If that sounds crazy, it's time for a lesson on physiology. Everyone is born with two types of muscle fibers: type I, also known as slow-twitch; and type II, or fast-twitch. Fast-twitch muscle fibers are the ones you think of when you imagine a bodybuilder: they're large and powerful, but not very efficient. Slow-twitch muscle fibers are the opposite: while smaller and relatively weaker than fast-twitch fibers, they're efficient, with great endurance—think of the wiry frame of a typical marathon runner. While most people start out with equal numbers of each fiber type, specific training can convert one type to another. For example, sprinters like Bolt typically have 65–85 percent fast-twitch muscle fibers, while world-class distance runners have that same percentage of slow-twitch muscle fibers. And there's the rub: if you want to be a world-class sprinter, you need all the fast-twitch muscle fibers you can get. If Bolt were to train by running longer distances—even one mile—his body might begin to convert some fast-twitch fibers to slow-twitch, and his legendary sprinting speed would suffer. There are other reasons he might not run a mile, too. As Ross Tucker, a professor of exercise physiology, told the New Yorker, "The system used to produce energy sent to muscles is quite different [over short distances than over long distances]. What a one-hundred- or two-hundred-metre sprinter relies on is incapable of meeting his demands over a mile." To a layperson, sprinting 200 meters might look the same as running a mile, but the skills couldn't be more different. Robert Johnson, cofounder of LetsRun.com, may have said it best: "To expect Bolt to be good at the mile simply because he is the world's greatest sprinter would be like expecting a great three-hundred-and-twenty-pound N.F.L. offensive lineman to be good at playing running back simply because he's a great football player. It's ludicrous."
Now that you know this, you may think you could outrun Usain Bolt in the mile. Do you have a shot? Take a tour of your muscles, then see how quick Bolt really is, in the videos below.