A new study has found marathon runners suffer temporary heart damage during the 26.2 mile (42.2km) event, which may explain the rare instances of deaths during races, LiveScience reported Monday.
The study headed up by Eric Larose of the Graduate Institute of Cardiology and Respiratory Medicine Quebec and Universite Laval in Quebec City found that while the damage was considerable during a race, it was reversible.
"We know that regular exercise reduces cardiovascular risk by a factor of two or three in the long run, but while we’re doing vigorous exercise such as marathon running, our cardiac risk increases by seven," Larose said.
Larose was running in a marathon in the 1999 Quebec City Marathon when a younger runner close to him in the pack collapsed and died near the finish line.
The incident prompted he and his colleagues to recruit 20 runners in the 2008 Quebec City Marathon, ranging in age from 21 to 55, to work out why an otherwise healthy person would die during a marathon.
The results showed that during the race, over half of the segments of the heart lose function due to an increase in inflammation and a decrease in blood flow through the muscle.
"This is the first potential explanation as to why a runner has increased risk while he’s running or she’s running," Larose said.
Within three months of running, the damage had generally disappeared.
And while Larose said the risk of dying while running a marathon was still very low, he warned: "People should not enter a marathon lightly. Training needs to be well done. You can’t cheat the marathon."