VIENNA, Austria -- Riding the grueling Tour de France bike
race takes strength, stamina -- and perhaps a heart nearly 40
percent bigger than normal.
Researchers who examined the hearts of former Tour bikers found
that the athletes' hearts were from 20 to 40 percent larger than
average, said Dr. Francois Carre of the Centre Hospitalier
Universitaire de Rennes, France, speaking at a meeting of the
European Society of Cardiology.
The difference is attributable largely to rigorous training that
expands the cyclists' hearts. But researchers have not yet
determined whether the athletes' hearts were larger to begin with.
"They are a special breed," said Dr. Richard Becker, a
professor of medicine at Duke University and spokesman for the
American Heart Association. Becker was not connected to Carre's
Scientists have long noticed the phenomenon of the "athlete's
heart." Athletes who train hard in aerobic sports, such as
cycling, running or swimming, tend to have a bigger heart that
pumps more blood throughout the body.
The heart's walls become thicker to be able to handle the
increased blood volume. That gives the athletes an edge by
increasing their oxygen levels and improving their endurance.
Carre's study, funded by the Brittany provincial government in
France, is perhaps the first to track what happens to athletes'
hearts when they stop training.
Medical tests done on all Tour de France cyclists before the
race begins showed virtually all have enlarged hearts, Carre said.
"When you see an athlete's heart test, you know right away that
it's not a normal person," he said.
In his study, Carre tracked seven former professional cyclists
through their final year of competition and three years of
Once a year, the cyclists took tests to check the size and
function of the heart. They were also tested on their fitness
Carre found that the athletes' hearts shrank nearly a quarter in
size after they finished riding professionally. Still, the cyclists
remained in excellent physical condition.
"Some athletes have a genetic predisposition to perform
better," Carre said. "But we found that in these cyclists, their
hearts adapted to the hard training conditions by just getting
The intense training that Tour de France athletes undergo to
race in a three-week-long competition cycling up and down mountains
is arguably among the toughest in professional sports.
"When you examine Tour de France athletes, they are probably
among the best-trained athletes in the world," said Dr. Alfred
Bove, a physician for the Philadelphia 76ers basketball team and
vice president of the American College of Cardiology. "This study
shows us that even in extreme conditions, the body finds a way to
Bove said that in athletes with bigger hearts, doping could
prove potentially more dangerous than for normal people.
Athletes with bigger hearts have more red blood cells, which
deliver oxygen around the body. These cells are thicker than normal
cells. So if athletes decide to use an illegal agent like the
blood-booster EPO, they run the risk of making their blood too
thick. That puts them in danger of a clot, stroke, or heart attack.
"These athletes already have hearts that have increased in
volume to adapt to their training workload," Bove said. "If they
then go and use drugs, that could potentially erase the natural
advantage they already have."