Craig Pickering

The heat is on: preparing for the temperatures at the 2026 FIFA World Cup

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Every four years, the men’s FIFA World Cup takes over the world of sport. Football (I can’t quite bring myself to call it soccer) is probably the closest thing we have to a genuinely universal sport, with cheap equipment, simple rules, the ability to play almost anywhere. It is culturally embedded across Europe, Africa, and South America, with growing popularity in the Middle East, Asia, Oceania, and North America. Football truly is a global sport, with an estimated 270 million people involved in organised versions of the game, and many more playing in parks and streets across the globe. 

These strong roots of football as a game for all lead to the pointy end; elite football performance. This is primarily centred within the professional leagues in Europe, but has spread into the highest leagues in almost all countries. Since the 1990s, football has embraced sports science and research and innovation as a competitive edge. It hasn’t always been this way – when Arsene Wenger was appointed Arsenal manager in 1996, he brought fancy ideas such as banning chocolate, which almost led to a player revolt. Since then, sports science in professional football has grown significantly. The club that I support, Manchester United, has key roles such as Head of Sports Medicine, Head Physiotherapist, First Team Doctor, four First Team Physiotherapists, three First Team soft tissue therapists, a Head of Physical Performance, a Lead Physical Performance Coach, a Strength and Power coach, two reconditioning coaches, a Head of Sports Nutrition, a First Team Nutritionist, and six first team Performance Analysts. There is significant resource placed on the use of science as a performance edge, with a view on innovation too (there is even an academic journal, Science and Medicine in Football) dedicated to the topic. 

The influence of science in football cannot be overstated. In 1995, just before the scientific evolution of football, the game (in the UK at least) was very old-school; there was poor nutrition, drinking culture, generic fitness work, no focus on recovery, and very generic planning. Now, the player’s body is well managed as a key performance asset, which has led to matches themselves becoming faster and more intense. Enhanced analysis has driven tactical innovations, and a matching of physical requirements to the manager’s preferred tactical style. This has also led to recruitment, with teams seeking to sign players that best suit their style, looking to find the next diamond whilst minimising their risk. 

So, with the World Cup around the corner, I thought it was a good idea to explore some of the key sports science aspects surrounding it, before exploring how we can apply the same knowledge within track and field and other sports.

Heat acclimation strategies

In this first article, I’m going to look at performance in the heat; what it means for the World Cup, and lessons we can utilise ourselves as coaches. Performance in the heat is a crucial consideration for the 2026 World Cup because a number of venues (Atlanta, Dallas, Houston, Kansas City, Miami, and Monterrey) have been identified by FIFPRO as posing “an extremely high risk” of heat stress injury. This has been mirrored in academic research, with a 2024 study suggesting that 10 out of the 16 venues posed a significant risk. We have a rough idea of the impact this heat will have from a paper published earlier this year; here, the authors examined matches at the 2025 Club World Cup (held in the US), and how they were affected by the heat. The researchers found that higher temperatures in matches led to lower distances covered per game by the players, with higher levels of relative humidity leading to a lower number of high intensity sprints. This highlights that extreme climatic conditions can negatively affect physical performance, which in turn can affect gameplay. In addition, as core temperature increases, cognitive performance declines, negatively affecting the decision making of players and coaching staff. The challenge for teams is, therefore, to mitigate the effects of heat and humidity on their players to a greater extent than the opposition can, enhancing their performance in the match, and hopefully being more likely to win.

The most effective strategy to prepare athletes to perform in the heat is to undertake an active heat acclimation protocol beforehand. There are many different published methods for this (for example: this paper and this one). Generally, this process requires athletes to train in the heat, which then drives a number of adaptations that better prepare them for subsequent performance in hot conditions. Most active heat acclimation strategies call for 10-15 days of exercise-based heat exposures, where the core temperature exceeds 38.5°C and profuse sweating occurs. A challenge for this World Cup is that the first game takes place around 20 days after the completion of most European football seasons (where typically more than 70% of World Cup players are based), and just 12 days after the Champions League final. As such, players are going to struggle to get the required time to become fully heat acclimated prior to their first match.

Research has demonstrated that, given these constraints, a short-term heat acclimation block could mitigate some of the impact of performance in the heat, but not to the same extent as the longer block. For example, a 5-day heat camp with elite rugby players gave some positive adaptations, and such an approach might prove useful given the current constraints. A second potential approach is that of passive heat acclimation. These techniques typically utilise a sauna, heat chamber, or hot water immersion to elicit the required adaptations. Often, athletes train first, and then move into the passive heat component afterwards; research suggests that without pre-exercise, the size of acclimation is lower (but it does still occur). Given the time constraints, players could utilise passive heat acclimation techniques whilst still with their home club.

Mitigating heat on game day

Aside from pre-match preparations, teams will also focus on what they can do around the game to mitigate the effect of heat and humidity on performance. These methods include pre-cooling, where core temperature is lowered pre-match, which in turn increases the time for players to reach a core temperature where performance and/or health is negatively affected. Cold Water Immersion (i.e., ice baths) are the most effective technique here, but they often provide logistical challenges in a busy football stadium. Other potential techniques include the use of ice vests during warm-up, which have been shown to limit core temperature increases during the warm up with no negative effects on neuromuscular performance. The ingestion of an ice slushy has also been shown as effective in reducing core temperature.

It is not all golden, however. When using pre-cooling techniques, we must be careful to not go too far; reductions may negatively affect early match high speed running, and reduce the onset of sweating, making it harder for the body to cool itself. Similar approaches can be utilised at half-time, and ice slushies can be ingested during drink/cooling breaks during the game itself. 

It is also important to keep in mind that exercise in the heat increases the use of carbohydrates, as well as fluid and electrolyte loss. The latter two aspects can lead to dehydration, which has significant implications for both performance and health. As such, strategies to ensure athletes are consuming sufficient fluid, electrolytes, and carbohydrate are important. 

Key takeaways

Based on all the evidence to date, a recent review made the following strategy recommendations to mitigate the effects of heat for teams involved in the 2026 World Cup:

  • Acclimate – base camps in hot locations provide an opportunity to become heat acclimated, with at least five days required to deliver some adaptations. If coaches want to minimise time spent training in the heat (because session quality will suffer), then utilising passive heat acclimation methods may suffice. 
  • Recovery – becoming heat acclimated is physiologically taxing. As such, recovery should be closely monitored, and energy, fluid, and electrolyte intake matched to the demands. 
  • Cooling – cooling strategies before and during matches will reduce heat strain. This can include cold water immersion (the gold standard), but when not practical, methods such as ice slushies and cold towels / ice vests will assist. 

Impact of heat on track and field

For track and field coaches, the influence of heat and humidity on performance is quite well known – in part because the majority of major championships are in hot locations. At the 2019 World Athletics Championships, which were held in Doha, the marathon and walks events were held overnight so as to minimise the risks to athletes. At the 2021 Olympic Games, these events were also moved outside of Tokyo to a cooler location. Whilst the Tokyo Games were the hottest on record, Paris 2024 also provided a heat and humidity challenge, with a leading review making similar recommendations as for preparations for the 2026 World Cup. These recommendations included heat acclimation (passive or active, or both), the use of pre- and mid-cooling techniques, and the need to increase fluid, electrolyte, and carbohydrate intakes. 

From a performance standpoint, a 2010 paper gives us an eye-opening introduction to the effects of weather on performance, in this case in the marathon event. Here, the author analysed results from the Stockholm Marathon from 1979 to 2008, and then determined the effect of air temperature, humidity, wind speed, rain, and solar radiation on performance. Following analysis, the results showed that air temperature had the strongest effect on finishing time, and number of athletes not finishing the race. Warming from 10°C to 25°C cost an elite male around 5 minutes in performance—but perhaps more interestingly, it cost a 4-hour male runner around 23 minutes. This demonstrates that the effect of heat on performance is much greater for slower, and, presumably, less well-trained athletes. 

Coaches and support staff have long been aware of the negative effects of heat, and have taken steps to mitigate its influence, especially in endurance events. Today, many athletes in these events will utilise either passive or active heat acclimation methods, along with pre- and peri-event cooling with vests and ice slushies. Two reviews provide really good guidelines for how athletes might utilise active and passive heat acclimation strategies to support their performance. There is emerging evidence that exercise in the heat has a greater fatiguing effect on the central, but not peripheral nervous system – meaning that it may be more fatiguing for sprinters. This has implications for how sprinters prepare for multiple rounds and warm-ups during competitions. In practice, this means that the standard warm up protocol used in cooler, more temperate environments, may accelerate central fatigue in hot environments; as a result, it’s worth considering shortening or modifying warm-ups to reduce overall thermal load. It also suggests that recovery between rounds is more time-sensitive in the heat – prioritising cooling interventions (such as ice vests, cold towels, and ice slushies) during the recovery window between heats and finals may be more beneficial for sprinters than previously though. 

Final thoughts

While much of this article focuses on the negative impacts of heat and how to prepare or deal with them, there are some potential benefits too. Passive heat exposure appears to affect muscle contractility, which means that heat could become a potential training aid in driving key adaptations. As an example, an injured athlete could choose to train in the heat, because they can work at a lower intensity for the same adaptations. This is particularily relevant during rehab phases – a sprinter managing a soft tissue injury, for instance, could use post-session sauna or hot water immersion to maintain some adaptations whilst training load is reduced. The key constraint is that the physiological stress of passive heat exposure needs to be factored in to the overall load that is being monitored—it is not a free adaptation. Sessions should be progressive, beginning at around 15-20 minutes at 40°C, with core temperature and perceived exertion monitored. Athletes with cardiovascular conditions or who are already in a high-load phase should be excluded from this approach. 

That provides a bit of an idea for where to go next in the heat research. But for now, heat is clearly going to have negative effects on the performance of elite athletes, at both the World Cup and other major championships. The challenges for coaches and support staff to is adequately prepare athletes to deal with these demands.