Marathon Running Can Tax the Heart

Less-Fit Runners Could Develop Temporary Damage to the Heart During a Marathon, Study Finds

Reviewed by Laura J. Martin, MD on October 25, 2010

Oct. 25, 2010 -- Runners who are less fit may experience temporary but reversible damage to the heart during a marathon, according to a new study.

Marathon running can cause temporary increases in swelling and inflammation of the heart muscle, as well as decreases in blood flow, and the less physically fit the runner, the more widespread this damage. That’s according to new research presented at the Canadian Cardiovascular Congress 2010 in Montreal.

"There is no permanent damage to the heart, but there is some temporary, reversible damage that occurs during the run," says study author Eric Larose, a cardiologist at the Quebec Foundation for Health Research in Quebec City, Canada. Heart function returns to baseline in three months, he says.

Twenty marathon runners underwent magnetic resonance imaging (MRI) exams of their hearts, blood tests, and exercise testing in the six to eight weeks before the race and again two days after the marathon.

The runners in the new study were considered low-risk. "If we are finding this in low-risk runners, people who haven't been given a clean bill of health should reconsider running a marathon," he says. "To get healthy you don't need to run a marathon, but to run a marathon you do need to be healthy.

"Exercise is great to prevent cardiovascular disease in the long run, but while you are exercising -- particularly vigorously -- your risk of an event can go up," he says.

More to Heart-Healthy Exercise Than Marathon Running

"This is very exciting research that confirms clinical suspicion that some people don't do well with marathons," saysBeth Abramson, MD, a spokeswoman for the Heart and Stroke Foundation of Canada and director of the Cardiac Prevention Center at St. Michael’s Hospital in Toronto.

"Bursts of extreme activity may be transiently harmful on the heart," she says. "If you are planning to run a marathon, talk to your doctor and make sure you train with someone who knows what they are doing.

"You don’t have to run a marathon to be physically fit and lead a heart-healthy life," she says. Aiming for 30- 60 minutes of exercise most days of the week can improve cardiovascular health, she says.

Proper Training Is Essential for Marathon Runners

The New York City marathon is around the corner, and about 40,000 runners are expected to run. As long as they train appropriately and get clearance from a doctor, they should be OK, says Lewis G. Maharam, MD, the medical director of the Rock ‘n’ Roll Marathon series and a sports medicine doctor in New York.

"The heart is a muscle, and the better trained you are for the distance, the better the muscle is equipped to handle the distance," he says.

"Respect the distance and train for the distance," he advises. "Have an annual checkup and tell your doctor what exercise you plan to do as far as intensity and length," he says.

This is important. "If you say I am training to run the New York City marathon in seven hours, they will look at you differently and may do different tests to assess your cardiac fitness to do the event," he says.

The International Marathon Medical Directors Association recommends taking a baby aspirin on the day of the race to lower heart risks (assuming aspirin is advisable) and limiting caffeine to less than 200 milligrams before or during the race.

That said, marathon running is not for everyone. "If you are not appropriately trained and screened, you should not run," Maharam says.

This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.

Show Sources


Canadian Cardiovascular Congress 2010, Montreal, Oct. 23-27, 2010.

Eric Larose, MD, cardiologist, Quebec Foundation for Health Research, Quebec City, Canada.

Beth Abramson, MD, spokeswoman, Heart and Stroke Foundation of Canada; director, Cardiac Prevention Center, St. Michael’s Hospital, Toronto.

Lewis G. Maharam, MD, medical director, Rock 'n' Roll Marathon series; sports medicine doctor, New York.

International Marathon Medical Directors Association: "Health Recommendations for Runners and Walkers."

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