Lance Armstrong is built differently from other people, and that is why he was able to be such a great athlete. Here are the details:
His oversized heart can beat over 200 times a minute and thus pump an extraordinarily large volume of blood and oxygen to his legs. His VO2 max—the maximum amount of oxygen his lungs can take in, an important measurement for an endurance athlete—is extremely high.
But other elite athletes have similarly powerful hearts and lungs. Instead, Coyle says, smarter training may have contributed to giving Armstrong an edge over his competitors.
"[He] is on top of the cycling world because of the combination and interaction of his genetic endowment, years of incredible training, competitive experience, and obsessive drive to achieve and persevere," said Phillip B. Sparling, a professor of applied physiology at the Georgia Institute of Technology in Atlanta.
Source: Lovgren, S. (2005 July 22). The science of Lance Armstrong: Born, and built, to win. National Gegraphic.