Clinical Heart and Vascular Center

Exercise Harm vs. Help: Is There a Goldilocks-Like Sweet Spot?

Benjamin Levine
Benjamin Levine, M.D.

By Benjamin Levine, M.D.
Director, Institute for Exercise and Environmental Medicine
Professor of Internal Medicine

Everyone wants to know how much exercise to do for optimal health. At the AHA this year, I participated in a cardio­vascular seminar titled “Controversies in Exercise Training”; my particular task was to address the questions of whether it is possible to do too much exercise and actually harm your heart, and is there a Goldilocks-like “sweet spot” that is just right?

I find there are four key issues that come up frequently when I discuss this subject with my patients. The first is survival. It seems clear from the study of thousands of athletes that being an athlete is associated with improved survival. Moreover, the updated physical activ­ity guidelines presented also at this year’s AHA meeting make it quite clear that evidence from hundreds of thousands of patients and healthy individuals shows that a) some exercise is better than none; and b) in general, more is better. Although the “dose” of exercise is a bit hard to quantify, it seems clear that three to five hours per week of physical activity ranging from mod­erate to vigorous exercise gets the vast majority of this effect, though there might be some small advantage in up to six to eight hours per week, especially for outcomes such as heart failure. More exercise than that, which is typically prac­ticed by competitive marathoners or triathletes, is of course necessary for competitive fitness but does not confer immortality or protection from cardiovascular disease.

Our own data from UT Southwestern demonstrate that exercising four to five days per week as part of a lifelong commitment to fitness and health can preserve the youthful structure of the heart and blood vessels and is a great target for public health.

Benjamin Levine, M.D.
Exercise prescription
Graphic courtesy of Alejandro Palacios, The University of Texas at Austin

Our own data from UT Southwestern demonstrate that exercising four to five days per week as part of a lifelong commitment to fitness and health can preserve the youthful structure of the heart and blood vessels and is a great target for public health. My own “Exercise Prescription for Life” is shown in the figure.

But it is possible to cause some harm dur­ing exercise. For example, patients who inherit genes that alter the nature of cardiac structural proteins might accelerate their disease, and for them, high-intensity or prolonged exercise should be avoided. Extraordinary endurance efforts can cause some swelling and possible scarring of the heart, though this is contro­versial. Very high doses of exercise training (in that eight hours or more per week range) is associated with calcium in the coronary arteries, though it is reassuring that these lesions are stable, rarely cause heart attacks, and are not associated with increased risk of death. Probably the least controversial “harm” of high doses of exercise (more than the three to five hours per week of the guidelines) is the increased risk of atrial fibrillation; this risk might be as much as fivefold higher in highly competitive Masters athletes, though lower doses are actually protec­tive. Overall though, the benefits of exercise far outweigh the risks and should be considered part of a healthy individual’s personal hygiene.