The factor of extreme altitude above sea level has imposed itself as one of the most complex environmental and physical challenges facing teams participating in the 2026 World Cup finals in Mexico, with a number of technical and medical staffs of teams that played their matches in the capital Mexico City expressing serious concerns about the effects of playing on the pitch of the historic Azteca stadium, which sits approximately 2,200 metres above sea level.
These altitudes cause atmospheric pressure and available oxygen in the air to drop by approximately 25% compared to coastal stadiums, leading to accelerated muscular fatigue, elevated heart rates, and a reduced ability for players to recover quickly during high-intensity running — something medical teams have described as the "oxygen trap", which grants host sides an enormous natural competitive advantage, turning the stadium into an impregnable environmental fortress.
In the face of these exceptional conditions, visiting teams' medical staffs have been compelled to adopt rigorous scientific strategies to mitigate the acute physiological effects of thin air. These include using altitude simulation technology in their prior training camps, relying on nutritional supplements and water bottles fortified with salts to boost oxygen flow in the blood, as well as choosing between two medical approaches: either arriving early — two weeks in advance — to acclimatise and produce additional red blood cells, or following a "fly-in, fly-out" mechanism by arriving immediately before the match to avoid the acute symptoms of altitude stress.
For its part, FIFA acknowledged the difficulties posed by the local geography, but affirmed that the match schedule had been designed in a way that takes into account the time intervals available for recovery. It noted that modern sports medicine possesses sufficient tools to handle these conditions, which are considered part of the historical character of the World Cup in Mexico, and regarded the new regulations permitting five substitutions per match as giving coaches additional flexibility to protect player welfare and ensure the tournament maintains its high technical tempo.