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Science, Vol 305, Issue 5684, 637-639 , 30 July 2004

Peering Under the Hood of Africa's Runners

Constance Holden

Kenyans dominate endurance running, and West Africans excel as
sprinters. With a physiological explanation in hand, researchers are now
probing the genetics of this geographic mastery

http://www.sciencemag.org/cgi/content/full/sci;305/5684/637

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- Tony

Tony qtrader2@(remove)hotmail.com said:

This site wants a login, can you post it?

Quoted message said:

- Tony

That's strange. I was able to read it without any login.
Anyway, I guess I'll just post it here. (210+ lines to follow.)

They also have a PDF version here:

http://www.sciencemag.org/cgi/reprint/305/5684/637.pdf

So you could try that.
In any case, the text is the same as I paste
below except for a couple of pictures.

----------------------

Peering Under the Hood of Africa's Runners
Constance Holden

Kenyans dominate endurance running, and West Africans excel as
sprinters. With a physiological explanation in hand, researchers are now
probing the genetics of this geographic mastery.

In 1968, a Kenyan runner named Kip Keino emerged as a shining star of
the Mexico City summer Olympics, setting a world record in the
1500-meter race. Year after year Keino's success has been followed by
equally dazzling feats by his compatriots: Kenyan men now hold world
records in the 3000-meter track race, the 15-, 20-, and 25-kilometer
road races, the half-marathon, and the marathon. Kenyan men have won 13
of the last 14 Boston marathons. Kenyan women are also rising fast: They
hold half of the top 10 marathon times and world records in 20-, 25-,
and 30-km track races. What is even more remarkable is that most of
these athletes come from a small area in Kenya's Rift Valley, from a
group of tribes called the Kalenjin who number little more than 3
million people.

Theories abound about what Kenya-born writer and runner John Manners
calls "the greatest geographical concentration of achievement in the
annals of sport." Is it the high altitude that fosters big lungs and
efficient oxygen use? Is it their maize-based diet? Or the fact that
many children run to school? A grueling training regimen, perhaps?

Such questions have inspired a handful of researchers to try to define
the Kenyan magic. Meanwhile, scientists are unraveling why athletes
whose ancestors come from the other side of the continent--West
Africa--have emerged as the world's fastest sprinters.

Fuel economy
Leading the charge in penetrating the Kenyan mystique has been Bengt
Saltin, a Swedish physiologist who heads the Copenhagen Muscle Research
Centre in Denmark. In the 1990s, Saltin's group began comparing Kenyan
and Scandinavian runners by scrutinizing their physiological makeups
and assessing the "trainability" of novice runners in both countries.

A decade later, the scientists have ruled out most of the popular
explanations for Kenyans' domination of running. Altitude is not the
key to the riddle, they have found, because there's no difference
between Kenyans and Scandinavians in their capacity to consume oxygen.
And the Kenyan diet is on the low side for essential amino acids and
some vitamins as well as fat, says Dirk Christensen of the Copenhagen
center: "In spite of the diet, they perform at high level." The
running-to-school hypothesis was demolished as well: Kenyan children
aren't any more physically active than their Danish peers. Do Kenyans
try harder? The researchers found that the Danes actually pushed
themselves harder on a treadmill test, reaching higher maximum heart
rates.

An important clue is the ability of Kenyans to resist fatigue longer.
Lactate, generated by tired, oxygen- deprived muscles, accumulates more
slowly in their blood. Comparisons of lactate levels have suggested to
Saltin's group that Kenyan runners squeeze about 10% more mileage from
the same oxygen intake than Europeans can.

Just as more aerodynamic cars get better gas mileage, the Kenyan build
helps explain their fuel efficiency. A recent British TV documentary
described the Kalenjin as possessing "birdlike legs, very long levers
that are very, very thin [on which they] bounce and skip" along.

Saltin's group has quantified this observation. Compared with Danes,
the thinner calves of Kenyans have, on average, 400 grams less flesh
in each lower leg. The farther a weight is from the center of gravity,
the more energy it takes to move it. Fifty grams added to the ankle
will increase oxygen consumption by 1%, Saltin's team calculates. For
the Kenyans, that translates into an 8% energy savings to run a
kilometer. "We have solved the main problem," declares Henrik Larsen
of the Copenhagen center. "Kenyans are more efficient because it takes
less energy to swing their limbs." Other scientists say the jury is
still out on the Kenyan question. But "I think Saltin is probably the
most correct that anyone is at the moment," says physiologist Kathryn
Myburgh of the University of Stellenbosch in South Africa, who is
exploring the role of Kenyans' training.

However, slim lower legs are not the whole story. Kenyan runners also
have a higher concentration of an enzyme in skeletal muscle that
spurs high lactate turnover and low lactate production. Saltin says
that this results in an "extraordinarily high" capacity for fatty
acid oxidation, which helps wring more energy out of the muscles'
biochemical reactions. Because intense training alters the body's
biochemistry, Saltin says that he can't say for sure whether the
ezyme levels are due to genes or training. But he adds, "Ithink it's
genetic."

Research in South Africa jibes with the Copenhagen group's findings.
A team led by exercise physiologist Adele Weston of the University of
Sydney, Australia, compared black South Africans, whose running
strengths are similar to those of Kenyans, with white runners. The
two groups had similar VO2 max values--that is, when putting out
maximum effort, they used up the same amount of oxygen per kilogram
of body weight per minute. But the black runners were more efficient
in their oxygen consumption, lasting on a treadmill at maximum speed
for twice as long as the whites. As with the Kenyans, the black South
African runners accumulated less lactate and had higher levels of key
muscle enzymes.

A little more twitchy
Whereas East Africans dominate long- distance running, West Africans
have surged to the fore in short-distance events. Little research has
been done on West Africans, but there's powerful circumstantial
evidence for some physical advantages, as presented by Jon Entine in
his book Taboo: Why Black Athletes Dominate Sports and Why We're
Afraid to Talk About It. Athletes of primarily West African
descent--which includes the majority of U.S. blacks--hold all but six
of the 500 best times in the 100-meter race, "the purest measure of
running speed," says Entine, whose book set off a broad debate on the
subject.

Various studies have shown that West African athletes have denser
bones, less body fat, narrower hips, thicker thighs, longer legs, and
lighter calves than whites. But the differences between East and West
Africans are even more striking. The fabled Kenyan runners are small,
thin, and tend to weigh between 50 and 60 kilograms, whereas West
African athletes are taller and a good 30 kilograms heavier, says
Timothy Noakes, a prominent exercise physiologist and researcher at
the University of Cape Town.

The differences don't stop with body shape; there is also evidence
of a difference in the types of muscle fibers that predominate.
Scientists have divided skeletal muscles into two basic groups
depending on their contractile speed: type I, or slow-twitch
muscles, and type II, fast-twitch muscles. There are two kinds of
the latter: type IIa, intermediate between fast and slow; and type
IIb, which are superfast-twitch. Endurance runners tend to have
mostly type I fibers, which have denser capillary networks and are
packed with more mitochondria. Sprinters, on the other hand, have
mostly type II fibers, which hold lots of sugar as well as enzymes
that burn fuel in the absence of oxygen. In the 1980s, Claude
Bouchard's team at Quebec's Laval University took needle biopsies
from the thigh muscles of white French Canadian and black West
African students. They found that the Africans averaged
significantly more fast-twitch muscle fibers--67.5%--than the French
Canadians, who averaged 59%. Endurance runners have up to 90% or
more slow-twitch fibers, Saltin reports.

Bouchard, now at Louisiana State University in Baton Rouge, says his
team looked at two enzymes that are markers for oxidative metabolism
and found higher activity of both in the West Africans, meaning they
could generate more ATP, the energy currency of the cell, in the
absence of oxygen. The study suggests that in West Africa there may
be a larger pool of people "with elevated levels of what it takes to
perform anaerobically at very high power output," says Bouchard.

Although training can transform superfast-twitch type IIb fibers
into the hybrid type IIa, it is unlikely to cause slow- and
fast-twitch fibers to exchange identities. Myburgh says there is
evidence that, with extremely intensive long-distance training, fast
IIa fibers can change to slow type I fibers. So far, however, there
is no evidence that slow-twitch fibers can be turned into
fast-twitch ones. As an athlete puts on muscle mass through
training, new fibers are not created, but existing fibers become
bigger.

Running ACEs
The differences in physique and muscle makeup that underlie the
dominance of Kenyan endurance runners and West African sprinters
doubtless have a strong genetic component. But researchers are only
just getting off the starting mark in the search for genes that
influence running performance. Bouchard's group, for example, is
collecting DNA samples from 400 runners and other top endurance
athletes from the United States and Europe, but he says they haven't
spotted any running genes yet.

There are a couple of intriguing possibilities, though. In 1999, a
team headed by Kathryn North of the Children's Hospital at Westmead
in Australia described two versions of a gene that affects
production of name-actinin-3, a protein found only in fast-twitch
muscles. They found the less efficient version of the gene--which
results in poorer energy conversion--in 18% of the members of a
group of Caucasians. In 2003, North's group reported in the American
Journal of Human Genetics that only 6% of a group of sprinters had
the gene defect; 26% of endurance runners had it. The authors
surmise that name-actinin-3 helps muscles generate "forceful
contractions at high velocity."

Alejandro Lucia Mulas of the European University in Madrid is taking
DNA samples from Eritrean runners to explore another candidate:
different versions of the gene for angiotensin-converting enzyme
(ACE). Lucia says the less active version, or I allele, of this gene
is associated with less muscle, less fluid retention, and more
relaxed blood vessels--which would enhance oxygen uptake--and
appears to be more prevalent in endurance runners.

And in Scotland, sports physiologist Yannis Pitsiladis has launched
a major onslaught on the Kenyans' secrets with the International
Centre for East African Running Science. Headquartered at the
University of Glasgow, the virtual center will bring together
research on demography, diet, and socioeconomic factors as well as
genes. Pitsiladis says he has spent the last 3 years in East Africa
collecting DNA samples from their "living legends" and now has DNA
from 404 Kenyan and 113 Ethiopian athletes. His team has found a
higher prevalence of the I allele for the ACE enzyme in male
marathoners compared with men from the general Ethiopian population.
But Pitsiladis thinks his numbers may lack significance given the
variability of the trait in African populations. "At the moment
there is no evidence" that East Africans have a genetic advantage in
running, he says.

None of the data negate the importance of cultural habits and
training. But as Entine quotes anthropologist and sports science
expert Robert Malina, who is retired from Michigan State
University, "Differences among athletes of elite caliber are so
small that if you have an advantage that might be genetically based
... it might be very, very significant."

Next month's Olympic games in Athens should demonstrate yet again
that West African runners are built for speed and Kenyans built to
endure.

Interesting article thanks.

[email hidden] wrote in message ...

Quoted message said:

Tony qtrader2@(remove)hotmail.com said:

This site wants a login, can you post it?

Quoted message said:

- Tony

That's strange. I was able to read it without any login.
Anyway, I guess I'll just post it here. (210+ lines to follow.)

They also have a PDF version here:

http://www.sciencemag.org/cgi/reprint/305/5684/637.pdf

So you could try that.
In any case, the text is the same as I paste
below except for a couple of pictures.

----------------------

Peering Under the Hood of Africa's Runners
Constance Holden

Kenyans dominate endurance running, and West Africans excel as
sprinters. With a physiological explanation in hand, researchers are now
probing the genetics of this geographic mastery.

In 1968, a Kenyan runner named Kip Keino emerged as a shining star of
the Mexico City summer Olympics, setting a world record in the
1500-meter race. Year after year Keino's success has been followed by
equally dazzling feats by his compatriots: Kenyan men now hold world
records in the 3000-meter track race, the 15-, 20-, and 25-kilometer
road races, the half-marathon, and the marathon. Kenyan men have won 13
of the last 14 Boston marathons. Kenyan women are also rising fast: They
hold half of the top 10 marathon times and world records in 20-, 25-,
and 30-km track races. What is even more remarkable is that most of
these athletes come from a small area in Kenya's Rift Valley, from a
group of tribes called the Kalenjin who number little more than 3
million people.

Theories abound about what Kenya-born writer and runner John Manners
calls "the greatest geographical concentration of achievement in the
annals of sport." Is it the high altitude that fosters big lungs and
efficient oxygen use? Is it their maize-based diet? Or the fact that
many children run to school? A grueling training regimen, perhaps?

Such questions have inspired a handful of researchers to try to define
the Kenyan magic. Meanwhile, scientists are unraveling why athletes
whose ancestors come from the other side of the continent--West
Africa--have emerged as the world's fastest sprinters.

Fuel economy
Leading the charge in penetrating the Kenyan mystique has been Bengt
Saltin, a Swedish physiologist who heads the Copenhagen Muscle Research
Centre in Denmark. In the 1990s, Saltin's group began comparing Kenyan
and Scandinavian runners by scrutinizing their physiological makeups
and assessing the "trainability" of novice runners in both countries.

A decade later, the scientists have ruled out most of the popular
explanations for Kenyans' domination of running. Altitude is not the
key to the riddle, they have found, because there's no difference
between Kenyans and Scandinavians in their capacity to consume oxygen.
And the Kenyan diet is on the low side for essential amino acids and
some vitamins as well as fat, says Dirk Christensen of the Copenhagen
center: "In spite of the diet, they perform at high level." The
running-to-school hypothesis was demolished as well: Kenyan children
aren't any more physically active than their Danish peers. Do Kenyans
try harder? The researchers found that the Danes actually pushed
themselves harder on a treadmill test, reaching higher maximum heart
rates.

An important clue is the ability of Kenyans to resist fatigue longer.
Lactate, generated by tired, oxygen- deprived muscles, accumulates more
slowly in their blood. Comparisons of lactate levels have suggested to
Saltin's group that Kenyan runners squeeze about 10% more mileage from
the same oxygen intake than Europeans can.

Just as more aerodynamic cars get better gas mileage, the Kenyan build
helps explain their fuel efficiency. A recent British TV documentary
described the Kalenjin as possessing "birdlike legs, very long levers
that are very, very thin [on which they] bounce and skip" along.

Saltin's group has quantified this observation. Compared with Danes,
the thinner calves of Kenyans have, on average, 400 grams less flesh
in each lower leg. The farther a weight is from the center of gravity,
the more energy it takes to move it. Fifty grams added to the ankle
will increase oxygen consumption by 1%, Saltin's team calculates. For
the Kenyans, that translates into an 8% energy savings to run a
kilometer. "We have solved the main problem," declares Henrik Larsen
of the Copenhagen center. "Kenyans are more efficient because it takes
less energy to swing their limbs." Other scientists say the jury is
still out on the Kenyan question. But "I think Saltin is probably the
most correct that anyone is at the moment," says physiologist Kathryn
Myburgh of the University of Stellenbosch in South Africa, who is
exploring the role of Kenyans' training.

However, slim lower legs are not the whole story. Kenyan runners also
have a higher concentration of an enzyme in skeletal muscle that
spurs high lactate turnover and low lactate production. Saltin says
that this results in an "extraordinarily high" capacity for fatty
acid oxidation, which helps wring more energy out of the muscles'
biochemical reactions. Because intense training alters the body's
biochemistry, Saltin says that he can't say for sure whether the
ezyme levels are due to genes or training. But he adds, "Ithink it's
genetic."

Research in South Africa jibes with the Copenhagen group's findings.
A team led by exercise physiologist Adele Weston of the University of
Sydney, Australia, compared black South Africans, whose running
strengths are similar to those of Kenyans, with white runners. The
two groups had similar VO2 max values--that is, when putting out
maximum effort, they used up the same amount of oxygen per kilogram
of body weight per minute. But the black runners were more efficient
in their oxygen consumption, lasting on a treadmill at maximum speed
for twice as long as the whites. As with the Kenyans, the black South
African runners accumulated less lactate and had higher levels of key
muscle enzymes.

A little more twitchy
Whereas East Africans dominate long- distance running, West Africans
have surged to the fore in short-distance events. Little research has
been done on West Africans, but there's powerful circumstantial
evidence for some physical advantages, as presented by Jon Entine in
his book Taboo: Why Black Athletes Dominate Sports and Why We're
Afraid to Talk About It. Athletes of primarily West African
descent--which includes the majority of U.S. blacks--hold all but six
of the 500 best times in the 100-meter race, "the purest measure of
running speed," says Entine, whose book set off a broad debate on the
subject.

Various studies have shown that West African athletes have denser
bones, less body fat, narrower hips, thicker thighs, longer legs, and
lighter calves than whites. But the differences between East and West
Africans are even more striking. The fabled Kenyan runners are small,
thin, and tend to weigh between 50 and 60 kilograms, whereas West
African athletes are taller and a good 30 kilograms heavier, says
Timothy Noakes, a prominent exercise physiologist and researcher at
the University of Cape Town.

The differences don't stop with body shape; there is also evidence
of a difference in the types of muscle fibers that predominate.
Scientists have divided skeletal muscles into two basic groups
depending on their contractile speed: type I, or slow-twitch
muscles, and type II, fast-twitch muscles. There are two kinds of
the latter: type IIa, intermediate between fast and slow; and type
IIb, which are superfast-twitch. Endurance runners tend to have
mostly type I fibers, which have denser capillary networks and are
packed with more mitochondria. Sprinters, on the other hand, have
mostly type II fibers, which hold lots of sugar as well as enzymes
that burn fuel in the absence of oxygen. In the 1980s, Claude
Bouchard's team at Quebec's Laval University took needle biopsies
from the thigh muscles of white French Canadian and black West
African students. They found that the Africans averaged
significantly more fast-twitch muscle fibers--67.5%--than the French
Canadians, who averaged 59%. Endurance runners have up to 90% or
more slow-twitch fibers, Saltin reports.

Bouchard, now at Louisiana State University in Baton Rouge, says his
team looked at two enzymes that are markers for oxidative metabolism
and found higher activity of both in the West Africans, meaning they
could generate more ATP, the energy currency of the cell, in the
absence of oxygen. The study suggests that in West Africa there may
be a larger pool of people "with elevated levels of what it takes to
perform anaerobically at very high power output," says Bouchard.

Although training can transform superfast-twitch type IIb fibers
into the hybrid type IIa, it is unlikely to cause slow- and
fast-twitch fibers to exchange identities. Myburgh says there is
evidence that, with extremely intensive long-distance training, fast
IIa fibers can change to slow type I fibers. So far, however, there
is no evidence that slow-twitch fibers can be turned into
fast-twitch ones. As an athlete puts on muscle mass through
training, new fibers are not created, but existing fibers become
bigger.

Running ACEs
The differences in physique and muscle makeup that underlie the
dominance of Kenyan endurance runners and West African sprinters
doubtless have a strong genetic component. But researchers are only
just getting off the starting mark in the search for genes that
influence running performance. Bouchard's group, for example, is
collecting DNA samples from 400 runners and other top endurance
athletes from the United States and Europe, but he says they haven't
spotted any running genes yet.

There are a couple of intriguing possibilities, though. In 1999, a
team headed by Kathryn North of the Children's Hospital at Westmead
in Australia described two versions of a gene that affects
production of name-actinin-3, a protein found only in fast-twitch
muscles. They found the less efficient version of the gene--which
results in poorer energy conversion--in 18% of the members of a
group of Caucasians. In 2003, North's group reported in the American
Journal of Human Genetics that only 6% of a group of sprinters had
the gene defect; 26% of endurance runners had it. The authors
surmise that name-actinin-3 helps muscles generate "forceful
contractions at high velocity."

Alejandro Lucia Mulas of the European University in Madrid is taking
DNA samples from Eritrean runners to explore another candidate:
different versions of the gene for angiotensin-converting enzyme
(ACE). Lucia says the less active version, or I allele, of this gene
is associated with less muscle, less fluid retention, and more
relaxed blood vessels--which would enhance oxygen uptake--and
appears to be more prevalent in endurance runners.

And in Scotland, sports physiologist Yannis Pitsiladis has launched
a major onslaught on the Kenyans' secrets with the International
Centre for East African Running Science. Headquartered at the
University of Glasgow, the virtual center will bring together
research on demography, diet, and socioeconomic factors as well as
genes. Pitsiladis says he has spent the last 3 years in East Africa
collecting DNA samples from their "living legends" and now has DNA
from 404 Kenyan and 113 Ethiopian athletes. His team has found a
higher prevalence of the I allele for the ACE enzyme in male
marathoners compared with men from the general Ethiopian population.
But Pitsiladis thinks his numbers may lack significance given the
variability of the trait in African populations. "At the moment
there is no evidence" that East Africans have a genetic advantage in
running, he says.

None of the data negate the importance of cultural habits and
training. But as Entine quotes anthropologist and sports science
expert Robert Malina, who is retired from Michigan State
University, "Differences among athletes of elite caliber are so
small that if you have an advantage that might be genetically based
... it might be very, very significant."

Next month's Olympic games in Athens should demonstrate yet again
that West African runners are built for speed and Kenyans built to
endure.