The six-time Olympic gold medalist Usain Bolt, who set a hundred-metre world record of 9.58 seconds, in 2009. Photograph by Sandra Mailer / REX / AP

Three minutes, forty-three seconds, and thirteen hundredths of a second is the fastest that a human has ever run a mile, as far as we know. Hicham El Guerrouj, a Moroccan middle-distance runner who was then twenty-four years old, accomplished the feat in 1999, averaging slightly more than sixteen miles per hour as he sped around Rome’s Olympic Stadium track. A determined wisp of a man, El Guerrouj weighed a hundred and twenty-eight pounds at the time and stood five feet nine inches tall in his running socks. Those few who’ve come close to running a mile as fast as El Guerrouj have been roughly the same size, and that’s not a coincidence: if you wish to run middle or long distances quickly, it helps to travel light.

The Jamaican sprinter Usain Bolt, on the other hand, has “one of mankind’s most sculpted bodies,” as GQ put it a few years ago: he is eight inches taller than El Guerrouj and weighs more than two hundred pounds. When the six-time Olympic gold medalist set his hundred-metre world record of 9.58 seconds in Berlin, in 2009, at the age of twenty-two, he averaged more than twenty-three miles per hour, peaking at more than twenty-seven. He couldn’t sustain that pace over a continuous mile, of course; his best two-hundred-metre (19.19), four-hundred-metre (45.28), and eight-hundred-metre (2:10) times make that clear. So how much would Bolt slow down while running a full mile? Could he run that distance in less than, say, five minutes?

This hypothetical has been debated by running geeks for years. On the popular Web site

Johnson has a twin brother, though, named Weldon, a former Olympic-trials distance runner who co-founded the Web site with him. Weldon respectfully disagrees with his brother. “With training, I would think Bolt could break five minutes,” he told me. Other educated observers are willing to go even further. Zebulon Lang, an assistant track and cross-country coach at Cornell University, said, “I’m happy to go on record that I believe Bolt could run a mile in 4:20 right now.” Lang cites the strong fifteen-hundred-metre time (4:14) by the world-record-holding decathlete Ashton Eaton, as well as the impressive eight-hundred-metre début time (1:53) by Jeremy Wariner, a three-time gold medalist in the four hundred metres. Lang’s thinking, essentially, is this: if one of the best quarter-milers ever can become an élite half-miler, and perhaps the best decathlete ever can run what equates to a 4:34 mile, then the best sprinter of all time can at least run a mile as well as a strong high-school athlete.

But what about Bolt’s likely inability to pace himself over longer distances—not to mention his body’s spiking blood-lactate levels and relatively poor capillary density as his body exceeds its trained limits? (Running a mile quickly requires efficient consumption of oxygen and recycling of the body’s accumulating lactate; running a hundred metres quickly does not.) His mostly anaerobic training would hurt him in a mostly aerobic race, right? Probably. “Speed over short distances does not automatically guarantee relative speed over long distances,” Ross Tucker, a professor of exercise physiology at the University of the Free State, in South Africa, told me. “Mainly because the system used to produce energy sent to muscles is quite different. What a one-hundred- or two-hundred-metre sprinter relies on is incapable of meeting his demands over a mile. By definition, the training a short-distance sprinter does is in polar opposition to that of a middle-distance runner. One-hundred-metre speed translates pretty well up to four hundred metres. But after that there is a large change.”

Tucker, too, brought up Ashton Eaton. “If he runs 4:15 to 4:17” in the fifteen hundred metres “at the end of two days of decathlon competition, I reckon a fresh effort puts him at around 4:20 for a mile,” he said. “Yes, a decathlete’s training is necessarily geared towards more endurance than a one-hundred-metre runner, but I don’t think to the extent that they’re an irrelevant comparison. If Eaton is capable of a 4:20 mile with his training, then Bolt,” with middle-distance training, “won’t be much faster than 4:30, in my opinion.” If Tucker had to guess, he’d put his money on 4:45 to 4:50. “But the incentive for him would have to be large.”

There are relevant precedents one can cite, and they don’t bolster the case for Bolt’s success. The late American sprinter Florence Griffith Joyner, who won three Olympic gold medals and still holds world records in both the hundred (10.49) and two hundred metres (21.34), attempted to become a distance runner after her sprinting career ended. It didn’t work out well. Perhaps the most visually convincing argument against Bolt’s potential prowess in the mile is the footage of the nine-time Olympic gold medalist and sprinting specialist Carl Lewis struggling to run a 2:16 half-mile in his prime, in 1986, on television. It’s clear from his last lap that the man who was then the “fastest human in the world,” as the TV announcer calls Lewis, is spent. He makes the half-mile look hard. "There's no way Lewis would have finished that mile in under five minutes," Robert Johnson told me.

Bolt’s agent, Ricky Simms, won’t say whether he believes that his client could run a mile in less than five minutes. But Simms confirmed, over e-mail, that the world’s greatest sprinter has, in fact, never tried running that far: “Usain has never run a mile.”