At the 2014 World Cup, players sprinted 5% less in the hottest matches. Fourteen of 16 host cities in 2026 are forecast past that heat line, and pressing teams stand to lose the most.

Sprints fell about 5% in the 2014 heat

George Nassis and colleagues studied all 64 matches from the 2014 World Cup in Brazil and found that high environmental heat cut sprints by roughly 5% and pulled down high-intensity running. ¹ Players ran less at top speed, ran more at low intensity, and completed more passes to compensate.

A companion study from the International Journal of Biometeorology measured the same tournament and found the drop-off threshold sat at about 28°C and 60% relative humidity. ² Below that, the weather barely moved the running numbers. Above it, the high-speed actions went first.

Sprints, repeated accelerations, and recovery runs dropped before passing did. Matches in the heat ended up slower, with more of the ball moving at walking pace and fewer sprints to break a defensive line.

Pressing teams lose more than possession teams in the heat

A side that wins through pressing and transition needs counterpresses after turnovers, sprints to close passing lanes, and recovery runs when the press breaks. The 2014 data shows counterpresses, lane-closing sprints, and recovery runs all fading first. A side that already keeps the ball and makes the opponent chase loses less, because its game was never built on the sprint count.

Hot afternoons narrow the gap between a high-output pressing team and a low-output possession team, and in a single knockout match that difference can decide who advances. The pressing team loses more of the actions its game depends on.

Long flights and short rest compound the running loss. A separate study of weather, travel distance, and rest across the 2014 tournament found that a hot match after a long trip and three days’ recovery costs more than the heat alone would suggest. ⁸ The 2026 schedule across the United States, Canada, and Mexico builds in exactly those long flights, short turnarounds, and hot afternoon kickoffs.

Altitude moves results half a goal per 1,000 metres

Heat is statistically messy, because temperature, humidity, kickoff time, and travel all move together. Altitude separates more cleanly, and the effect is larger. Patrick McSharry, in a BMJ analysis of 1,460 South American international matches played over more than a century, found that each additional 1,000 metres of altitude difference between two teams shifted the expected goal difference by about half a goal. ³

For two teams from the same altitude, the home side won with probability 0.537. For Bolivia at home in La Paz against a sea-level opponent such as Brazil, an altitude gap of 3,695 metres, that rose to 0.825. When the fixture moved down to sea level, the high-altitude side still kept an advantage. Lowland teams, the study found, could not acclimatise quickly enough to erase the gap, and the disadvantage held whether they played high or low. ³

Altitude will matter less in 2026 than heat, since Mexico City and the other elevated venues are a minority of the schedule. But half a goal per 1,000 metres shows the mechanism directly. Teams adapted to the condition gain measurable goals, and teams that arrive without adapting give them up. Heat works the same way, though temperature, humidity, travel, and kickoff time all overlap and make the effect harder to isolate.

Most 2026 venues are projected past the unsafe line

The 2026 tournament is the most heat-exposed World Cup yet planned. A 2025 study projects that 14 of the 16 host cities are likely to exceed the 28°C wet-bulb globe temperature mark under typical summer conditions. Miami and Kansas City matches in the late-afternoon slot carry more than a 30% chance of crossing that mark in an average summer, above 50% in a hot one, and the MetLife Stadium final at a 3pm kickoff sits at roughly 30% in a typical year and 55% in a hot one. ⁴

FIFPRO, the players’ union, treats 28°C WBGT as the unsafe line and 32°C WBGT as the extreme line where postponement should be on the table. FIFA has mandated three-minute cooling breaks at the 22nd and 67th minutes of every match regardless of conditions. FIFA has tried to push the worst games into cooler windows, but broadcast demand still drives afternoon kickoffs, and at least five matches are projected to start at the unsafe mark. ⁶

Cooling breaks also reset the match’s rhythm. A pressing side that has spent an hour chasing in 32°C gets a forced pause at the 67th minute. If its sprint count does not recover after the break, the possession side takes control of the final twenty minutes, holds the ball longer, and forces the tired pressing team to chase again from a deeper position.

Players already struggled at the 2025 Club World Cup

Last summer’s Club World Cup, played across the same North American venues, gave the clearest preview. Dortmund manager Niko Kovač said after a Cincinnati match that he was sweating like he had come out of a sauna. Chelsea midfielder Enzo Fernández called the conditions very dangerous and said everything becomes very slow — the same drop in intensity the 2014 sprint data measured. Juventus manager Igor Tudor said ten of his players asked to come off during a match against Real Madrid in Miami, where the temperature reached 30°C with 70% humidity. ⁵

The same day, Dortmund’s substitutes watched a first half from inside the locker room rather than the bench, sheltering from the midday Cincinnati heat. The MetLife final was played in roughly 85°F. Jürgen Klinsmann, who played for Germany at the 1994 World Cup, remembered Dallas at what he estimated as 120°F and said he was dying. ⁵ The country has hosted a hot World Cup before, and the football slowed then too.

Squads can train back part of the loss

Playing regularly in hot weather does not automatically prepare a squad. A climate-chamber study modelling the conditions projected for Qatar 2022 had 24 players perform repeated maximal efforts in neutral air and again in heat, and their repeated-effort capacity dropped in the hot condition. The authors recommended arriving early, running a recovery and acclimatisation camp so the body adapts to the climate, then rehearsing repeated high-intensity efforts in the heat before the first match. ⁷

A federation that brings its squad in two weeks early and trains in the local climate can recover part of the lost sprint output. A team that arrives late off a long domestic season, or rotates a thin squad through afternoon kickoffs, gives that preparation time away. The most exposed teams are the ones whose game depends on running and whose schedule leaves no room to acclimatise.

Sprint counts at hot venues start below the season baseline

In a hot afternoon match, both sides post fewer sprints than their season baselines, so any sprint comparison already starts below normal. A high pass-completion figure in those matches is not evidence of control. The 2014 data shows completion rises because the football has slowed and the ball is moving short and safe. A transition team will underperform an expected-goals model that ignores temperature, and the deeper, better-acclimatised squad picks up the difference.

The altitude numbers come from a century of South American internationals, the heat numbers from one tournament in Brazil plus laboratory work, and the 2026 figures are projections, not results. Altitude, heat, and lab findings should be treated separately, and a cold-weather knockout would reverse several of the effects described here. In every dataset, though, the side that could not adapt to the conditions gave up ground, whether the gap was metres of altitude or degrees of heat.

A 3pm Miami group game should show the slowdown within twenty minutes of the 67th-minute cooling break. If the pressing side’s sprint count drops while the possession side’s passing holds, the pressing team creates fewer turnovers, gives the opponent longer spells on the ball, and the match tilts from there.