Marathon runners who are less fit or lack the proper training can impair their heart with the stress of long-distance running, new Canadian research, presented on October 25, shows.
But the good news is, injury to the cardiovascular muscles for most runners is temporary and reversible, says cardiologist Dr. Eric Larose, a professor of medicine at Laval University in Québec City.
Larose, who is a runner himself, became interested in how the heart coped with the pressure of endurance running after seeing a 20-something fellow participant collapse and die during a marathon in Quebec City years ago. He wanted to know what caused a seemingly healthy runner to have a heart attack during a race or shortly after crossing the finish line.
He presented his team’s findings at the Canadian Cardiovascular Congress 2010 in Montreal. The scientific gathering, co-sponsored by the Heart and Stroke Foundation and the Canadian Cardiovascular Society, runs till Wednesday.
Marathon runners take heart tests
For the study, Larose and his team gathered 20 marathon runners who intended to join the 2008 Quebec City Marathon. The athletes, 70% of whom were men, ranged in age from 21 to 55 years. Some were first timers; others had experience racing in several marathons.
Six to eight weeks before the marathon, the runners’ fitness levels underwent a thorough evaluation. They took a stress test called the VO2 max (or maximal oxygen uptake), which measures aerobic endurance and the body's oxygen consumption using treadmills or stationary bikes. They also had blood tests and magnetic resonance imaging (MRI) scans to measure overall heart function.
The runners repeated all the tests immediately after the race, and again for the third time three months later.
Pre-marathon test results showed that the runners with less experience and preparation had a lower VO2 max, or a lower exercise capacity.
Immediately after the race, all the runners, save for the fittest athlete in the study group, recorded varying degrees of decreased function in more than half of the 17 segments in the left ventricle, the heart's main pumping chamber. The lower functioning may be due to increased inflammation and reduced blood flow through the heart muscles.
"This is the first potential explanation as to why a runner has increased risk while he's running or she's running," says Larose.
The damage to the heart was more pronounced in those who were less prepared and less fit. "Compared to those runners with better training, they became more dehydrated and their hearts showed greater signs of injury," notes Larose. The less well-trained runners also experienced greater loss of function associated with lower blood flow and greater irritation of heart segments.
Runners' hearts recover within three months
Larose stresses, however, that the damage is not permanent. At their three-month checkups, the runners' hearts were back to normal functioning.
People should not enter a marathon lightly, he adds. "Without proper training, marathon running can damage your heart. Fortunately the exercise-induced injury is reversible over time. But it could take up to three months to completely recover."
The findings should not discourage people from getting as physically active as they can, Larose says, even as he urges a sensible approach to exercise that does not push the body beyond endurance.
Runners need to train properly for a long time, keep their bodies hydrated, and discuss with their doctors about the exercise that is right for them, he advises.
Sources:
CTV.ca News Staff, October 25, 2010, " Marathon Running Can Temporarily Damage the Heart," Accessed October 25, 2010
October 25, 2010, "Marathoners' Hearts Hurt in Short Term: Study," CBC News, Accessed October 25, 2010
Romelda Ascutia - Romelda Ascutia is a consultant, editor, writer, and blogger. Before freelancing, she spent more than 20 years as a full-time editor for a ...
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