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
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
"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 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
"Locomotion is essentially a continual process of
"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
First Published: Monday, July 12, 2010, 18:46