Extreme Exercise May Be Bad for the Heart

Doctors generally advise their patients to exercise more. The more people exercise, the better their health and longevity. But according to a recent study published in the journal Mayo Clinical Proceedings, there is such a thing as too much exercise. At some point, the health benefits of exercise start to wane, and serious health consequences make themselves known. 

Dr. James O’Keefe, a cardiologist at the Mid America Heart Institute of St. Luke’s Hospital in Kansas City, Missouri, led the study and found that extreme exercise isn’t good for the heart. He focused his attention on people who participated in marathons, triathlons, ultramarathons, or long bike races. These are the same individuals who would generally be classified as fit, but O’Keefe’s research reveals otherwise. According to the studies he had reviewed, runners show a 50-percent increase in the enzyme troponin during and after a marathon. Troponin is apparently a sign of heart damage and is produced when the heart is distressed.

According to O’Keefe, the heart pumps about five quarters of blood per minute when at rest. More intense physical activity, however, pushes the rate to about 30 to 40 quarts of blood per minute.  "If you go and run for 26 miles or do a full-distance triathalon, it completely overtaxes the heart. The heart is pumping 25 quarts a minute for hours and hours, and that starts to cause muscle fibers to tear, which leads to a bump in troponin and other enzymes associated with inflammation, and it causes the death of some muscle cells in the heart."

The study isn’t meant to scare anybody off from exercising; it’s just meant to remind everyone not to overdo it and to practice caution. New data, presented at the annual meeting of the American College of Sports Medicine, by one of the study co-authors, Dr. Carl Lavie, shows that the optimal dose of running seems to be at 10 to 15 miles (around 16 to 24 kilometers) per week—any more than that, and people risk tearing their muscle fibers. The damage doesn’t happen overnight, either, and can take years to really cause damage. 

For safe exercising, researchers suggest working out for 15 minutes to an hour each day for several days a week. Following that routine is enough to get you your health benefits as well as keep you from overtaxing yourself.

(Photo by Ed Yourdon via Flickr Creative Commons; used for illustrative purposes only)