Herculez Gomez had been playing professional soccer in Mexico for several years when he arrived with the United States national team for a vital World Cup qualifier at Azteca Stadium in 2013.
Experience had taught him that at Mexico City’s elevation of more than 7,300 feet, it was not just the home team, or the 100,000 fans, or the laser pointers and the projectiles that visitors had to overcome. There was also the matter of the thin, polluted air itself.
Still, what Gomez found in the locker room that day surprised him.
“We had oxygen tanks before the game and at halftime, and I remember thinking: ‘This is a little exaggerated, right?