Statisticians have used a lower limit for 100-meter times of about 9.45 seconds, according to Tabata and other researchers. The exponential curve seen above -- which is drawn from an equation calculated to fit the world record data -- had been quite successful at predicting the steady progress of faster and faster 100-meter times. 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.

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.

But it could just be that mathematicians have been modeling the pace of progress wrong all along.