Jan. 22, 2007 — Most athletes pay a physical price for their love of the sport, but the ones who engage in endurance sports may be pushing their bodies to the brink of heart failure, according to a new study.

That's because the physical wear and tear of years of heavy-duty workouts appear to weaken the heart muscle predisposing an athlete to a rare, but potentially deadly, condition called ventricular arrhythmia in which the heart beats erratically.

"There may be a limit to how much exercise the heart can tolerate," said Hein Heidbuchel, a cardiologist at University Hospital Gasthuisberg at the University of Leuven in Belgium, and the author of the paper.

Researchers have known for some time that high-level athletes, like the cyclists who compete in the Tour de France, are susceptible to ventricular arrhythmia. What they didn't know was whether the irregular heartbeats were a result of a genetic flaw, or the product of over-training.

In this study, Heidbuchel and his team examined the heart function of a group of 22 athletes with ventricular arrhythmia, and compared it to the heart function of 15 healthy endurance athletes and a control group of 10 non-athletes. Most of the athletes were cyclists, with a handful of runners, kayakers, and footballers thrown in. All were Dutch and Belgian men aged 18 to 55.

The tests showed that in 18 of the 22 sportsmen with the heart problem, the irregular heartbeat originated in the right chamber or ventricle of the heart. Moreover, the structural weakness resulted in their hearts pumping less blood out of the right chamber than was the case in the healthier athletes.

"Lifelong endurance training may lead to heart disturbances, particularly in young male athletes," he said.