It is overwhelmingly established that exercise helps to prevent heart attacks (J Am Coll Cardiol, 2016;67:316–329), but a recent study showed that very vigorous exercise may be associated with increased plaque size (Circulation, Mar 28, 2023;147(13):993-1003).
For more than six years, researchers followed 289 men, ages 50 -60, who exercised for an average 41 MET hours per week (range of 25-57 hours). MET hours per per week is a measure of intensity of exercise compared to sitting completely still. The men were divided into three exercise groups: moderate intensity, controlled vigorous intensity and very vigorous intensity.
The study found that:
• The group who exercised at moderate intensity and those who did controlled vigorous exercise had minimal increases in plaque size
• The group of men that exercised most vigorously had the greatest increase in plaque size
• How much a person exercised (length of time) did not affect the progressive size of the plaques in any of the exercise groups.
How Plaques Form in Arteries
A heart attack is not caused by narrowed arteries, it is usually caused by a plaque breaking off, followed by bleeding. Then a clot forms to completely obstruct all flow of blood through that artery leading to the heart muscle. That part of the heart muscle lacks oxygen so it dies. Plaques are formed by inflammation, where an overactive immune system punches holes in the inner lining of arteries to cause the first step in the formation of an arterial plaque. Your immune system is controlled by the types of bacteria in your colon which are determined significantly by what you eat. Therefore, diet is felt to be a major contributor to the formation of plaques in arteries.
Exercise Stabilizes Plaques
Exercise is not a significant factor to determine the size of plaques, but it can stabilize plaques so they are less likely to break off (Circulation. 2020; 141:1338–1350). Doctors can measure plaque size, and increased plaque size is associated with increased heart attack risk (JACC Cardiovasc Imaging, 2012; 5:990–999). Older people who exercise vigorously have a very low rate of heart attacks, even though they have larger plaques than non-exercisers at the same age (Circulation, 2017; 136:126–137). Athletes may eat a lot of food to meet their increased energy needs. Certain foods such as meat, sugar-added and fried foods, encourage the growth of harmful colon bacteria that cause inflammation and increased plaque growth.
Exercising long and hard through significant muscle pain and shortness of breath can cause muscle damage. Prolonged vigorous exercise damages muscle fibers at their Z-lines (J Physiol, Dec 1, 2001;537(Pt 2):333–345). For younger people, that may not be a problem because muscle fiber damage turns on their immune system so that they produce large amounts of antioxidants, healing cells and cytokines and are at reduced risk for heart attacks (Physiol Res, 2020 Aug; 69(4): 565–598). In older men, the muscles will not heal as rapidly as those of younger men. The prolonged muscle damage turns on their immune system to cause increased inflammation and increased plaque formation in their arteries. Since eating meat, sugar-added foods and drinks and fried foods causes inflammation (Curr Dev Nutr, Jan, 2022;6(Suppl 1):994) and inflammation causes plaques to form (J Transl Int Med, Mar, 2022;10(1):36–47), a pro-inflammatory diet is a far stronger driver of plaque formation in arteries (Front Nutr, Jun 14, 2022; 9: 920892).
Extreme exercise through severe muscle pain can cause muscle damage, which can cause inflammation that can increase the size of arterial plaques (Circulation, 2023;147(13):993–1003). Exercise does not prevent plaques from forming in arteries, but exercise can stabilize plaques so they are less likely to break off to cause a heart attack (Circulation, 2020;141(16):1338–1350). Since exercise helps to prevent heart attacks and prolong lives, exercisers are less likely to suffer heart attacks (Mayo Clin Proc, 2014; 89:1195–1200).
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.