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 percent 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. 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 study.
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 bigger hearts that pump more blood.
The heart’s walls thicken to handle the increased blood volume. That gives the athletes an edge by increasing oxygen levels and improving endurance.
Carre’s study, paid for by the Brittany provincial government in France, may be 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 had 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 retirement. Once a year, the cyclists took tests to check the size and function of the hearts. They were also tested on their fitness levels.
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 bigger.”