A new study suggests marathon runners may be able to breathe a little easier about the gruelling sport's effect on their hearts.

Research at Winnipeg's St. Boniface Hospital and the University of Manitoba shows that long-distance runs can cause short-term injury to the heart, but there doesn't appear to be lasting damage.

'You'll see chemicals that are raised into your body, which are the same chemicals you would measure when you have a heart attack.'—Dr. Davinder Jassal, principal investigator

The study is the first of its kind to use "advanced cardiac imaging technology" by which MRI images show cardiac abnormalities immediately after a race.

The technology was used in conjunction with other tests to assess heart damage in 14 amateur athletes aged 18 to 40, who took part in last year's 42-kilometre Manitoba Marathon. The researchers found that biomarkers used to identify cardiac stress were elevated in all the athletes right after the race.

But principal investigator Dr. Davinder Jassal says that after a week of rest, the runners' hearts exhibited no signs of long-term damage and their blood-pumping function had returned to pre-marathon levels.

Novices should consult doctor

"You'll see chemicals that are raised into your body, which are the same chemicals you would measure when you have a heart attack," he said. "But when you use MRI of the heart, there is no permanent damage to the heart."

However, Jassal says that novices planning to run a marathon should first talk to their doctors and train appropriately because the sport does put stress on the heart.

'I can't be concerned of a heart attack as a reason why someone shouldn't run unless they have clear risk factors.'—Dr. Howard Winston, sports medicine specialist

The study confirms what Dr. Howard Winston has been telling his patients for years — that there's always a small risk of a heart attack when someone runs a marathon distance.

"The frequency is very low. I can't be concerned of a heart attack as a reason why someone shouldn't run unless they have clear risk factors, " said Winston, a specialist in sports medicine in Toronto. "It's a real freak occurrence."

It's one that happened, however, to Danny Kassap, who is one of Canada's top marathon runners. Until recently, he had no history of heart trouble. But during last year's Berlin Marathon, Kassap suddenly collapsed.

"Something bad came up. I got a heart attack during the race, so I woke up the day after in the hospital," he said.

Six months down the road, he has resumed light training and despite his experience, his long-term goal is unchanged: to compete in the 2012 Olympic Games.

By then, the Manitoba researchers might have more information that will be of interest to Kassap. They are currently planning to conduct another study, this time to determine how many marathons the heart can endure before long-term damage takes place.

The present study was published in this week's American Journal of Cardiology.