Game Spacing and Density in Relation to the Risk of Injuries in the National Hockey League

BACKGROUND: Ice hockey has significant workload demands. Research of other sports has suggested that decreased rest between games as well as an increased workload may increase the risk of injuries. PURPOSE: To evaluate whether condensed game schedules increase the frequency and severity of injuries in the National Hockey League (NHL). STUDY DESIGN: Descriptive epidemiology study. METHODS: Data were obtained from publicly available online sources on game schedules and injuries for all NHL teams for the 2005-2006 through 2018-2019 seasons. Injury rates (per team per game) and the proportion of severe and nonsevere injuries were determined. The game-spacing analysis assessed the risk of injuries in relation to the number of days between games played (range, 0-≥6 days). The game-density analysis assessed the risk of injuries in relation to the number of games played within 7 days (range, 1-5 games). Results were assessed by analysis of variance, the post hoc Tukey test, and the chi-square test of distribution. RESULTS: The game-spacing analysis included 33,170 games and 7224 injuries, and a significant group difference was found (P = 1.44×10(–5)), with the post hoc test demonstrating an increased risk of injuries when games were spaced with <1 day of rest. There was no significant difference in the ratio of severe to nonsevere injuries. The game-density analysis included 33,592 games and 10,752 injuries, and a significant group difference was found (P = 8.22×10(–48)), demonstrating an increased risk of injuries with an increased number of games in all conditions except for the comparison between 4 versus 5 games in 7 days. There was also a significant difference in injury severity (P = .008), indicating that the least dense condition had a higher ratio of severe to nonsevere injuries compared with the other game-density conditions. Finally, the game-density analysis was repeated after excluding games played with <1 day of rest, and the finding of increased injury rates with increasingly condensed schedules remained significant (P = 9.52×10(–46)), with significant differences between all groups except for the comparison between 1 versus 2 games in 7 days. CONCLUSION: We found that a condensed schedule and <1 day of rest between games were associated with an increased rate of injuries in the NHL. These findings may help in the design of future game schedules.