Fitness fanatics should do “just one or a few” marathons or full-distance triathlons, say the cardiologists, because over-exerting the heart for years can lead to long-term damage.
There is now convincing evidence that repeatedly asking the heart to pump “massive” volumes of blood, for hours at a time, can lead to an array of problems, they say.
These include overstretching of the organ’s chambers, thickening of its walls and changes to electrical signalling. These could trigger potentially dangerous heart rhythm problems.
“In addition, long-term excessive exercise may accelerate aging in the heart, as evidenced by increased coronary artery calciﬁcation, diastolic ventricular dysfunction, and large-artery wall stiffening,” they write in the journal Heart.
Dr James O’Keefe and Carl Lavie, from St Luke’s Mid America Heart Institute in Kansas City, and the Pennington Biomedical Research Centre in Baton Rouge, US, say the heart is only designed for “short bursts” of intense activity.
They cite the example of Micah True, the hero of the book Born to Run about ultra-endurance running.
He died in March, aged 58, on a 12-mile training run in New Mexico. He routinely ran a marathon a day, sometimes more.
They believe that decades of such exertion led him to develop Phidippides cardiomyopathy.
Named after the original runner, who died delivering news of the Greeks’ victory at Marathon, it is “the constellation of cardiac pathology that has been in observed in the hearts of some veteran extreme endurance athletes”.
They concluded that most people should limit vigorous exercise to 30 to 50 minutes a day.
“If one really wants to do a marathon or full-distance triathlon etc, it may be best to do just one or a few and then proceed to safer and healthier exercise patterns,” they advise.
No amount light to moderate exercise is harmful, they note.
“A routine of moderate physical activity will add life to your years, as well as years to your life.
“In contrast, running too fast, too far, and for too many years may speed one’s progress towards the ﬁnish line of life.”
Ellen Mason, senior cardiac nurse at the British Heart Foundation, said: “Whether you’re taking part in an endurance event, watching your weight or staying healthy after a heart attack, it’s important to build up your activity levels gradually, especially if you’ve not exercised in a while.”