Correlates With History of Injury in Youth and Adolescent Pitchers
Pitching is one of the fastest human motions, with arm internal rotation velocities exceeding 7,000 /s in professional pitchers. These speeds place enormous torques on the shoulder and elbow, regularly exceeding 1,000 N in professional pitchers. These forces reliably produce pain and injury within the shoulder and elbow. Over the course of a single season, over half of all overhand baseball pitchers aged 9 to 14 years will have shoulder and elbow pain, and the incidence of shoulder and elbow injury among pitcher is increasing.
Previous studies at the American Sports Medicine Institute (ASMI) have identified pitch counts and pitching while fatigued; breaking pitches, specifically the curveball and the slider; and lack of rest, specifically pitching on multiple teams or for greater than 9 months per year, as predictors of shoulder and elbow pain in youth and adolescent pitchers. These factors have since been codified into injury-prevention recommendations. Although these studies also performed video pitching analysis on a subset of pitchers within their original cohorts, none of the kinematic factors measured as a portion of the analysis correlated with shoulder or elbow pain during the season.
Laboratory pitching motion-analysis biomechanical data conflict with these findings. Several authors have shown no difference in shoulder and elbow torques between the fastball, the curveball, and the slider. In addition, numerous studies have demonstrated that maximal shoulder external rotation, elbow flexion at ball release, initiation of trunk rotation after front-foot contact, shoulder abduction at foot strike, and elbow flexion at front-foot contact correlate with shoulder and elbow torques. Shoulder and elbow torques predict elbow injury in overhand pitchers.18 It thus follows that kinematic measurements, which can be reliably measured with video motion analysis, should correlate with pain and injury in empirical studies. If kinematic factors that correlate with injury could be identified, then at-risk pitchers could potentially be identified with motion analysis and injuries could be prevented.
We performed a cross-sectional study to determine which demographic and kinematic variables correlate with pitching-related injury. The specific aim of this study was to determine the factors within pitcher demographic characteristics, pitching history, and pitch kinematics, including velocity, that correlate with a history of pitching-related injury. We hypothesized that velocity and kinematic variables such as elbow flexion angle at ball release and maximal shoulder external rotation would serve as the most important correlates of a history of pitcher injury.