Background: Injuries are common in professional football, especially during matches, and they cause suffering for players, in both the short and the long term. It is therefore important to try to prevent these injuries. One of the most important steps in injury prevention is to fully understand the different risk factors that contribute to these injuries.

Aim: The aim of this thesis was therefore to investigate several match-related factors that have been suggested to be important for the risk of sustaining injuries during professional football matches.

Methods: The thesis consists of four papers, and all analyses are based on data gathered during a large-scale prospective cohort study that has been running since 2001: the UEFA Elite Club Injury Study. Medical teams from 61 clubs have been involved in this study, and they have prospectively gathered data about football exposure and injuries for their first team players.

Associations between the following factors and injuries have been analysed: • Match characteristics in terms of match venue, match result, and competition • Match congestion, both short and long term, and at team and individual player level • Number of completed training sessions between return to sport after an injury and the first match exposure

Results: All match characteristics studied were shown to be associated with injury rates, with higher injury rates during home matches compared with away matches, in matches that were lost or drawn compared with matches won, and in domestic league and Champions League matches compared with Europa League and other cup matches. It was also shown that injury rates, muscle injury rates in particular, were higher if the recovery time between matches was short. This association between match congestion and injury rates was shown when match congestion was considered at both team and individual player level. Finally, the odds of injury during the first match exposure after a period of absence due to injury was found to be higher if players had completed few training sessions between return to sport and their first match.

Conclusion: There are several match-related risk factors that contribute to the injury rate during professional football matches. A better understanding of these risk factors will help teams to make better estimations of the injury risks to which players are exposed in different situations (e.g. during periods of match congestion and when players return to sport after an injury). Knowledge about risk factors will also offer the possibility of reducing the number of injuries for football teams by addressing them with appropriate measures.