Injury rates in team sport events: Tackling challenges in assessing exposure time

Recording exact amounts of exposure time in sport events is overly cumbersome for many sports injury surveillance projects. When individual-level data are unavailable, sports injury epidemiologists currently use one of two main methods to assess overall exposure time. The AAR method includes only the number of athletes at risk on the field during the respective sporting events. This method closely replicates the results of the individual-level exposure time calculations if studies have full team enrolment and games are played with a consistent number of players. In contrast, the AP method applies a full unit of exposure time to everyone who plays in a game, however briefly, or to everyone on the game roster whether they participate or not. Consequently, the AP method underestimates game injury rates (because it overestimates exposure time) with a magnitude related to the proportion of players on the field (ie, those at risk) divided by the number of players on the team who are considered to have participated. Recognising this is necessary to properly assess risk factors for injuries in team sport events, appropriately target injury prevention efforts and accurately combine studies using different methods in systematic reviews or meta-analyses.