In an article in this month's Mayo Clinic Proccedings researchers looked at an emerging body of papers that point to the fact that even exercise can have diminishing returns.
The authors surveyed more than 50 different studies that followed athletes who chronically trained and participated in extreme endurance events, such as marathons, ultramarathons, Ironman triathlons, and long-distance bicycle races. The studies found that excessive training and competing can cause cardiovascular damage such as scarring and enlargement of the heart and blood vessels, as well as irregular heart beating.
The paper cited that veteran marathon runners and professional cyclists were five times more likely to have irregular heart beats.
While rare, there have been incidences where runners have actually collapsed from cardiac arrest during long road races.
But the authors were also adamant that these findings should not dissuade people from regular exercise. Lead author Dr. James O'Keefe, a cardiologist at the Mid America Heart Institute, said, "We want people to understand that this in no way detracts from the importance of exercise. Physically active people are much happier than their sedentary counterparts. So much so, that they live up to seven years longer."
According to the Centers for Disease Control and Prevention, adults should get at least 30 minutes of moderate exercise, like walking, five times a week, in addition to two days or more of muscle strengthening activity.
O'Keefe said that many people misunderstand exercise and think more is always better.
He points to his own patients - many are athletes who come in and say they are training for marathons, running several hours a day. O'Keefe tells them that it's not good orthopedically.
"It's definitely not good for your heart in the long run. If you want to do it, train up for it, and cross it off your bucket list. This is not a healthy, long-term exercise pattern."
Rather O'Keefe suggests people do a lot of brisk to moderate exercise like walking, jogging, and swimming.
"You can do light to moderate exercise as long as you want. We're genetically designed for that kind of activity. We're just not designed to run 26 miles at a time, or 100, or go on a full distance triathlon for 12 hours as hard as you can go."
™ & © 2012 Cable News Network, Inc., a Time Warner Company. All rights reserved.