MONDAY, Oct. 25 (HealthDay News) -- Running a marathon can damage your heart, with more than half of the segments in the heart's main pumping chamber typically functioning a little under par during the race, a new study shows.
The good news? Other parts of the heart pick up the slack and the changes reverse within three months or fewer after the run, the researchers found. The more fit and trained a runner is, the less effect the strain of a marathon was found to have on the heart.
The findings underscore the need for adequate training, but "we aren't suggesting marathons are dangerous or that people shouldn't run," said Dr. Eric Larose, a professor of medicine at the University of Laval and a research-scholar at the Quebec Foundation for Health Research, Quebec City, Canada.
Larose is slated to present his findings Monday at the Canadian Cardiovascular Congress 2010.
For the study, Larose and his colleagues gathered 20 healthy amateur runners, average age 45, who were planning to run a marathon in about six to eight weeks.
The researchers evaluated the runners' fitness with a treadmill test that computes their measure of aerobic endurance and the body's oxygen consumption, a test called the VO2 max. They also did blood tests and scanned their hearts using MRI before the race, shortly after the race and then again three months later.
The investigators found changes immediately after the race in the left ventricle -- the heart's main pumping chamber -- which is divided into 17 segments.
"Out of these, 53 percent of the segments decreased in function during the marathon," Larose said. The decreased functioning may be due to inflammation due to exertion, he added.
But he also found that neighboring segments took up the slack, compensating for the segments that weren't functioning up to par.
Despite the lowered functioning,
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