Belly Button

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

"Locomotion is essentially a continual process of falling forward, and mass that falls from a higher altitude, falls faster," Bejan explained.
The navel is the center of gravity of the human body and since the West African-origin runners have longer legs and therefore higher navels than their European counterparts they enjoy almost a 3% hidden height advantage while sprinting
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In the pool, meanwhile, whites have the advantage because they have longer torsos, making their belly-buttons lower in the general scheme of body architecture.

"Swimming is the art of surfing the wave created by the swimmer," said Bejan.

"The swimmer who makes the bigger wave is the faster swimmer, and a longer torso makes a bigger wave. Europeans have a three-percent longer torso than West Africans, which gives them a 1.5-percent speed advantage in the pool," he said.