Study: Endurance races may temporarily damage heart

Marathon runners and others engaging in extreme endurance exercise may temporarily damage the right ventricle of their hearts, researchers found.

The impact on the ventricle, one of the four chambers involved in pumping blood around the body, was reversed after a week in most of the 40 athletes who took part in a study published in the European Heart Journal. Five of them showed more lasting damage, the researchers found.

Scientists led by Andre La Gerche, a research fellow at the University of Melbourne's St. Vincent Hospital, set out to probe the link between endurance exercise and heart function in a group of elite athletes in Australia who planned to compete in one of four sporting events: a marathon, an endurance triathlon, an alpine cycling race or an ultra-triathlon.

They found that in most athletes, “the heart rebuilds in a manner such that it is more capable of sustaining similar exercise stimulus in the future,” La Gerche, who is based at the University Hospitals Leuven in Belgium, said in a statement. “The question is whether there are some athletes in whom extreme exercise may cause injury from which the heart does not recover completely.”

The study participants trained for more than 10 hours a week and had no known heart problems. They agreed to undergo magnetic resonance imaging, blood tests and echocardiography a few weeks before the race, immediately after the event and six to 11 days later.

Right after the race, the athletes' hearts had changed shape, with volume increasing and the function of the ventricle decreasing, the study found. The five athletes whose hearts hadn't fully recovered in the last test showed signs of scarring known as fibrosis, and they had been training and competing for longer than the others, the researchers said.

The findings shouldn't be seen as an indication that endurance exercise is unhealthy, the researchers wrote.