Twist can harm an arm

Staff WriterMay 15, 2011 

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An ongoing study by Dr. Joseph Myers of the University of North Carolina indicates constant, repetitive throwing may alter the shape of young athletes' arms, possibly increasing the likelihood of injury.

Myers' study has revealed that many high school baseball players have twisted their humerus bone, which connects the lower arm and the shoulder, probably through the constant motion of throwing. The twist makes throwing a baseball or softball more efficient.

Myers emphasizes that until the study is complete it is not known whether the twist is good or bad, but the added twist appears to be a factor in the increase of elbow injuries. "It is worrisome," Myers said.

The study is the first to assess athletes, who later are injured, before they are injured.

The goal is to find a way to identify baseball players who are most susceptible to throwing injuries. If athletic trainers could identify the players most likely to have throwing injuries, the trainers hope they could prevent the injuries by using an exercise program specific to that athlete.

The UNC study involves 650 baseball players at 26 high schools throughout the state. This spring and last, before the start of baseball season, Myers and his researchers checked the upper body strength, flexibility and bone structure of the high school baseball players participating in the study.

The results from those measurements are cross-checked later with players having arm and shoulder injuries. The three-year study seeks to establish a link between injury and physical characteristics such as flexibility, strength and bone structure.

"If we had an indication of who was most susceptible to hurting their arm, maybe we could do something to prevent the injury from ever occurring," said Aaron Minger, a certified athletic trainer at Brougton High.

The humerus has a natural slight twist from shoulder to elbow. In most people, there is a difference of approximately five degrees in the bone twist between their dominant arm (right side for right-handed people) and their other arm. The difference is caused by greater use of the dominant hand in the daily routine.

Using ultrasound technology, Myers has learned the difference between high school baseball players' arms is sometimes as much as 15 to 20 degrees.

"The body adapts," Myers said. "The twist in the bone is actually beneficial to throwing a ball, but the data so indicates that the greater the difference between the twist of the dominant arm from the other arm, the more likely there will be an arm problem."

Myers suspects the change in the humerus may begin in players in their early teens. He hopes exercises can be developed to protect athletes who appear to be most at risk.

Myers said he doesn't expect his study to change the sports culture in the United States, but might limit the damage caused by the system.

"Children will probably continue to play too much, specialize too soon and throw entirely too much," he said. "But hopefully, we'll prevent some injuries.

"If we can project who is likely to be injured, maybe we can find ways to keep the injury from ever occurring."

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