High altitude can shrink an athlete's oxygen by fifteen percent
When the world's elite soccer teams meet in Mexico City, they battle an invisible opponent that saps their muscle power before the first whistle blows.
At 7,350 feet above sea level, the air in Mexico City is so thin that a professional athlete's aerobic capacity—the maximum amount of oxygen their body can use—drops by roughly fifteen percent. This environmental tax effectively turns a marathon runner into a casual jogger. Because there are fewer oxygen molecules per breath, the heart must beat faster and the lungs work harder just to maintain a baseline pace. Teams that fail to arrive weeks early to trigger the production of more red blood cells often find themselves gasping for air by the sixtieth minute.
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