Fastball Velocity and Elbow-Varus Torque in Professional Baseball Pitchers

Abstract

Context: High loads in the elbow during baseball pitching can lead to serious injuries, including injuries to the ulnar collateral ligament. These injuries have substantial implications for individual pitchers and their teams, especially at the professional level of competition. With a trend toward increased ball velocity in professional baseball, controversy still exists regarding the strength of the relationship between ball velocity and elbow-varus torque.

Objective: To examine the relationship between fastball velocity and elbow-varus torque in professional pitchers using between- and within-subjects statistical analyses.

Design: Cross-sectional study.

Setting: Motion-analysis laboratory.

Patients or other participants: Using the previously collected biomechanical data of 452 professional baseball pitchers, we performed a retrospective analysis of the 64 pitchers (52 right-hand dominant, 12 left-hand dominant; age = 21.8 ± 2.0 years, height = 1.90 ± 0.05 m, mass = 94.6 ± 7.8 kg) with fastball velocity distributions that enabled between- and within-subjects statistical analyses.

Main outcome measure(s): We measured ball velocity using a radar gun and 3-dimensional motion data using a 12-camera automated motion-capture system sampling at 240 Hz. We calculated elbow-varus torque using inverse-dynamics techniques and then analyzed the relationship between ball velocity and elbow torque using both a simple linear regression model and a mixed linear model with random intercepts.

Results: The between-subjects analyses displayed a weak positive association between ball velocity and elbow-varus torque (R² = 0.076, P = .03). The within-subjects analyses showed a considerably stronger positive association (R² = 0.957, P < .001).

Conclusions: When comparing 2 professional baseball pitchers, higher velocity may not necessarily indicate higher elbow-varus torque due to the confounding effects of pitcher-specific differences (eg, detailed anthropometrics and pitching mechanics). However, within an individual pitcher, higher ball velocity was strongly associated with higher elbow-varus torque.

Keywords: Tommy John surgery; biomechanics; pitching; throwing; ulnar collateral ligament.

Figure 1

Plot of normalized maximum elbow-varus torque versus ball velocity. Each pitcher is represented by a series of points and the best-fit line in one color, whereas the regression line from the linear mixed model is represented by the thick black line. This model suggested a strong positive relationship between varus torque and velocity (R² = 0.957).

Figure 2

Plots of pitching performance metrics versus average fastball velocity for 2015–2017 Major League Baseball pitchers who qualified for the earned-run-average (ERA) title, including simple linear-regression best-fit lines. A, ERA. B, Walks plus hits per inning pitched (WHIP). C, Fangraphs wins above replacement (fWAR; https://www.fangraphs.com/). D, Baseball Reference wins above replacement (bWAR; https://www.baseball-reference.com/). All metrics showed associations with velocity (P < .05), but the coefficient of determination (R²) values were low. Whereas commonly used in the baseball community to assess player performance, wins above replacement does not have 1 standardized formula. This Figure includes plots for the 2 most widely accepted versions: from Fangraphs and Baseball Reference. Data for average fastball velocity, ERA, and WHIP were also obtained from the Fangraphs Web site.