Marathon running can damage a heart

3 min read

Training is the best protection

Running 26.2 miles is not for the faint of heart.

Abnormalities in heart structure and function were found in men and women who ran the Boston Marathon in 2004 and 2005 by Harvard Medical School researchers.

For some 2,500 years, scientists have written about possible unhealthy outcomes of running for tens of miles when nothing is chasing you. But more and more people are doing it. In 2005, 382,000 runners completed a marathon, 80,000 more than in 2000. That has not led to a massive increase in heart attacks. In fact, Arthur Siegel, an assistant clinical professor of medicine, says the risk of dying from a heart attack is a scant one in 50,000 runners.

Still, through the ages, scientists have worried about, and actually found evidence for, disheartening damage from such exertion. This concern motivated Malissa Wood, a cardiologist at Harvard-affiliated Massachusetts General Hospital, to lead a study to get some better answers to the vexing question. “To our knowledge, our study is the first to successfully correlate participation in endurance sports with evidence of cardiac injury and dysfunction after marathon running,” she notes.

Wood has first-leg knowledge of what she studies. She has completed four marathons, covering the 26.2 miles in as little as three hours and 46 minutes.

Wood, Siegel, Tomas Neilan, and their colleagues at Harvard and Duke university teaching hospitals recruited 60 marathoners with no history of heart disease. Forty-one men and 19 women kept logs of their training schedule starting four months prior to the race. They also submitted to blood tests and sound imaging (echocardiograhy) to determine the before-and-after health of their hearts. They ran the 26.2 miles in times ranging from about three to six hours; the average time was four hours and five minutes.

Training a heart

The sound scans and blood tests showed definite signs of heart stress, but no evidence that heart cells died from the running. Heart chambers experienced some difficulty refilling after pumping blood out. Abnormalities also occurred in pumping of blood from the right side of the heart to the lungs. Runners’ heartbeats increased by 40 beats a minute, and they lost an average of 3 pounds.

None of these changes, however, caused any medical problems during or immediately after the race. Also, “There is no data to suggest that any long-term aftereffects were caused by the changes,” Wood notes.

The most important finding is that any worrisome evidence of possible dysfunction turned out to be most pronounced in runners who spent the least time in training. Those who prepared by running 45 miles or more a week exhibited much fewer signs of heart stress than people who ran 35 miles a week or less.

“The biggest message of our study is that you should train wisely and well before taking on a marathon,” Wood comments. That message also applies to athletes who participate in other endurance sports such as cycling and rowing, she adds.

Wood and her colleagues plan to continue their studies of the marathoner’s heart by monitoring some of the elite runners in the 2007 Boston Marathon.

The Wood team describes these tests and results in detail in the Nov. 28 issue of Circulation, a journal of the American Heart Association. Both the report and an editorial comment on it mention the “on the other hand” aspect of endurance exercising – namely, extensive evidence exists that it is associated with a reduction in the risk of heart disease and an increase in life expectancy.

To take advantage of such benefits, and avoid any breaking of a marathoner’s heart, Wood advises, “Train appropriately. Use your head when you use your heart.”