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Fourteen runners who took part in the Winnipeg marathon put their hearts into it, subjecting themselves to blood tests, echocardiograms and an MRI to learn more about how their tickers function following a race.

And the good news is that although there was short-term cardiac injury after running, there was no permanent heart muscle damage.

The findings by researchers at St. Boniface General Hospital and the University of Manitoba were published this past week in the American Journal of Cardiology and announced at a news conference Friday in Winnipeg.

The amateur athletes ranged in age from 18 to 40 and took part in last year's 42-kilometre Manitoba Marathon.

They had baseline blood work and baseline ultrasounds before they ran and underwent the tests again soon after crossing the finish line, principal investigator Davinder Jassal said from Winnipeg.

Dr. Jassal said he had been involved with similar research a few years ago while at Harvard University's medical school and the work was done on participants who ran the Boston Marathon.

But the new wrinkle he incorporated into the Winnipeg experiment was the MRI, or magnetic resonance imaging, which provides what he calls "exquisite detail."

"And the MRIs of the heart confirm that, yup, the right side of the heart doesn't pump and function efficiently [after the race]" he said.

"The good news is that it does recover at Week 1 - so when the marathoners recover and we study them 'Week 1' later, after [a]marathon, their right ventricle comes back to normal and it pumps effectively."

The blood work indicated that myoglobin, creatine kinase and troponin T - biomarkers used to identify cardiac stress, such as heart attacks - were elevated in the athletes after the race.

"Importantly, the MRI shows that although these chemicals are released in the body, which may suggest that there may be some heart damage, when you look on the MRI there's actually no permanent heart damage whatsoever," Dr. Jassal said.

"So running a marathon if you're trained for it is a safe thing."

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

And he noted that one week after the race, the diastolic properties of the heart, which is its ability to receive blood, still stayed a little abnormal.

"We don't know what's going to happen when that ability of the heart to relax actually improves at Week 2, Week 4," he said. "No one knows the answer to that."

Dr. Jassal plans to do similar research at this year's Manitoba Marathon, on runners doing the half-marathon. Some of the runners among them will be novices, he said.

"I'm curious to see what actually happens to their heart in the sense of does it actually recover at one week after the race."

He wants to do another study in 2010 in Winnipeg looking at the hearts of runners who have completed several marathons in previous months.

Of the 14 athletes in this study, 10 were moderately trained - defined as running less than 64 kilometres a week before the race - and the other four were considered highly trained, racking up more than 64 kilometres a week.