If you run too many marathons, you may die sooner because the heart is designed only for short bursts of intense activity, say two cardiologists, based on their own research.
When you run a marathon (26.2 miles), you force the heart to pump massive amounts of blood for hours. This can overstretch the heart's chambers, thicken its walls, change its electrical signalling and accelerate its aging, said James O'Keefe, who is affiliated with St. Luke's Mid America Heart Institute in Kansas City, and Carl Lavie, of the John Ochsner Heart and Vascular Institute in New Orleans.
"Running too fast, too far and for too many years may speed one's progress toward the ?nish line of life," they wrote in an editorial in the British medical journal Heart.
Drs. O'Keefe and Levie were authors of a study published June 2012 in Mayo Clinic Proceedings, "Potential Adverse Cardiovascular Effects From Excessive Endurance Exercise." That study concluded that more investigation is needed to discover why, in some people "long-term excessive endurance exercise may induce pathologic structural remodeling of the heart and large arteries."
Little promotes health better than vigorous aerobic exercise. A study of 52,600 people over three decades indicated the death rate for runners is 19 percent lower than for non-runners.
But you can have too much of a good thing, said Drs. O'Keefe and Lavie. That same study indicated the mortality advantage vanishes for those who run more than 20 to 25 miles a week. The mortality advantage also disappears for those who run faster than 8 miles an hour, according to another study they cited in the Heart editorial.
Dr. O'Keefe, 56, is a former triathlete who used to push himself well beyond the 30 to 50 minutes of vigorous exercise a day he now says is about all most people can do safely. He cut back a few years ago when he suspected his workout routine was aging him prematurely. He now rarely runs longer than 5 kilometers (3.2 miles) and always runs slower than 8 minutes a mile.
Two area physicians who run marathons expressed skepticism.
The opinions Drs. O'Keefe and Lavie expressed in their editorial overreach the data, said Vonda Wright, director of the Performance and Research Initiative for Masters Athletes at UPMC Sports Medicine.
The population they wrote about in their editorial is far too small from which to draw such sweeping conclusions, Dr. Wright said. Unless you are constantly running marathons and ultramarathons, you have little to worry about.
"The real danger is sedentary living," she said. "If you live like the 13 million Americans who run marathons, you'll live a longer, healthier life than if you don't get enough exercise."
The dangers Drs. O'Keefe and Lavie describe are limited to a very small, very specific subgroup, said Moira Davenport, who practices sports medicine and emergency medicine at Allegheny General Hospital.
"The average person who has running a marathon on his bucket list is not who they are talking about," Dr. Davenport said.
The literature presents a more complex picture than does the editorial, she said.
Many of the changes in a runner's heart are good, Dr. Davenport said. "You end up with a more efficient heart, a lower resting heartbeat."
And most of the changes Drs. O'Keefe and Lavie decry diminish or disappear when athletes cut back on their workouts, she said.
Moderation in all things is good advice, said Drs. Wright and Davenport. The editorial should have been more moderately expressed, they said.
Jack Kelly: email@example.com or 412-263-1476.