How does the All-Star break affect injury rates in professional baseball?

Injury rates in professional baseball players are increasing. It is unclear if the time of rest from the All-Star break affects injury risk.

Every professional baseball game (A-, A+, AA, AAA, and Major League Baseball) played between 2011 and 2017 was included. Each game was then classified as control game (games played in April, May, June, and September) or game within one month after the All-Star break. Incidence of injuries in games within one month of the All-Star break was compared with the control games.

Our analysis included 66,642 games: 46,630 control games and 20,012 games played within one month after the All-Star break. On univariate analysis, there was a mean ± standard deviation of 0.45 ± 0.72 injuries per game in control games and 0.41 ± 0.68 injuries per game in games played within one month after the All-Star break (P<.001). On multivariate analysis, there was a significant association between games played within one month after the All-Star break and number of injuries per game (P<.001) after adjusting for the level of play and game duration. However, the effect size was 0.001, suggesting this effect is clinically insignificant.

There does not appear to be a clinically significant difference in injury rates per game in professional baseball players between games played in the month after the All-Star break and all other games played during the season. Although the All-Star break provides most players with a chance to rest, it does not appear to have an effect on injury rates.