Bejan and Jones cite past studies of the human body which found that on average, the center of gravity is about three percent higher in blacks than whites. Using this difference in body types, the researchers calculated that black sprinters are 1.5 percent faster than whites, while whites have the same advantage over blacks in the water. The difference might seem small, Bejan said, but not when considering that world records in sprinting and swimming are typically broken by fractions of seconds.
The center of gravity for an Asian is even more advantageous to swimming than for a white, but because they tend not to be as tall, they are not setting records, Bejan said.
"Locomotion is essentially a continual process of falling forward," Bejan said. "Body mass falls forward, then rises again. Mass that falls from a higher altitude falls faster. In running, the altitude is set by the location of the center of gravity. For the fastest swimmers, longer torsos allow the body to fall forward farther, riding the larger and faster wave."
The researchers said this evolution of body types and increased speeds can be predicted by the constructal theory, a theory of natural design developed by Bejan that explains such diverse phenomena as river basin formation and basis of animal locomotion (www.constructal.org).
Jones said that the differences in body densities between blacks and whites are well-documented, which helps explain other health differences, such as the observation that black women have a lower incidence of osteoporosis than white women because of the increased density of their bones.
Jones notes that cultural issues can play a role in which form of athletic competition someone chooses, and therefore might excel in.
"When I grew up in South Carolina, we were discouraged from swimming," said Jones,
|Contact: Richard Merritt|