Overdosing on exercise? Study says extreme endurance training can damage your heart


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Get this: People who regularly partake in extreme endurance training may be causing structural changes to their heart and large arteries, leading to injury of the heart, according to a study in the June issue of Mayo Clinic Proceedings.

Although most endurance trainers are in it for more than the workout — they’re also in it for the spiritual quest between mind and body — these findings should be considered before embarking on a 100-mile fun run. For us other fitness folk who feel that if our muscles aren’t on fire and the sweat is not dripping, the workout was a waste of time, this comes as a relief. We don’t need to go to extreme measures to stay healthy. That 20-minute walk is more helpful than we think.

According to the study, which can be found here, chronic training for and competing in extreme endurance events — such as marathons, ultramarathons, ironman distance triathlons and very long-distance bicycle races — can be bad for your heart. It can cause transient acute volume overload of the atria and right ventricle, with transient reductions in right ventricular ejection fraction and elevations of cardiac biomarkers (i.e., substances that are released into the blood when the heart is damaged or stressed), all of which return to normal within one week.

Over months to years of repetitive injury, this process, in some individuals, may lead to patchy myocardial fibrosis (i.e., abnormal formation of fibrous tissue in the heart), creating a substrate for abnormal rapid heart rhythms in the atria and lower chambers of the heart.

Long-term excessive sustained exercise may be associated with coronary artery calcification, diastolic dysfunction (i.e., an abnormal stiffening of the ventricles) and large-artery wall stiffening. The study points out that this concept is still hypothetical and there is some inconsistency in the reported findings.

“What we’re concerned about is the people doing extreme endurance exercise — ultra-marathons, marathons, 200-mile bike rides, the Tour de France,” said lead author James H. O’Keefe of Saint Luke’s Hospital of Kansas City, Mo., in a video about the study. “Granted these are a small minority of people, but what we’re trying to clear up is that this is not really conducive to great long-term cardiovascular health. You’re better off backing off and doing an hour of intense aerobic exercise, and you probably don’t have to average more than 30 to 60 minutes. Beyond that, it’s a point of diminishing returns.”

This doesn’t mean all exercise is bad! O’Keefe stressed that physically active people are much healthier than their sedentary counterparts — so much so that on average they live seven years longer than someone who doesn’t exercise at all.

Less intensity is better
“What this paper points out is that a lot of people misunderstand that if moderate exercise is good, than the more is better, when in fact most of the lion’s share of benefits of exercise accrue at relatively modest levels,” O’Keefe explained. “In other words, getting out for a 20 to 30 minute walk per day is a really great exercise. Data indicates that running distances in the ranges 2 or 3 or 4 miles is plenty. Other days you [should] do things like cross-training, strength training, yoga, walking [or] swimming.”

O’Keefe says many people fall off their exercise routine because they feel like if they don’t go to the gym for an hour and a half, or don’t go out for a long run, it’s not doing them any good.

“In fact the opposite is true,” he said. “Getting out for a 20-minute walk with your dog, taking the stairs or jogging rather than hardcore running are healthy exercise patterns that do bestow a lot of cardiovascular benefits. It’s counterproductive to be doing extreme endurance athletic events — not to say that you can’t do a few; just don’t make a career out of it. It’s not good for your heart and not good for your blood vessels.”

This study follows the news of 58 year-old legendary ultra-marathoner Micah True, who died in March during a routine 12-mile run. True was the inspiration for the character Caballo Blanco in the endurance-running bestseller “Born to Run.” His autopsy results, which were released last month, showed that his heart was enlarged and scarred and that he died of a lethal arrhythmia (irregularity of the heart rhythm).