Mexico City's high altitude, situated approximately 2,240 meters (7,350 feet) above sea level, presents a significant physiological hurdle for athletes unaccustomed to such conditions. The thinner air, a result of lower atmospheric pressure, means each breath delivers fewer oxygen molecules to the body, forcing the heart and lungs to work harder to maintain performance.
An attempt to quantify this effect involved running a 5-kilometer distance in Mexico City less than 24 hours after arriving. The runner, who typically completes this distance in about 22 minutes, finished the Mexico City run in 24 minutes and 44 seconds. Within the first kilometer, a notable tightness in the chest was experienced, and breathing felt significantly more labored than usual. Legs also felt heavy, a sensation attributed partly to the altitude and partly to recent travel.
By the third kilometer, some adaptation occurred, with breathing settling and chest tightness easing, though the run never felt effortless. The fourth kilometer brought increased sweating and the onset of chafing, a condition that can be exacerbated by the salt buildup from perspiration. This phenomenon led to the recommendation of using Vaseline in similar conditions, a practice noted among military personnel undertaking altitude training.
The experiment highlighted that while the immediate effects are noticeable, such as increased breathlessness and a feeling of exertion, they are not insurmountable for elite athletes over shorter durations. However, the cumulative impact over a full 90-minute match is a significant concern. For professional teams, the challenge lies not in whether players can run, but in how every sprint, recovery, and change of direction demands incrementally more from their bodies.
Sports science preparation for such environments includes measures like training with hypoxic breathing devices designed to simulate some of the respiratory demands of altitude. While these devices cannot fully replicate the adaptations from living and training at altitude, they aim to expose players to some of the breathing challenges they might encounter. The focus is on mitigating, rather than eliminating, the effects of altitude.
This challenge is distinct from managing heat, as the availability of oxygen cannot be altered. The experience of a 5K run, while not a direct comparison to an international match, offered a glimpse into why altitude is a critical factor in tactical and physical preparation. In high-stakes matches, particularly in the closing stages when fatigue sets in, these small physiological margins could become decisive factors, especially for teams not acclimatized to playing at such elevations.