Ultra-marathons may cause heart damage, study says

Researchers have found that extreme endurance exercise can permanently change the heart–and not for the better. The review of studies, published in the new Mayo Clinic Proceedings, found that extreme exercise can lead to scarring of the heart and enlarged ventricles, Scientific American reported.

"What this paper points out is that a lot of people do not understand that the lion's share of health benefits accrue at a relatively modest level," the study's lead author, Dr. James H. O'Keefe of Saint Luke's Hospital of Kansas City, told Medical Daily. "Extreme exercise is not really conducive to great cardiovascular health."

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O'Keefe told the Kansas City Star that marathons are safe to try once, but not a good model for how you should regularly exercise. The potential dangers of extreme exercise were highlighted in March by the sudden death of 58-year-old ultra-marathon runner Micah True.  

An ultra-marathon is defined as any run that is longer than the standard marathon amount of 26 miles, according to Ultra Running Resource. The longest certified ultra-marathon in the world is The Ultimate Ultra, a 1300 mile race.

This research comes a month after a Copenhagen City Heart Study which found that jogging might deliver the best results. According to the study, people who jog as little as one hour per week at a "slow or average" pace actually had the best life expectancies.