Reacción a "Most sites in North America that will host the 2026 World Cup are at high risk of extreme heat"

The study modelled the risk of severe heat stress and the potential for water loss to exacerbate this stress in professional footballers, as well as the impact of low oxygen levels at altitude in various stadiums across Canada, the US and Mexico, ahead of the upcoming 2026 FIFA World Cup. The authors found that ten of the 16 stadiums where the 2026 World Cup will be played presented a very high risk of extreme heat stress conditions.

The study is a positive step towards moving beyond the Wet Bulb Globe Temperature (WBGT) index and determining whether environmental heat stress increases the risk of exercise-induced heat illness in football players. By using the exercise-adjusted Universal Thermal Climate Index (UTCI), the authors took into account not only environmental conditions, but also the players’ activity level (the metabolic heat they produce), their speed of movement (the potential for heat loss through airflow), as well as their clothing (a potential barrier to heat loss). In contrast, the WBGT uses only environmental conditions (ambient temperature, humidity and solar heat load) to determine the severity of an environment, without taking into account the specific characteristics of the sport and the player.

Although the approach used in the study is a step forward, the results are likely to underestimate the risk of experiencing conditions of extreme heat stress. This is because the highest work rate that can be incorporated into the UTCI is 285 W/m², which, as the authors acknowledge, is approximately half, if not less, of the work rate endured by professional players during a competitive football match. For the estimation of water losses through sweat, a work rate of 450 W/m² was used, which is closer to, though still lower than, that which players would endure. Nevertheless, this approach predicted that sweat losses in excess of 1.5 kg/h would occur mainly in three stadiums (Arlington, Monterrey and Houston). However, sweat losses in excess of 1.5 kg/h are likely to occur at other venues where higher work rates are maintained, particularly if environmental conditions are more severe than anticipated in the model.

Ultimately, the study’s findings may help tournament organisers to optimise match scheduling, but FIFA needs to take action regarding its current policy of using a WBGT of 32 °C to implement cooling and hydration breaks during matches. We have recently demonstrated the effectiveness of FIFA’s hydration and cooling breaks in male players during a simulated match. We have also recommended the development of a football-specific heat stress policy with categories of measures (e.g., cooling break, cooling break with extended rest, postponement/cancellation) that take into account players’ evaporative heat loss requirements and the environment’s evaporative capacity, based on prevailing environmental conditions and players’ activity and attire. Such a policy could be implemented at the 2026 World Cup, as well as at the 2030 World Cup in Spain, Portugal and Morocco, to protect players’ health and the integrity of the game.