World Cup on Red Alert: The Environmental Challenges to Player Health and Performance

For the first time, the FIFA World Cup will be held across three countries—the United States, Mexico, and Canada—spanning a vast geographical area with host cities separated by thousands of kilometers.

This dispersion exposes athletes to a unique combination of environmental factors that could influence their health and competitive performance. Key challenges include extreme heat, altitude, air pollution, and the demands of travel. No previous World Cup has simultaneously presented these four risk factors.

While some of these environmental challenges have appeared in past World Cups—such as the heat in Brazil in 2014 or the altitude in South Africa in 2010 and Mexico in 1970 and 1986—no single tournament has ever featured such a complex combination.

Portugal's matches against the Democratic Republic of Congo and Uzbekistan, scheduled for 1:00 PM in Houston, could take place under intense heat. The analysis uses the Wet Bulb Globe Temperature (WBGT) index, a measure combining temperature, humidity, solar radiation, and wind to assess thermal risk during physical activity. The situation could be even more concerning for the match between Colombia and Portugal, the final group stage game set for 7:30 PM in Miami, where a WBGT of 30°C is expected.

International recommendations for exercising in hot environments vary. The American College of Sports Medicine (ACSM) suggests limiting or canceling intense physical activity when WBGT values exceed 30°C, while FIFA mandates hydration and cooling breaks during games when the WBGT surpasses 32°C.

On the other hand, the International Federation of Professional Footballers (FIFPRO) adopts a more conservative stance, recommending breaks starting at a WBGT of 26°C and the postponement or suspension of matches when values exceed 28°C.

The projections for the 2026 World Cup are particularly worrying. Of the 16 host venues, 14 typically experience WBGT values above 28°C during June and July, with six cities potentially reaching maximums between 30°C and 35°C.

Based on historical records: approximately 56% of stadiums could exceed FIFPRO's recommended limits for postponing or suspending matches; 25% could surpass FIFA's threshold for mandatory hydration and cooling breaks; and about 30% could breach the safety limits set by the ACSM.

These projections could be worsened by the increased frequency, intensity, and duration of heatwaves associated with climate change. Although some stadiums have retractable roofs and climate control systems capable of reducing thermal stress, extreme heat will remain one of the biggest challenges for athletes and teams during the tournament.

Given this scenario, competitive advantage may not solely depend on a team's technical or tactical quality. The ability to manage body temperature, accelerate recovery, and adapt players to climatic conditions could become a decisive factor throughout the tournament.

Elevated body temperature has significant implications for players' health and performance, such as: Health: Core temperatures above 39°C increase the risk of heat-related illnesses, including heat exhaustion. Physical Performance: The ability to perform repeated sprints and high-intensity actions, which are often decisive in football, decreases as body temperature rises. Cognitive Performance: Complex cognitive functions like decision-making, attention, and tracking multiple stimuli deteriorate when core and skin temperatures increase. Technical and Tactical Performance: Players tend to adapt their on-field behavior, reducing game intensity to preserve overall performance.

In extreme heat, teams also tend to have a higher percentage of ball possession and greater passing efficiency, adopting a more controlled style of play rather than one based on constant pressure. Additionally, cooling strategies before and during matches can limit the rise in body temperature, helping to protect players' health and maintain performance.

Cooling strategies are a key tool for reducing the impact of heat on players' health and performance. Cooling can be achieved through external methods, like applying cold to the body's surface, or internal methods, such as ingesting cold beverages. These strategies should be implemented before and during games.

The main goal of pre-game cooling is to create a thermal reserve before exercise begins, lowering body temperature and increasing the time it takes for players to reach temperatures associated with health and performance risks. Cold water immersion is considered the most effective strategy for removing heat from the body. However, its application in a competitive context presents significant logistical challenges, requiring specific infrastructure like temperature-controlled tubs and a ready supply of ice.

As a more practical alternative, ice vests have shown promising results. One well-known brand has created a technology where the inside of these vests contains a special gel that is frozen before use and then worn over jerseys. The gel thaws and cools the torso, helping to lower body temperature.

Another effective approach is to combine internal and external strategies, such as ingesting crushed ice while applying ice packs to the major muscle groups of the lower limbs. Despite the benefits, it is necessary to avoid excessive cooling.

An excessive reduction in muscle temperature can compromise the ability to perform explosive actions at the start of a match. Similarly, overly aggressive internal cooling can delay the onset of sweating, reducing the body's natural ability to dissipate heat.

On another note, Portugal has so far been fortunate to avoid altitude. Competing at 1,500 to 2,500 meters (as is the case in Guadalajara and Mexico City) requires a preparation period of about two to four weeks to promote important physiological adaptations, such as increasing total hemoglobin mass and maximum oxygen consumption.

These hematological adaptations improve aerobic capacity, making this an effective approach for acclimatizing before competitions at altitude. However, its practical application is often limited by the time constraints of the competitive calendar. The Portuguese national team is far more accustomed to heat than to altitude. Perhaps the only high-altitude training they'll do is lifting the championship trophy on the highest step of the podium.