for National Geographic News
Michael Phelps stands 6 feet 4 inches (193 centimeters) and weighs 195 pounds (88.5 kilograms), with the broad shoulders and slim waist common to the elite swimmer.
But consider his body measurements a little closer and it becomes clearer why Phelps is dominating these Olympic Games.
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He has an extended trunk and relatively short legs, a distinct advantage in the water. The inseam of his pants is reportedly 32 inches (81 centimeters), shorter than that of Hicham El Guerrouj, the great Moroccan runner, who is 5 feet 9 inches (175 centimeters) but all legs.
Phelps has double-jointed elbows, knees, and ankles, which allows him to bend himself like few swimmers can. His size-14 (European-size 48.5) feet are like giant fins.
Add to that the extraordinary work rate of his lungs and heart and Phelps appears almost superhumana different species from the rest of us.
Of course, he also trains extraordinarily hard. But so do others. To be an Olympic champion, a person's genes must first be preset for maximal athletic performance. After all, great athletes are born, then made better.
"The best athletes in the world are a result of good genes and optimal training," said Phillip B. Sparling, who is a professor of applied physiology at the Georgia Institute of Technology in Atlanta. "A person who has great dedication, motivation, and excellent training will not rise to the world-class level unless he or she has inherited a supercharged physiological system for the sport."
Stretching the boundaries of normal physiology, elite athletes strive primarily for strength, speed, and endurance.
The speed of a sprinter is determined in large part by physiology. Muscle proteins, including key energy-producing enzymes, are dictated by genes, as is muscle-fiber composition. Great sprinters, like Maurice Greene and Marion Jones, have a high percentage of fast-twitch muscle fibersfibers that contract quickly but tire quickly too.
A cyclist, in contrast, needs great lung capacity, for superior endurance, and strives for a high "VO2 max," the maximum amount of oxygen the lungs can consume. Lance Armstrong, not surprisingly, has an amazingly high VO2 max.
"Lance Armstrong is not only a supreme trainer and competitor, but he also possesses a Ferrari body," Sparling said. "His aerobic performancean essential key to endurance performanceis one of the highest ever measured in a cyclist."
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