All athletes, from weekend hobbyists to third-string high-school quarterbacks to Olympic stars, look for that special edge to perform better. But new research shows that one of the most important factors might be something you're born with: bellybuttons. Specifically, where your bellybutton--and thus center of gravity--is located on your torso may determine your inherent ability to run and swim. Agence France-Presse's Karin Zeitvogel reports on the results of a scientific study published in the implausibly named International Journal of Design and Nature and Ecodynamics:

What's important is not whether an athlete has an innie or an outie but where his or her navel is in relation to the rest of the body.
... The navel is the center of gravity of the body, and given two runners or swimmers of the same height, one black and one white, "what matters is not total height but the position of the belly-button, or center of gravity," Duke University professor Andre Bejan, the lead author of the study, told AFP.
A higher belly button makes you a better runner, says Bejan. "Locomotion is essentially a continual process of falling forward, and mass that falls from a higher altitude, falls faster." But a lower belly button makes you a better swimmer. "Swimming is the art of surfing the wave created by the swimmer. The swimmer who makes the bigger wave is the faster swimmer, and a longer torso makes a bigger wave."

The study also connects belly-button location, and thus one's ability at running versus swimming, to race.
Individuals of West African-origin have longer legs than European-origin athletes, which means their belly-buttons are three centimeters (1.18 inches) higher than whites', said Bejan. That means the black athletes have a "hidden height" that is three percent greater than whites', which gives them a significant speed advantage on the track.
It's probably not a complete explanation for what Zeitvogal calls "the reason why blacks dominate on the running track and whites in the swimming pool." After all, "black" and "West African" are not synonymous, and of course most people are neither West African nor European.  But it's an interesting idea.