Does game-day circadian misalignment or environmental temperature influence team performance in the Australian Football League? An examination of historical data.

OBJECTIVES: Examine Australian Football League results for evidence that game-day circadian misalignment or environmental temperature influence games with competing teams from each of Western Australia and Victoria. DESIGN: Retrospective observational study. METHODS: Data were obtained for games (n = 791) contested by Western Australian and Victorian teams; including game location, start time, and outcome. Start times were categorised as afternoon, twilight, or night. Game-day maximum temperature (°C) for afternoon games was obtained from the Australian Bureau of Meteorology. Mixed effects generalised linear models examined evidence for a circadian advantage to Victorian teams in afternoon games, and to Western Australian teams in night games. Models examined evidence for an advantage to Western Australian teams as game-day temperature increases. RESULTS: Odds of winning and point margin for home games played in the afternoon, twilight, and night, were not different between Victorian and Western Australian teams (p > 0.05). For afternoon games, each 1 °C increase in temperature improved odds of Western Australian teams winning by 11% (p < 0.001) and their point margin by 2.1 points (p < 0.001). For games played in Victoria, each 1 °C increase in temperature improved odds of Western Australian teams winning by 6% (p = 0.028) and their point margin by 1.7 points (p = 0.005). CONCLUSIONS: There is no evidence here that circadian misalignment between teams influences game outcomes in the AFL. Western Australian teams are more likely to win afternoon games played in warm conditions. This may reflect superior heat acclimatisation among AFL players based in Western Australia.