How many innings can we throw: does workload influence injury risk in Major League Baseball? An analysis of professional starting pitchers between 2010 and 2015

Background: There has been increasing interest regarding the association between pitch counts, as well as total workload per season, and the risk of injury among Major League Baseball (MLB) starting pitchers.

Methods: We used publicly available databases to identify all MLB starting pitchers eligible for play who made at least 5 starts in seasons between 2010 and 2015. For all included pitchers, annual pitching statistics (number of starts, total season pitch counts, total season inning counts, and average pitch count per game started) and annual disabled list (DL) information (time on DL for any reason and time on DL related to upper extremity, lower extremity, or axial body injury) were collected. A multiple logistic regression analyzed games started, pitch counts, innings pitched, and pitches per start during all previous seasons as a risk factor for injury in the current season, controlling for previous injury.

Results: A total of 161 starting MLB pitchers met the inclusion criteria. With the exception of total innings pitched from 2010-2011 being significantly associated with DL placement in 2012 (no DL, 310.5 ± 97.5 innings; DL, 344.7 ± 85.9 innings; P = .040), no other finding for starts, pitch counts, innings, or pitches per start in the cumulative years from 2010-2014 had a significant association with pitcher placement on the DL for any musculoskeletal reason or for an upper extremity reason between 2011 and 2015.

Conclusions: In this study, we demonstrate that there is no association between preceding years of cumulative pitches, starts, innings pitched, or average pitches per start and being placed on the DL for any musculoskeletal reason.