A new investigation analyzed over 997 thousand amateur football matches played in Germany and revealed an unexpected pattern: intense heat is associated with a reduction in the number of cards issued during the games.
A new investigation analyzed over 997 thousand amateur football matches played in Germany and revealed an unexpected pattern: intense heat is associated with a reduction in the number of cards issued during the games.
Researchers from Humboldt University of Berlin and the European University Institute in Italy conducted this study. They compared matches that took place in the same location, within the same league, and in the same season, covering the period from July 2022 to September 2025. Data on card incidence were correlated with the temperature recorded on the day of each match.
Although the general public and part of previous scientific literature indicated that high temperatures would lead to greater aggression among players, the research demonstrates that this trend reverses in extreme heat. Specifically, on the hottest days, there was a drop of approximately 15% in the total number of cards compared to the average observed in the study. The maximum temperature recorded during the analysis was 32 °C.
The authors suggest that this decrease occurs due to reduced physical contact on the field. Many infractions result from fierce disputes, such as tackles, jumps, and vigorous challenges. However, under extreme heat, athletes tend to conserve energy, which leads to a decrease in these types of plays and, consequently, fewer fouls.
The study notes that moderate heat can indeed increase irritability. However, aggressive behavior, which depends on physical contact, tends to decrease at extreme temperatures. The researchers argue that previous studies linking heat to aggression may have been influenced by being conducted in laboratory settings or using data from professional football, where conditions such as hydration breaks and climate-controlled environments are present, which are absent in the context of amateur football.
Additionally, the authors warn that the conclusions should not be generalized, given that the sample was restricted to amateur, predominantly male football matches, and the maximum temperature of 32 °C is lower than the peaks observed in heatwaves in other regions. The reduction in cards does not imply less physiological impact, but rather an energy conservation strategy by the players.