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Running marathons can damage unfit runners' hearts

Running marathons can damage the hearts of less fit runners Recovery can take three months

Running a marathon is often seen as the ultimate goal of out-of-condition people who decide to get fit. But is seems that completing this arduous task can do more harm than good, according to a new study from the Heart and Stroke Foundation in Canada.

By using magnetic resonance imaging (MRI) to measure the effects of long-distance running on the heart, the scientists found that segments of the heart can be damaged during the course of a marathon. The heart is composed of 17 such segments. When one segment is damaged, its neighbours can take over its function, a result which can mask the damage from conventional measurement techniques, and even make the heart appear stronger than it would be normally.

MRI scans however show that the damaged segments are more widespread and significant in the cases where the runner is less fit than a well-trained athlete. During the marathon, there were signs that the heart might be at greater risk of damage in these cases than for runners who had better training or at least had better exercise capacity.

"Without proper training, marathon running can damage your heart. Fortunately the exercise-induced injury is reversible over time," said study leader Dr. Eric Larose. "But it could take up to three months to completely recover."

Commenting on the results, he said that "...this may be an important adaptive survival mechanism, like the way the brain can switch function after a stroke - unfortunately, as a result, the data produced by traditional means (of measuring heart health) may be inconsistent and misleading."

The study suggests that anyone planning to run a marathon should ensure that they have the necessary levels of heart and lung fitness before attempting it.

The study was presented at the Canadian Cardiovascular Congress 2010.

This article was published on Mon 25 October 2010

Image © Skogas -

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