Tommy John Surgery’s Impact on Pitch Load Values in Major League Baseball Players

Introduction: Pitch load (PL) is an alternative to conventional baseball metrics. It may also better monitor overtraining and injury risk. PL is the summation of the product of pitch types thrown multiplied by their respective velocities over a single game or season. This study examined whether PL is impacted by ulnar collateral ligament (UCL) damage, which is treated with Tommy John surgery.   Methods: With publicly accessible retrospective data from 222 MLB pitchers, UCL damage’s influence was assessed. PL was calculated with an expanded formula that is the summation of all pitch types thrown, as well as individual formulas per pitch type (fastball, breaking ball, off-speed) examined. In addition, pitch velocity and distribution, two more traditional baseball metrics, were calculated and analyzed. Each pitcher’s calculated PL for their first available complete (>100 pitches) season before and after surgery were collected and analyzed. Data analysis entailed paired t-tests, with an a < 0.05 denoting significance. Results: There were no pre- to post-surgery changes to pitch distribution, but significant losses to fastball and breaking ball velocities. In contrast, PL values declined significantly for the expanded formula (pre: 113,470 ± 82,577, post: 62,045 ± 56,902, p < 0.001), as well as those per pitch type. Conclusions: Compared to pitch velocity and distribution, PL demonstrates a greater sensitivity and precision to Tommy John surgery. Results imply PL may better serve MLB pitchers as a metric to monitor overtraining, injury risk, and perhaps a tool to construct return-to-play guidelines after Tommy John surgery.