Specifically, while the average human has gained about 1.9 inches in height since 1900, Charles' research showed that the fastest swimmers have grown 4.5 inches and the swiftest runners have grown 6.4 inches.

The theoretical rules of animal locomotion generally state that larger animals should move faster than smaller animals. In his contructal theory, Bejan linked all three forms of animal locomotion -- running, swimming and flying.

Bejan argues that the three forms of locomotion involve two basic forces: lifting weight vertically and overcoming drag horizontally. Therefore, they can be described by the same mathematical formulas.

Using these insights, the researchers can predict running speeds during the Greek or Roman empires, for example. In those days, obviously, time was not kept.

'In antiquity, body weights were roughly 70 percent less than they are today,' Charles said. 'Using our theory, a 100-metre dash that is won in 13 seconds would have taken about 14 seconds back then.'

'In the future, the fastest athletes can be predicted to be heavier and taller,' Bejan said, according to a Duke release.

The results were published online in the Journal of Experimental Biology.