MINNEAPOLIS - Plenty of people take up marathon running to stay in shape.
But a new study finds, in some cases, too much running could be bad for your health.
Alyssa Downing of Minneapolis was running around Lake Calhoun on Tuesday because she said, "I have a half marathon on the books in Chicago so I'm getting in a last couple of training runs."
But now experts say you may want to stop after just one or two marathons because a new study published in the journal Mayo Clinic Proceedings says running long distances regularly may not only not help your health, it may harm it.
Cardiologist Dr. Retu Saxena of North Memorial Hospital in Robbinsdale agrees. She said, "What we find is that people who are extreme marathoners have little tiny areas of small heart attacks so to speak."
The study out of the Mid America Heart Institute of St. Luke's Hospital in Kansas City, Mo., said those who participate in frequent marathons or triathlons, even long distance bike races, put too much stress on their hearts.
Saxena said that stress makes muscle fibers tear, weakening the heart. "What you see on the MRI's is you actually see the muscle being replaced with what we call patching necrosis or scar tissue," Saxena said. She said the heart muscle also stiffens and the damage can lead to atrial fibrillation.
The study authors said the overall longevity of extreme runners is no different than the population as a whole, but it's not better either.
For those who have never wanted to run a marathon, this may relieve a little of the guilt for not having that goal. However it's not a pass to just kick up your feet and do nothing.
Saxena said moderate exercise daily is important for everyone. "What we have found is 30 to 60 minutes of moderate exercise adds seven years on to your life expectancy and that's where we should be aiming," Saxena said.
When asked what the best exercise for the heart is, Saxena said, "I think walking is the natural exercise that we were developed to do and that people should walk get your heart rate up, a nice brisk walk."
How about running? The study authors said the optimal dose of running is 10 to 15 miles a week.
Nick Menth of St. Cloud, who was also running around Lake Calhoun, said he runs more than that in a week but, "I'm not putting in extreme miles right now so I'm going to keep doing what I'm doing."
Saxena says any exercise in moderation, biking, hiking, rollerblading, that gets your heart rate up for 30 minutes, will send you in the right direction.
(Copyright 2012 by KARE. All Rights Reserved.)