Too many marathons can kill

Running too many marathons in a lifetime could be dangerous for the heart and lead to an early death, U.S. medical researchers said. The heart is only designed for "short bursts" of intense activity said a study by Dr. James O'Keefe and Carl Lavie of St. Luke's Mid America Heart Institute in Kansas City, Mo., and the Pennington Biomedical Research Center in Baton Rouge, La. Marathon running forces the heart to pump massive amounts of blood for hours at a time, leading to overstretching of the heart's chambers, thickening of its walls and changes to electrical signaling, Britain's Daily Telegraph reported Thursday. "In addition, long-term excessive exercise may accelerate aging in the heart, as evidenced by increased coronary artery calci?cation, diastolic ventricular dysfunctio, and large-artery wall stiffening," the researchers wrote in their report published in the journal Heart. "... Running too fast, too far and for too many years may speed one's progress towards the ?nish line of life." The damage caused by a marathon will rapidly heal, though repeated endurance exercise can lead to scarring, The Independent reported. "If one really wants to do a marathon or full-distance triathlon ... it may be best to do just one or a few and then proceed to safer and healthier exercise patterns," the researchers said.