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Are you sure your heart can handle the strenuous long distance run that is necessary for marathons? Proper preparation for these runs proves to be vital for less fit athletes according to a new study.

Researchers evaluated 20 recreational long distance runners between the ages of 18 and 60 in order to investigate how their hearts responded to the dress. The runners took part in the Quebec City Marathon and had no known cardiovascular disease. In addition researchers prevented any runner who ran a marathon less than two months before the recruitment to participate in this analysis.

The subjects were tested six to eight weeks before the marathon and on the day of. Tests continued after 48 hours from the marathon completion which included a second MRI study and blood sample. 

"This timeframe guaranteed adequate rehydration (assessed according to hemoglobin level) and a return to baseline hemodynamic state (assessed according to heart rate and blood pressure) after the race, but was short enough to observe any significant myocardial changes before recovery," according to the study. "All runners with decreased left ventricular ejection fraction (LVEF), a measure of cardiac pumping efficiency, after the race compared with baseline underwent a third MRI study after three months of rest to check whether it had reversed.

Researchers found that, "the race induced a decrease in left and right ventricular function in half of the amateur distance runners. When a lot of the heart was affected, the heart also showed swelling and reduced blood flow." 

In this study, researchers observed that no permanent injury was for seen. It merely suggests that there may be a certain level of fitness needed to tolerate the strenuous heart activity before any long distance run. 

"We first established that marathon related segmental function decrease - observed in more than half of all segments - is associated with a decrease in resting perfusion and increase in myocardial edema," said senior author Eric Larose, DVM, MD, FRCPC, FAHA, of the Institut universitaire de cardiologie et de pneumologie de Québec (IUCPQ), Canada in a news release.

"Myocardial edema" is an abnormal accumulation of fluid in intercellular spaces of the body, according to the Medical Dictionary. 

The researchers said their objective is not to alarm less fit runners about the temporary changes in heart activity but instead to bring awareness that impermanent injury could be plausible. 

"These results emphasize the need for proper preparation before recreational distance runners engage in a marathon race," said Larose.The findings are published in the Canadian Journal of Cardiology.