For the first time in the history of the World Cup, FIFA is requiring all players to take mandatory water breaks to protect them from high temperatures — but the new rule has drawn criticism from various quarters.
FIFA said the mandatory breaks are intended to ensure a level playing field for all teams in all matches, and that the rules are based on experience from previous tournaments, including the Club World Cup held in the United States last summer, when temperatures rose significantly.
Some coaches said the breaks make sense in high temperatures, but questioned their value in every match. The stoppages have also drawn criticism for their impact on the viewing experience, as television broadcasts are cut away to show advertisements.
Javier Aguirre, the head coach of the Mexican national team, said they are making full use of the water breaks.
"We are not allowed to come down onto the pitch, but the players can approach us while drinking water and we can give them instructions," he said. "We use the opportunity to correct any mistakes during the match — it is good for coaches."
Yuri Hosokawa, from the Faculty of Sport Sciences at Waseda University in Japan, said that when the body's core temperature exceeds 40.5 degrees Celsius, athletes may experience confusion or aggression, or lose consciousness.
Hosokawa co-signed a letter addressed to FIFA urging stricter heat guidelines to ensure player safety, including that cooling breaks last at least 6 minutes.
Exertional heatstroke is among the leading causes of death among athletes.
Ryan Calsbeek, a professor of biological sciences at Dartmouth College, said that human body performance improves when it is warmer, but there is a critical threshold beyond which performance does not merely plateau — it drops sharply.
"The body begins to break down, losing the ability to cool itself quickly enough, and physiological mechanisms become impaired," he added.
This occurs when the wet-bulb globe temperature — which accounts for temperature, humidity, cloud cover, and wind — exceeds approximately 95 degrees Fahrenheit (35 degrees Celsius), although some individuals are more heat-tolerant than others.
In a 2024 study, researchers found that 3 minutes reduced athletes' core body temperature by 0.04 degrees Celsius during a simulated run in a heat chamber — but this occurred under ideal conditions, in which they drank between 350 and 400 millilitres of cold water and placed a cold towel over their shoulders.
Julien Périard, a co-author of the study and director of the Research Institute for Sport and Exercise at the University of Canberra, who also signed the letter, said that placing ice towels on a player's shoulders could be beneficial, but only on the condition that the player also drinks water.