The heat strikes immediately. While you may think you’re prepared, the sensation is still a jolt to the system. Sweat begins to form almost instantly, and taking your first deep breath feels like inhaling air from a hair dryer.
This is the reality for some players participating in this summer’s World Cup in North America.
In a specialized lab located on the south coast of England, Precision Fuel and Hydration can replicate the conditions faced by teams at various tournament venues. To grasp what it’s like, I completed a 30-minute run followed by a 20-minute uphill walk—approximately half of a 90-plus minute football match—under simulated conditions reflecting those in cities like Miami or Monterrey, Mexico.
Even at a fraction of the intensity of professional players, there was an overall body weight drop of 0.64% after 50 minutes of exercise. My core body temperature rose by 1.55 degrees Celsius. From these figures, it’s estimated that physical performance capacity declined by about 10% in less than an hour.
Even after the workout, my face, hands, and feet felt uncomfortably warm. Thankfully, this simulation had a clear endpoint, unlike players at the World Cup, who face the challenge of maintaining peak performance with matches every few days. Once the final whistle blows, the focus shifts to rapid recovery for the next game.
What are the conditions like at the World Cup?
Playing conditions are assessed using the Wet Bulb Globe Temperature (WBGT) index, which measures heat stress by considering air temperature, humidity, wind speed, and solar radiation. When the WBGT reaches 28 degrees Celsius, organizations like FIFPRO recommend that games be postponed.
While it’s not an exact science, research from Precision Fuel and Hydration indicates that around 25% of matches during the World Cup could occur in conditions exceeding a WBGT of 26 degrees Celsius, with some predictions suggesting temperatures might surpass 28 degrees Celsius. Venues at greatest risk of exceeding these benchmarks include open-air stadiums in southern U.S. and northern Mexico, such as Monterrey, Miami, Kansas City, Missouri, Philadelphia, New York/New Jersey, and Boston.
In May, a group of experts from health, climate, and sports performance wrote an open letter to FIFA, warning that players would encounter “worrying levels of heat stress” during the tournament.
Dr. Lindsey Hunt, Senior Sports Scientist at Precision Fuel and Hydration, emphasized, “Heat doesn’t just make players uncomfortable; it alters the game’s physiology.”
As core and skin temperatures rise, the body diverts blood from working muscles to regulate heat, resulting in fewer high-intensity runs, fewer repeated sprints, and a slower overall pace, particularly late in each half.
What does heat do to performance?
In May, tennis player Jakub Mensik collapsed after playing for over four hours at the French Open in temperatures peaking at 95 degrees Fahrenheit, requiring a wheelchair to leave the court.
Afterward, Mensik remarked that his body simply “turned off.” He described the conditions as “insane” for play.
Conversely, when Scotland launched their World Cup campaign against Haiti in Boston on June 13, the temperature was a cooler 77 degrees Fahrenheit. However, even in a late evening match, the North American climate still took its toll.
Bournemouth winger Ben Gannon-Doak performed admirably in Scotland’s 1-0 victory but expressed relief when substituted after 75 minutes. “I needed to come off,” he admitted. “Both my calf muscles decided to leave the stadium before I did. I cramped up a bit and was more than happy to take a seat.”
Every athlete is unique, but extreme heat could diminish performance by as much as 20% to 30%.
“The initial signs of heat exhaustion may be misleading, as they often resemble regular fatigue,” Hunt explained. “A player might appear to be working harder for less output, struggling to follow opponents or making unusual mistakes as the game progresses.”
“However, the most concerning symptoms are cognitive—like confusion, lack of coordination, or a rapid decline in performance or cessation of sweating. At that stage, it transitions from a performance issue to a medical emergency.”
How can it be combatted?
The conditions in the U.S., Canada, and Mexico have influenced nearly every facet of the teams’ preparations for the tournament. Netherlands coach Ronald Koeman even suggested that England’s squad selection was significantly influenced by the weather.
“You can infer how they will play based on their squad choices,” Koeman noted. “They are likely to emphasis on corners and throw-ins, which require less energy in hot conditions.”
Conversely, England coach Thomas Tuchel asserted that their preparations have been rooted in science rather than altering the style of play. England has prioritized acclimatization during training sessions in West Palm Beach, Florida, with workouts conducted in temperatures soaring to 90 degrees Fahrenheit.
“We understand how each player individually reacts to heat, and we have implemented cooling strategies,” Tuchel said prior to the World Cup.
“We have benefited from collaboration with Team GB and specialists worldwide to devise solutions that aid player adaptation. We know precisely how long to expose them to heat during pre-camp training, ensuring we avoid over-exertion.”
England’s preparations began over a year ago, with the squad training in heated tents during a camp in Spain. Additionally, staff employed digital capsules to monitor each player’s core temperature and assess how they adapt to severe heat.
“While you can’t out-train the weather, you can ensure your team is adequately prepared,” Hunt advised. “Effective heat acclimatization, timely arrival, and adjusting to the local time zone won’t guarantee victory, but they can help maintain performance and recovery potential. In a tournament where every small edge counts, that’s an advantage worth securing.”
“Generally, the largest benefits come from mitigating disadvantages rather than enhancing capabilities: arriving acclimated, resting well in the appropriate time zone, and recovering effectively between matches.”
Could conditions decide the World Cup winner?
The answer is a resounding yes. Betting markets place France and Spain as the leading contenders for the World Cup title, based on their strong squads and recent tournament success. France has reached the last two World Cup finals, while Spain holds the title of reigning European champions.
However, in the 22 World Cup tournaments since the inaugural event in 1930, only two European teams have claimed victory outside their home continent—Spain in South Africa in 2010 and Germany in Brazil in 2014. The last World Cup held during a North American summer was in 1994, where Brazil emerged victorious.
Advancements in the science of handling extreme conditions suggest that teams will be better prepared than in previous tournaments. However, history indicates that the major European squads will need to contend with the elements if they hope to secure the World Cup trophy.