Is too much of exercise bad for you?

Is too much of exercise bad for you?

It is well known that regular exercise is good for the heart. Almost all guidelines recommend 150 minutes a week of moderate intensity physical activity. But like the old saying that too much of good things can be harmful, is too much exercise bad for you?

The Copenhagen City Heart Study assessed the dose of jogging and long term mortality [1]. In the introduction of their article, they mentioned the historical anecdote of sudden death of Pheidippides, a professional running courier in 490 BC. It is believed that he ran from Marathon to Athens, Greece, approximately 25 miles to give the news of victory of Athens overs Persia. He exclaimed “Nike'” (victory), collapsed and died. But they also quote another version of this story which says that Pheidippides continued to run from Athens to Sparta for military help. He is supposed to have run the distance from Athens to Sparta of 137 miles in 48 hours!

1098 healthy joggers and 3950 healthy non joggers have been prospectively followed as part of the Copenhagen City Heart Study since 2001 [1]. The study showed that 1 to 2.4 hours of jogging per week was associated with lowest mortality. They noted that the optimal frequency of jogging was 2 to 3 times per week and optimal pace was slow or average. When they divided joggers into light, moderate and strenuous, the lowest hazard ratio for mortality was found in light joggers followed by moderate joggers and strenuous joggers. These findings suggested a U-shaped association between all-cause mortality and dose of jogging by pace, quantity and frequency. Light and moderate joggers had lower mortality than sedentary non joggers. Mortality rate of strenuous joggers was not statistically different from that of the sedentary group.

Million Women Study was a prospective study started in 1998 with about 1.1 million women without prior vascular disease [2]. During an average follow up of 9 years, 49,113 women had a first coronary heart disease event, 17,822 had a first cerebrovascular event, and 14,550 had a first venous thromboembolic event. Compared to inactive women, those reporting moderate activity had significantly lower risk of all three events. But women reporting strenuous physical activity daily had higher risks of all the three events than those doing such activity 2 or 3 times per week.

One of the earliest studies to report a similar relationship between intensity of exercise and mortality was one on all-cause mortality and longevity of college alumni [3]. That study evaluated 16,936 Harvard alumni, aged 35 to 74. A total of 1413 alumni died during 12 to 16 years of follow up. Death rate was found to decline steadily as energy spent on activity increased from 500 to 3500 Kilocalories per week. But beyond that, it increased slightly, again indicating a so called U-curve or reverse J-curve. Rates were one quarter to one third lower among alumni spending 2000 or more Kilocalories during exercise per week than among less active men.

It should be noted that all these studies have uniformly documented the long term benefits of exercise. Regular exercise programs tailored to each individual’s physical capacity is highly essential for good health and mortality benefits. The question is only regarding extremely strenuous and prolonged exercise.

References

1. Schnohr P, O’Keefe JH, Marott JL, Lange P, Jensen GB. Dose of jogging and long-term mortality: the Copenhagen City Heart Study. J Am Coll Cardiol. 2015 Feb 10;65(5):411-9. doi: 10.1016/j.jacc.2014.11.023. PMID: 25660917.
2. Armstrong ME, Green J, Reeves GK, Beral V, Cairns BJ; Million Women Study Collaborators. Frequent physical activity may not reduce vascular disease risk as much as moderate activity: large prospective study of women in the United Kingdom. Circulation. 2015 Feb 24;131(8):721-9. doi: 10.1161/CIRCULATIONAHA.114.010296. Epub 2015 Feb 16. PMID: 25688148.
3. Paffenbarger RS Jr, Hyde RT, Wing AL, Hsieh CC. Physical activity, all-cause mortality, and longevity of college alumni. N Engl J Med. 1986 Mar 6;314(10):605-13. doi: 10.1056/NEJM198603063141003. PMID: 3945246.