Shoulder model for baseball pitching

• Name: Peter Hordijk 
• Title: Musculoskeletal modeling of the shoulder during baseball pitching: A research combining 3D kinematic measurements with musculoskeletal modeling
• Grade: 7.5

Although not a baseball fan himself, Peter Hordijk was intrigued by the extreme motion of the shoulder during pitching. The shoulder is crucial in transferring the energy from the legs to the hand. Due to the high speed and power of throwing, the arm of a pitcher is subjected to extreme motions. “Many struggle with elbow and shoulder injuries, involving both the joints and the surrounding muscles. This usually leads to a relatively short career, Hordijk explained. He therefore estimated the muscle power and load on the joints, which give an indication of the risk of injury.

Muscle power cannot be directly measured outside of the body. Motion captures, markers on the shoulder area, can record the motion in 3D. The movement is then simulated in the computer using an advanced model of the human shoulder. This yields information about the origin of the movement and allows for an estimation of the muscle power and joint load. “My goal was to find a link between this muscle power or joint load and the motion of the shoulder,” added Hordijk. This link could be the first step towards preventing injuries.

‘You never know when you are finished’

The shoulder model had never been used for pitching movements before. It was designed for simple tasks, not to accommodate high muscle forces and extreme arm positions. Due to the huge range of motion involved in pitching, he was confronted with many challenges in the simulation. “This led to suggestions of changes in the model, to make future pitch simulations better and the results more realistic,” said Hordijk.

While he successfully managed to make realistic estimations of the muscle power and joint load and link this to shoulder motion in the end, the simulation was the hardest part. “There is always room for improvement and you never know when you are finished,” Hordijk said. His tip for other graduate students is therefore to go with the flow and accept that you will not know when you cross the finish line. Hordijk’s project was part of a collaboration with the Dutch baseball association. The ultimate goal is to record the motion in real-time and adjust the pitcher’s training to accomplish a safe and fast pitch.

Annemijd Smid