Study: Strenuous Exercise As Bad As No Exercise

A new study finds that light jogging may contribute to a longer life, but strenuous jogging may still be better than not jogging at all.

In an effort to investigate the association between jogging and long-term, all-cause mortality, a team including investigators from the Mid-America Heart Institute and the University of Frederiksberg Hospital in Copenhagen, Denmark focused on the effects of pace, quantity, and frequency of jogging.

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As part of the Copenhagen City Heart Study, 1,098 healthy joggers and 3,950 healthy non-joggers were prospectively followed since 2001, with the researchers performing a Cox proportional hazards regression analysis with age as the underlying time scale and delayed entry. The optimal frequency of jogging was 2 to 3 times per week or 1 time per week, and the optimal pace was slow or average. Joggers were classified as either light, moderate, or strenuous joggers. The lowest hazard ratio for mortality was found in light joggers, followed by moderate joggers.

While exercise is “one of the best ways of improving long-term cardiovascular health and overall life expectancy,” the findings suggest a “U-shaped” relationship between exercise and risk of early death, says James O’Keefe, MD, a cardiologist at Mid-America Heart Institute, and a co-author of the study.

“The benefits are maximized with light to moderate exercise over the decades,” says O’Keefe. “Very high levels of strenuous exercise, like running marathons or doing full distance triathlons, are not only unnecessary, but will likely erode some of the benefits that one would get with less extreme doses of exercise. So I encourage my patients to exercise but tell them to limit their strenuous [jogging] to no more than 5 hours per week.”

Light jogging “confers a longevity benefit of about 6 years in comparison to no exercise at all,” adds Gorm B. Jensen, MD, DMSc, a professor at Frederiksberg Hospital, and a study co-author.

“The benefit is lost in persons who participate in strenuous jogging,” he continues. “The advice to patients in primary care should therefore be [that] even very light exercise is better than no exercise at all, moderate exercise is best, while strenuous exercise is no better than no exercise at all. In fact, very strenuous exercise—an Ironman [triathlon], for instance—may be harmful.”

—Mark McGraw


Schnohr P, O’Keefe J, et al. Dose of Jogging and Long-Term Mortality: The Copenhagen City Heart Study. J Am Coll Cardiol. 2015.