Computer Simulation Shows the Importance of Arm Muscles for Baseball Pitchers

By Dan Peterson, TeamSnap's Sports Science Expert

 

Let’s face it. Pitching a baseball dozens of times over two hours is just not a physical activity that our arm anatomy was built to withstand. The stress placed on bones, ligaments and muscles repeatedly has been the cause of many injuries, especially to the elbow’s ulnar collateral ligament (UCL), which often results in a replacement and reconstruction procedure known as Tommy John surgery.

The role of the supporting muscles around the elbow during the pitching motion has not been clear due to a lack of a sophisticated motion analysis system that looks at how bone, ligament and muscle work together to manage the workload. However, a new computer simulation developed by Northwestern University biomedical researchers is providing new evidence of how the stress on the UCL is created during a pitch and better ways to mitigate the damage done.

James Buffi PhD, a researcher at Northwestern’s McCormick School of Engineering and Applied Science, took a different approach by creating a computer model combining geometric measurements similar to an approach used to study advanced prosthetic devices for arms and hands. By understanding how different levels of muscle volume help the bones and ligaments of the elbow, the team can advise players, trainers and physicians on muscle development of young arms.

"Muscles matter in baseball," said James Buffi, first author of the study. "We showed that a pitcher could be at a really high risk or a really low risk of elbow injury, depending on how strong and capable his muscles are."

Their new model, which can be viewed in this video, was developed from an actual high school pitcher’s arm motion.

"Pitching is an extreme and difficult motion," said co-author Wendy M. Murray, associate professor of biomedical engineering at McCormick and a research scientist at the Rehabilitation Institute of Chicago. "Pitchers are literally throwing so hard that the motion itself acts to tear the elbow joint apart. But why doesn't it? The answer is the strength of the muscles and the ligaments. That's what keeps the bones together."

Muscles are the key to arm strength and stability, according to Murray.

"Our simulations illustrate that if the muscles were doing nothing, then the bones that make up the elbow joint could have been pulled apart during that single pitch. In contrast, we also were able to implement reasonable assumptions about muscle performance that showed how the very same pitch could result in no load on the UCL at all," Murray said.

The research has been published in the Annals of Biomedical Engineering.

Even though the model was based on one pitcher’s motion, it allows the research team to create many different scenarios by varying muscle volumes, throwing angles and velocity. Hopefully, this will generate better advice to future pitchers on how to properly prepare their entire arm for better durability.

"Elbow injuries are a huge problem in baseball, from little to major leagues, and our study shows that muscles play a part," Buffi said. "If you're not accounting for muscles, even if you know the total elbow load on a pitcher, he could be at a really high risk or a really low risk of injury depending on how strong and capable his muscles are."