Why too much exercise is bad for the heart

Masterfile

Moderation in all things is good advice, especially when it comes to exercise — or so suggests a recent study (via Time.com) on the negative effects extreme exercising may have on the body, in particular its consequences for the heart.  

U.S. cardiologist Dr. James O’Keefe reviewed studies on people who trained and participated in extreme fitness challenges such as marathons, triathlons, ultramarathons and various other endurance trials. What he discovered: when people put their bodies to the extreme test often enough they undermine the positive health benefits that come with consistent physical activity. In a sense, too much exercise makes people weaker.    

The Time.com article cites some of the detrimental effects of running and training for marathons. For example, the effort it takes to run a marathon taxes the heart muscle — the heart is forced to pump more blood for a longer period of time, creating a sustained condition of distress. Done frequently enough this distress increases the risk of tearing the heart’s muscle fibres.  

Said O’Keefe, “When you’re sitting around, your heart is pumping about five quarts of blood a minute, and if you run up the stairs or push yourself physically, it can go up 35 or 40 quarts a minute. If you go and run for 26 miles, or do a full-distance triathlon, it completely overtaxes the heart. The heart is pumping 25 quarts a minute for hours and hours, and that starts to cause muscle fibres 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.”

Over years and years of training, this damage to the heart muscle can increase the risk of abnormal heart rhythms, which could result in a cardiac event. 

Running is still good for the heart, but the study suggests people select a more heart-friendly approach to pounding the pavement. That magic number, according to the experts hovers around 10 to 15 miles a week.