Study unravels why great sprinters are of African origin
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Last Updated: Monday, July 12, 2010, 18:46
Washington: Ever wondered why world's swiftest sprinters like Usain Bolt or Michael Johnson are all of West African ancestry? Scientists say it's because they have "a higher centre of gravity" compared to their white peers.

Using laws of locomotion, researchers at the Duke University found that black sprinters have a 0.15 second advantage over their white rivals because they tend to have a higher centre of gravity, meaning they can fall to the ground more quickly between each stride.

Conversely, having a lower then average centre of gravity helps white swimmers because their speed is determined by the height they can get above water, they found.

In a paper published in the International Journal of Design and Nature and Ecodynamics, Duke professor Adrian Bejan and co-authors Edward Jones of Cornell University and Duke graduate Jordan Charles explained that centre of gravity tends to be located higher on the body of blacks than whites.

The researchers, who looked at elite athletes over the past 100 years for their study, believe that these differences are not racial, but rather biological.

"There is a whole body of evidence showing that there are distinct differences in body types among blacks and whites," said Jones, who specialises in adolescent obesity, nutrition and anthropometry, the study of body composition.

"These are real patterns being described here -- whether the fastest sprinters are Jamaican, African or Canadian -- most of them can be traced back generally to Western Africa."

Usain Bolt is a Jamaican sprinter and a three-time Olympic gold medalist, who holds the world record for the 100 metres and the 200 metres. Johnson, a retired American sprinter, have won four Olympic gold medals and was crowned world champion eight times.

Swimmers, Jones said, tend to come from Europe, and therefore tend to be white. He also pointed out that there are cultural factors at play as well, such as a lack of access to swimming pools to those of lower socioeconomic status.

It all comes down to body makeup, not race, said Bejan said.

"Blacks tend to have longer limbs with smaller circumferences, meaning that their centres of gravity are higher compared to whites of the same height," Bejan said.

"Asians and whites tend to have longer torsos, so their centres of gravity are lower."

Using this difference in body types, the researchers calculated that black sprinters are 1.5 per cent 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 centre 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.”

"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 centre of gravity. For the fastest swimmers, longer torsos allow the body to fall forward farther, riding the larger and faster wave."

This analysis was supported by the National Science Foundation.


First Published: Monday, July 12, 2010, 18:46

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