Sweden’s men’s national team has been preparing for the test it will face Tuesday since well before The Blue and Yellow arrived in the U.S.—not only a showdown with current World Cup favorite France, but also a match played in temperatures that could surpass 90 degrees (32.2 degrees Celsius) by kickoff. 

Outside Stockholm, players trained in a climate-controlled room and were sent to the sauna afterward, preparing their bodies for hot and humid conditions, according to Scientific American. Some reportedly did cardio sessions in spaces set to 100 degrees. The country picked a base camp in Frisco, Texas, targeting a climate that over time can trigger physiological changes, including expanded sweat glands and improved blood circulation.

On Tuesday the team—which includes nine specialists across medicine, performance and psychology—could have an array of ice bags, cold towels, freezing vests and even cooling overshoes at their disposal. 

Much has been made of this World Cup’s mandatory commercial—sorry, hydration—breaks, which have paused action, even during indoor or rain-soaked matches. This week, fans might be too hot to boo the interruptions.

Temperatures are expected to exceed 90 degrees in New Jersey, Toronto, Miami, Kansas City and Philadelphia ahead of open-air matches in each location. Whichever teams keep the coolest, relying on a rapidly expanding set of scientific findings and new-age tech, could find themselves surviving the matches.

“This World Cup is the World Cup for the sports scientists, because the heat and hydration is such a huge factor,” UConn kinesiology professor and Korey Stringer Institute CEO Douglas Casa said. 

Many players got a taste of the U.S.’s summer heat—and the need to prepare for it—last year, during the Club World Cup. “It’s terribly hot,” Atlético Madrid and Spanish midfielder Marcos Llorente said after playing in 90-degree conditions last June. “My toes were sore, my nails were hurting. I couldn’t stop or start.”

Brazil has spent more than a decade working with Gatorade, which now leverages a wearable patch made by Epicore to track how individual athletes lose fluid and nutrients over the course of training and matches. Hydration formulas are then tailored for each player, alongside recommendations for how much they should drink. (Brazil won its round of 32 match over Japan Monday, indoors in Houston.)

Wearable—and ingestible—sensors have given scientists new ways to track athletes and test potential interventions. “The two holy grail items in the heat/hydration space have been realtime assessment of body temperature and realtime assessment of hydration status,” Casa said. “In the last five years, I think there’s been more progress in hydration monitoring and body temperature monitoring from a wearable perspective than there had been in the entirety of human history beforehand.”

Therabody released its first thermoregulation device in June, just in time to send England’s national team 18 CryoTherm Palm kits. Three Lions players and staff members previously consulted on the product’s development.

“[England was] one of the most forward-thinking teams that we had contacted and had a relationship with,” Therabody chief science officer Tim Roberts said. “They’d been planning cooling strategies and heat mitigation and acclimatization, they’ve been planning for really, honestly, two years, or more.”

Building on previous research showing that sticking one’s hand in cold water midway through exercise improved results, Therabody’s dumbbell-shaped tool, called CryoTherm Palms, promises to lower core body temperatures by cooling blood vessels in the hands. Though England didn’t break out the tools (retail: $400 each) during group stage matches, which were either held in A/C or in rain, Therabody said it has seen athletes benefit from palm cooling even in room temperature environments. 

England will play indoors in Atlanta on Wednesday, before potentially taking on Mexico in Mexico City. A sticky showdown with Brazil in Miami could await the winner of that match.

When it gets hot, CryoTherm Palms can also be combined with more traditional cooling practices. 

“The key to cooling is covering as much skin surface area as possible with cold water,” Casa said. “You want to have cold towels on your upper back … your legs, your arms, on your head, neck, cheeks.”

During a particularly steamy 0-0 draw in this summer’s group stage, Colombia players put on ice vests while Portugal’s stars opted more often for chilled neck collars to combat Miami’s conditions during hydration breaks. Adidas has equipped its partnered teams with kits including vests, lightweight jackets designed to be worn over the vests to keep the coolness in, and overshoes packed with gels to reduce foot temperature and swelling.

What Adidas calls its Climacool system can be used during training, when players have more time to regulate their body temperatures, as well as during the few minutes mid-match teams now have to recover.

“Given the limited time available during the break, the system has to deliver rapid, measurable cooling within very short windows,” Adidas director of athlete performance Margherita Raccuglia said. The company turned to a particular gel formula designed for an immediate cooling effect while ensuring the gear could be put on and taken off with a zip. Premier League giants Arsenal and Manchester United were involved in developing the system, Adidas said, which also draws from Formula 1 science.

And yet, footballers seem remiss to adopt one performance-boosting technique embraced by F1’s drivers: sitting down. 

FIFA’s hydration breaks each last three minutes. During that time, players must remain on the pitch rather than retreat to sideline dugouts. But otherwise, rules are relatively lax regarding the equipment teams can pull out, up to and including laptops. That gives wealthier teams one more potential advantage in international play, with the ability to bring scientists and gear smaller countries might not be able to match. 

Still, teams don’t seem to be optimizing the breaks, getting players to sit or lie down so they could be more completely covered in cooling gear, as they likely do inside the locker room at halftime. 

“Psychologically, the players wouldn’t want to sit,” Roberts said. “It’s purely the nature of the sport and the culture within the sport that they’re not going to sit down.” But then again, cultures evolve. Roberts added that teams are likely keeping things as familiar to players as possible with every-match hydration breaks still new. 

If the stoppages become permanent, seats wheeled onto the pitch could be next—a la college basketball timeouts. They could even be sponsored, if that helped.