdo it, he said, pain can result.
At issue is the ability of the arm, and the shoulder in particular, to withstand repeatedly throwing a baseball. Young men in particular may be prone to injury, because some play the game year-round, and because the bones and muscles in their arms are still growing and changing.
In the new study, conducted in 2006, doctors examined the arms of 32 male baseball pitchers, averaging 18 years of age, six years after an initial examination. Radiologists also took X-rays of the pitchers' shoulders.
Mair's team found that the pitchers actually gained what is called "external rotation" -- "with your arm straight out to the side, you can rotate it back further like you were cocking to pitch," Mair said. That's a good thing, and it might even protect the shoulder from injury.
However, the young players also lost range of motion in what's called "internal rotation" (moving the arm in the opposite direction, as in letting a pitch go).
The latter "is a permanent change that you can find in virtually anyone who threw a lot as a kid," Mair said. "It does not seem to result in any permanent significant effects on life outside of throwing."
It was also normal for the pitchers to lose some external rotation in the non-throwing arm over time as they grew.
The findings were to have been presented Sunday at the 2007 annual meeting of the American Orthopaedic Society for Sports Medicine, in Calgary, Alberta, Canada.
According to Mair, better flexibility is a very good thing for the pitchers to develop and not just to lower their earned-run average: "External rotation is important in throwers and pitchers in generating velocity and may protect (the arm) from injury," he said.
Malachy McHugh, director of research at the Nicholas Institute of Sports Medicine and Athletic Trauma at Lenox Hill Hospital in New York City, said the movements involved in throwing a ball appear to have different effects on flexibility. "The loss of internal rotation is probably related to deceleration after you release the ball. And the increase in external rotation is from repetitively moving your arm," he explained.
Injuries occur when the loss of internal rotation becomes too great, McHugh said, adding that stretching is one way to help young pitchers cut this loss of internal rotation. And, of course, pitchers should avoid playing too much.
What's next? According to Mair, there's "still a lot of work to be done in finding out how the growth plate responds to throwing, how to keep kids from being injured, determining pitch counts and days of rest needed, and in educating kids, parents and coaches."
More information
Learn more about baseball safety at SafeUSA.org.
