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As astonishing as Usain Bolt's record-breaking 100-meter sprint was, his time of 9.69 seconds is nowhere near what biostatisticians predict is the natural limit for the human body.

But because he broke the mathematical model that had fit 100-meter record data for almost a century, Bolt's incredible performance could reset how fast researchers believe humans ultimately can run.

"This trend seems to defy simple curve fitting," wrote Tatsuo Tabata, director of the Institute for Data Evaluation and Analysis in Japan. Of course, a curve-fit just gives a viewable form to scattered data. It implies no hard limits, trends, or predictions. Bolt is fast and his post-race quote was: he didn't care about medals or records. He wanted to win against the other runners. That's why he eased up. That is true sportsmanship. Not racing some clock. Though if he hadn't slowed down near the end of the 100 meters, well, he would have been faster.

But Bolt's recent string of world records was clearly not an expected event: The model didn't predict a 9.69 until almost 2030.

The new world record is likely to rejigger the equations they use to calculate the maximum human speed.

Mathematicians like Noubary don't use the body's physiology to assess human physical limits. They were merely working with data that suggested that human speed increases were decelerating and would eventually stop completely. Indeed, in some events, like the long jump, the pace of record-setting has slowed nearly to a stop. That record has only been broken twice since 1968.

Peter Weyand, a physiologist at Southern Methodist University in Dallas who focuses on the biomechanics of running, said that mathematical models could never predict how fast humans might eventually run.

He suggested that it's impossible for mathematicians to predict the magnitude of the freakiness of athletic talent at the extreme margins of humanity. Bolt, it turns out, is a perfect example.

Weyand, who has conducted research on the body types of the top 45 100-meter sprinters in the last 15 years, said that almost all elite runners conform to the body norms for their race length, except for the most-recent Olympic champion.

"Bolt is an outlier. He's enormous," Weyand said. "Typically when you get someone that big, they can't start."

That's because muscle speed in animals is generally tied to their size. For example, rodents, being much smaller than elephants, can move their muscles much faster. The same holds true for human beings. Sprinters are short and have more fast-twitch muscle fibers, allowing them to accelerate quickly, but compromising their ability to run longer distances. Four hundred-meter runners, almost always taller, have the reverse composition of muscle fibers.

Bolt, though, combines the mechanical advantages of taller men's bodies with the fast-twitch fibers of smaller men.

"We don't really know what the best form is and maybe Bolt is redefining that and showing us we missed something," said biomechanicist John Hutchinson of the Royal Veterinary College at the University of London, who studies how animals move.


 
 

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