Is workload associated with latissimus dorsi and teres major tears in professional baseball pitchers? An analysis of days of rest, innings pitched, and batters faced

Abstract

Background: Latissimus dorsi (LD) and teres major (TM) tears have become increasingly recognized injuries in professional baseball pitchers. The purpose of this study was to determine whether workload, as measured by the number of days of rest between outings, number of innings pitched, number of batters faced, and being a starting pitcher, is associated with an increased risk of sustaining an LD-TM tear in professional baseball pitchers.

Methods: All professional baseball pitchers who sustained an LD-TM tear between 2011 and 2017 were identified using the Major League Baseball Health and Injury Tracking System. A separate player-usage data set was used to determine workload. We then compared workload variables between pitcher-games 2, 6, 12, and >12 weeks prior to a documented LD-TM tear and pitcher-games from a non-LD-TM tear control group. In a paired analysis, we compared the acute workload (2, 6, and 12 weeks) prior to injury and the injured pitchers' non-acute workload >12 weeks prior to injury.

Results: A total of 224 unique LD-TM tears were documented in the Major League Baseball Health and Injury Tracking System database. In most periods, player-games with more innings pitched and more batters faced were associated with a higher incidence of subsequent LD-TM tears. The number of days of rest was not a significant predictor of an LD-TM tear in the acute workload setting, but pitchers who sustained an LD-TM injury averaged fewer days of rest over the previous ≥12 weeks than controls (P < .001). Pitchers who faced >30 batters per game showed a 1.57-fold increase in the percentage of pitchers with a subsequent LD-TM tear as compared with pitchers who faced ≤5 batters per game. Significantly more starting pitchers were in the case group that sustained LD-TM tears over multiple time points than in the control group.

Conclusion: Having a greater pitcher workload and being a starting pitcher were associated with an increased risk of sustaining LD-TM tears in professional baseball players. The average number of days of rest was only a risk factor for LD-TM tears over a 3-month or longer period.

Keywords: Major League Baseball; Workload; injury; latissimus dorsi; pitcher; teres major.