Running marathons could permanently damage the hearts of some endurance athletes, scientists believe.
New research suggests extreme physical activity can scar the right ventricle of the heart in susceptible individuals.
Athletes taking part in high-endurance activities such as marathons, triathlons, or alpine cycling could be at risk without knowing it.
Scientists in Australia and Belgium studied 40 elite athletes who were planning to compete in one of four endurance events. All were highly trained top performers with no known heart problems.
Test results showed that immediately after racing the athletes’ hearts had changed shape, growing in volume, while right ventricle function decreased.
The right ventricle, one of the heart’s four chambers, pumps blood to the lungs.
Right ventricle function recovered in most athletes after a week, but in five there was evidence of potentially permanent scarring.
Study leader Andre La Gerche, from the University of Melbourne, Australia, said: “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.”
“Our study identifies the right ventricle as being most susceptible to exercise-induced injury and suggests that the right ventricle should be a focus of attention as we try to determine the clinical significance of these results. Large, prospective, multi-centre trials are required to elucidate whether extreme exercise may promote arrhythmias in some athletes. To draw an analogy, some tennis players develop tennis elbow. This does not mean that tennis is bad for you; rather it identifies an area of susceptibility on which to focus treatment and preventative measures.”
Sanjay Sharma, professor at St George’s University London, medical director of the London Marathon, called for more research looking at larger groups of endurance athletes.
He added: “My personal feeling is that extreme endurance exercise probably does cause damage to the heart in some athletes.”