Pitch Velocity Best Predictor of Elbow Valgus Torque

Pitch velocity is the predictive factor that most influences elbow valgus toque and shoulder distraction force in pitching arm kinetics, according to a new study.

The authors of “Machine Learning and Statistical Prediction of Pitching Arm Kinetics,” wrote, “Over the past decade, research has attempted to elucidate the cause of throwing-related injuries in the baseball athlete. However, when considering the entire kinetic chain, full body mechanics, and pitching cycle sequencing, there are hundreds of variables that could influence throwing arm health, and there is a lack of quality investigations evaluating the relationship and influence of multiple variables on arm stress.”

For the study that was published online November 15, 2021, in The American Journal of Sports Medicine, researchers wanted to identify the variables that have the most influence on elbow valgus torque and shoulder distraction force using a machine learning approach.

The retrospective review included baseball pitchers who underwent biomechanical evaluation at an university biomechanics laboratory. The researchers created regression models and 4 machine learning models for both elbow valgus torque and shoulder distraction force. They all used the same predictor variable including pitch velocity and 17 pitching mechanics.

Included in the analysis were 168 high school and college pitchers with a mean age of 16.7 years (SD, 3.2 years) and BMI [body mass index] of 24.4 (SD, 1.2).

For both elbow valgus torque and shoulder distraction force, the gradient boosting machine models demonstrated the most precise calibrations compared to the other models.

The one for elbow valgus torque showed that pitch velocity had the highest influence with five mechanical variables also having significant influence. The model for shoulder distraction force also showed that pitch velocity had the highest influence. Six mechanical variables also had significant influence in this model.

While pitch velocity was the most influential model in both models, the authors wrote that pitching mechanics including maximum humeral rotation velocity, shoulder abduction at foot strike and maximum humeral rotation were also of significant influence.

“The results of this study can be used to inform players, coaches, and clinicians on specific mechanical variables that may be optimized to mitigate elbow or shoulder stress that could lead to throwing-related injury,” they wrote.

The authors of the study included Kristen F. Nicholson, Ph.D., Brian R. Waterman, M.D. and Garrett S. Bullock, P.T., D.P.T. of Wake Forest School of Medicine in Winston-Salem, North Carolina and Gary S. Collins, Ph.D. of Oxford University in Oxford, United Kingdom.