LOS ANGELES — For the first time in World Cup history, FIFA is mandating all soccer players take hydration breaks to protect them from the threats of extreme heat. But the new rule has sparked criticism from two very different groups.
Some experts have warned that this summer's World Cup — co-hosted by the U.S., Mexico and Canada — could be the hottest in the tournament's history. In response to concerns about extreme heat, FIFA implemented three-minute hydration breaks midway through each half regardless of temperatures. But some critics say they're interrupting the game's flow and give coaches a chance to shift momentum in their team's favor, while some scientists have said the breaks are too short to make a significant impact on cooling and rehydration when conditions are sizzling.
"When we look at the three minute hydration breaks, we're really looking at this as a way to mitigate anything that could potentially lead to an incident or an emergency," said Joshua L. DeVincenzo, assistant director of applied research services at Columbia University's National Center for Disaster Preparedness.
Here's a look at the heat risks players face and what the hydration breaks can do:
FIFA's mandatory breaks, regardless of temperatures
This World Cup is the first to implement mandatory three-minute cooling breaks midway through each half, regardless of temperatures or whether stadiums are enclosed and/or air conditioned.
The governing body said it was to "ensure equal conditions for all teams, in all matches," and the rules draw upon the experiences of past tournaments, including the FIFA Club World Cup in the U.S. last summer where temperatures soared into the 90s F (mid-30s C) and above in many areas.
Some coaches said the breaks make sense when temperatures are extreme, but they questioned whether they were necessary at every match.
Even highly-trained, elite athletes can get heat stress
Athletes pushing themselves physically in hot and humid conditions risk getting what's called exertional heat illness. It happens when the body's temperature gets too hot and is accompanied by significant strain on the heart, nerves, muscles and central nervous systems.
Common symptoms include muscle cramps, extreme fatigue, impaired performance, headache, irritability, nausea, dizziness, cramping and dehydration.
When internal body temperature exceeds 105 F (40.5 C), athletes might feel confused, aggressive or lose consciousness, said Yuri Hosokawa, associate professor at the Faculty of Sport Sciences in Japan's Waseda University, in an email, "all of which are characteristic signs of exertional heat stroke and require immediate medical attention." She co-signed a letter to FIFA in May urging stricter heat guidelines for player safety, including that cooling breaks be at least six minutes.
Exertional heat stroke while playing a sport is among the leading causes of death in athletes.
Dehydration also exacerbates the risk. Athletes in the heat can sweat 1 to 2 liters (50 to 67 ounces) an hour, and most drink less liquids than they expel. Losing as little as 2% of one's body weight to dehydration can impair physical performance.
Ryan Calsbeek, professor of biological sciences at Dartmouth College, said the human body performs better when it's warmer, but there's a critical threshold above which that improvement in performance not only stops, but precipitously drops off.
"Your body starts to really fall apart, you lose the ability to cool off fast enough," he said. "And the physiological mechanisms just break down." That happens when the wet bulb globe temperature, which includes temperature, humidity, cloud cover and wind, reads above about 95 F (35 C), though some people will be more heat tolerant than others.
The increased confusion from extreme heat could impact an athlete's ability to make strategic decisions, he said.
"It's these marginal differences in performance that I think can determine the outcome of a match," Calsbeek said. "If you have individuals that do better in extreme conditions, whether it's extreme heat or high altitude or whatever the case may be, those small differences could play a critical, pivotal role in determining the outcome."
Hydration breaks should be longer, some experts say
The three-minute mandatory hydration breaks are meant to protect players, and referees, from extreme heat illness and help them maintain their physical performance.
In that time, players can cool off and replenish lost water and salt from sweating, but how effective it is depends on how aggressive the cooling methods are.
That could mean putting wet, cold towels on the exposed parts of a player's body, such as the neck, head, back and arms. If done well, that could reduce their body temperature by about 0.22 F (0.12 C) per minute, said Douglas Casa, CEO of the University of Connecticut's Korey Stringer Institute who also co-signed the letter to FIFA.
"Some people can tolerate a little more fluids comfortably and then do intense exercise. Some people can't because it sloshes around in their stomach and they don't feel super comfortable, so they might not drink as much in such a short period of time," he added.
The time, he said, dictates the volume of impact, whether from fluid or cooling, and "that's why we're suggesting doing something like five or six minutes, because it just makes such a big impact when you're dealing with a change of that magnitude."
But how much time a player needs to recover also varies. "Depending on your body, you might need more or less time. But those kinds of breaks are crucial so that your body isn't just being forced to keep trying to play catch up... to keep trying to cool you down without any kind of rest or a break," said Bharat Venkat, director of the Heat Lab at the University of California, Los Angeles.
As our planet gets hotter, mandating hydration breaks and changing where, when and how sports are played will be necessary.
"No matter what sport you play, there's going to be adjustments that have to be made in the face of climate change," he said.
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