Throwing motion in young baseball players may actually protect shoulder

Jul 16 2007

Adaptive changes occur in the arm bone and soft tissue of the shoulders of young athletes participating in youth baseball and help protect them against injury, according to new research released at the 2007 Annual Meeting of the American Orthopaedic Society for Sports Medicine at the Telus Convention Center.

"Young baseball players who throw a lot maintain external shoulder rotation as they mature," says principal investigator Scott D. Mair, M.D., associate professor of orthopedic surgery at the University of Kentucky in Lexington. Good external rotation of the shoulder helps athletes throw faster while reducing their chance of injury.

Some shoulder motion is naturally lost through aging. Dr. Mair says that the throwing shoulder does not lose as much external rotation. "An adult will never have as much shoulder motion as a nine year-old," he explains.

To evaluate the adaptive changes in the shoulder joint of overhead throwing athletes, Dr. Mair and colleagues followed 32 male baseball players between 13 and 21 years of age for six years to study changes in range of motion, strength, and X-ray images.

The researchers found that the act of throwing causes changes in the upper arm bone and soft tissue in the shoulders of young baseball players. "This is not necessarily a bad thing," explains Dr. Mair. "It can help protect players from injury. However, pitch counts that are too high and playing year-round can push those adaptive changes to the point of injury."

Parents of young baseball players need not be overly concerned about their children's shoulders. "Throwing is fine as long as it is in moderation and the parents and child use common sense. A 10-year-old pitcher shouldn't be throwing through pain to win a Little League game," concludes Dr. Mair.

Dr. Mair notes that children need a break from throwing: "In the old days kids pitched in the summer and then played basketball or football in the winter. That was better for growing children. Now, some children play baseball 12 months a year. That can be a problem. Shoulder changes that go beyond adaptation can lead to pain and even growth plate injuries.