Healthy living

Marathon running could damage the heart

marathon running Some more susceptible than others, study suggests

People who take part in endurance sports such as marathons or triathlons could damage their heart, according to research.

A new study of 40 athletes found their hearts had changed shape, increased in size and had signs of excessive stretching of heart muscle after taking part in an endurance sporting event. Some athletes' hearts also had signs of permanent scarring.

However, the UK and Belgian researchers were quick to stress that the athletes trained for extreme endurance events such as marathon running, triathlons, ultra-triathlons and alpine cycling, and the risk of heart damage for most people participating in endurance sport is low.

Some 40 elite Australian athletes in training for endurance events took part in the study. All trained intensely, for more than 10 hours a week, and had no known heart problems.

Heart and blood tests and an MRI scan were carried out two to three weeks before the race, immediately after it and six to eleven days after the event.

Immediately after the race the tests showed that most of the athletes' hearts had changed shape and increased in size, while function decreased in the right ventricle - one of the four chambers of the heart involved in pumping blood around the body.

The changes to the function of the right ventricle also increased with the duration of the race.

In contrast, the left ventricle, which has been the most studied in athletes, showed no changes.

Levels of a chemical called B-type natriuretic peptide (BNP), secreted by the heart ventricles in response to excessive stretching of heart muscle, also increased.

In most of the athletes, the right ventricle function returned to normal after a week, but MRI scans detected signs of scarring in five of the athletes, which is irreversible. The five athletes had been training and competing for longer than the others, the researchers said.

Dr André La Gerche, from the University Hospitals Leuven, Belgium, said: "It is most important that our findings are not over-extrapolated to infer that endurance exercise is unhealthy. Our data do not support this premise.

"Virtually all of the changes in the athletes’ hearts had resolved one week after having taken part in a competitive event.

"In most athletes, a combination of sensible training and adequate recovery should cause an improvement in heart muscle function; that is, the heart rebuilds in a manner such that it is more capable of sustaining a similar exercise stimulus in the future. This positive training response can be over months rather than weeks.

However, he also said that the findings suggested that some athletes may be more susceptible to developing heart damage as a result of long-term endurance exercise.

Professor Sanjay Sharma, of St George’s University London, and medical director of the London Marathon, said: "My personal feeling is that extreme endurance exercise probably does cause damage to the heart in some athletes.

"I don’t believe that the human body is designed to exercise at full stretch for as long as 11 hours a day, so damage to the heart is not implausible.

"It is too early to say that taking part in endurance sports causes long-term damage to the right ventricle, but this study is an indication that it might cause a problem in some endurance athletes with a predisposition and, therefore, it should be studied further."

The study findings are published in the European Heart Journal.

This article was published on Wed 7 December 2011

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