Pitch Types and Their Influence on Elbow Varus Torque and Spin Rate in Professional Baseball Pitchers

Background: Elbow injuries are prevalent among professional baseball pitchers as nearly 25% undergo ulnar collateral ligament reconstruction. Pitch type, ball velocity, and spin rate have been previously hypothesized to influence elbow varus torque and subsequent risk of injury, but existing research is inconclusive. Purpose: To examine elbow varus torque, cumulative torque, and loading rate within professional pitchers throwing fastball, curveball, change-up, and slider pitches, as well as to identify potential influences of ball spin on the elbow. Study Design: Descriptive laboratory study. Methods: A total of 31 professional pitchers (mean height, 189.0 ± 5.7 cm; mean weight, 91.7 ± 8.2 kg) were analyzed using motion capture (480 Hz) and TrackMan while throwing a full bullpen of pitches consisting of fastballs, curveballs, change-ups, and sliders. Elbow varus torque, loading rate, cumulative torque, and spin rate were calculated and analyzed using linear regression to establish within-player and mixed-effects models to establish between-player differences in pitch types. Results: Analyzed by individual pitcher, fastballs exhibited significantly higher mean ball velocity and elbow varus torque (40.4 ± 0.6 m/s; 90.1 ± 3.5 N·m) (all P < .001) and peak elbow varus torque compared with curveballs (33.4 ± 0.6 m/s; 87.5 ± 2.7 N·m), change-ups (36.4 ± 0.6 m/s; 81.3 ± 2.4 N·m), and sliders (36.2 ± 0.7 m/s; 87.7 ± 2.7 N·m). Fastball pitches had a significantly greater cumulative elbow varus torque and loading rate compared to all pitch types within a pitcher ( P < .001). Despite the lower peak elbow varus torque and loading rate, the change-up pitch had the second highest cumulative torque. Curveballs were found to have the lowest cumulative elbow varus torque. No significant relationship was found between spin rates and elbow varus torque across pitch types. Conclusion: Fastballs produced the greatest ball velocity, peak elbow varus torque, loading rate, and cumulative torque among the 4 pitch types analyzed in professional pitchers. Although spin rate has become a popular topic in modern pitching strategies and analyses, this study found no significant relationship between spin rate and elbow varus torque across pitch types, suggesting that spin rate alone may not be a reliable predictor of elbow torque or injury. Clinical Relevance: These findings suggest that pitch type, rather than spin rate, should be considered when assessing risk of elbow injuries in professional pitchers.