Countless studies have shown that exercise helps to prevent heart attacks, but some researchers have found scarring in heart muscle and increased plaques in the heart arteries of men who have run many marathons and triathlons, resulting in news headlines warning of "too much exercise."
A study of 50 men who ran 3,510 marathons showed that some of these men had excess plaques in their heart arteries (Med Sci Sports Exerc, Dec 2017;49(12):2369-2373). The increase in plaques was proportional to the individual's conventional heart attack risk factors (previous smoking, high blood pressure, high cholesterol, a pro-inflammatory diet, etc.,) and appeared to be totally unrelated to the distances or number of years they ran. Indeed, those who had started running later in life had more plaques.
A study of endurance athletes who exercised more than 2000 METs/week showed more plaques in their arteries than those who exercised less. However, the endurance athletes had primarily stable plaques, not the mixed plaques that are the type that is more likely to break off to cause heart attacks (Circulation, April 27, 2017;136:138-148).
Master athletes who compete in endurance events in later life have far fewer plaques, and the plaques that they have are far more stable than the plaques of non-exercisers (Circulation, May 2, 2017).
A study of 12 life-long endurance athletes over 50 years of age found that six had evidence of scarring in their heart muscles that was associated with the number of years spent training and the number of competitive marathons (J Appl Physiol, Jun 2011;110(6):1622-6). None of these men had any heart problems or difficulty with running very long distances. Nobody knows the significance of this finding and nobody has shown that this scarring is associated with any heart problems in endurance athletes.
At this time, the prevailing opinion is that:
heart attacks are the result of sudden complete obstruction of blood flow to the heart caused by clots formed by plaques breaking off from arteries leading to the heart,
plaques form in arteries primarily from a faulty diet, and
exercise helps to prevent heart attacks by stabilizing plaques so that they do not break off to start the process that causes heart attacks.
Everyone should exercise unless they have a specific reason why they should not exercise. In addition to trying to exercise every day to stabilize the plaques in your arteries, you should follow a lifestyle that prevents plaques from forming in your arteries in the first place by:
eating lots of vegetables, fruits, nuts, beans, whole grains and other seeds
restricting all sugared drinks, including fruit juices, sugar-added foods, red meat, processed meats and fried foods
avoiding smoke, alcohol and recreational drugs
avoiding being overweight
keeping blood levels of hydroxy vitamin D above 20 ng/ml
Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe's full bio.