Exercise prescription

The United States Department of Health and Human Services just came out with the second edition of its physical activity guidelines for Americans. (1) It’s a 118 page book but it has lots of pictures and it is summarized in this issue of The Journal of the American Medical Association (JAMA), (2) and then further commented on (3) and hereby commented on by me now. Then there is also this, in the same issue of JAMA – “Joint Prevalence of Sitting Time and Leisure-Time Physical Activity Among US Adults, 2015-2016.” (4)

According to the book the health benefits of regular physical activity include “- Slowed or reduced weight gain. – Weight loss, particularly when combined with reduced calorie intake. and – Prevention of weight regain following initial weight loss.” In children the health benefits include “Improved weight status.”

Ah, no. I don’t think so. But aside from these few bones of contention it is impossible not to conclude that exercise is a cure all.

It is important to realize that there are really very few highest standard studies of the benefits of exercise in humans because such studies are difficult to impossible to do, especially when the outcome is longevity. So most of this stuff is based on the notoriously flawed observational standard.

The prescription sounds suspiciously exact – “adults should do at least 150 minutes (2 hours and 30 minutes) to 300 minutes (5 hours) a week of moderate-intensity, or 75 minutes (1 hour and 15 minutes) to 150 minutes (2 hours and 30 minutes) a week of vigorous-intensity aerobic physical activity.”

Moderate intensity is like brisk walking and vigorous intensity is like jogging or running. Children and old people also get specific prescriptions. Furthermore, “adults should also do muscle-strengthening activities of moderate or greater intensity and that involve all major muscle groups on 2 or more days a week, as these activities provide additional health benefits.” This is for the precisely defined result of “substantial health benefits.”

Probably the biggest relative benefits would accrue to people who go from zero to just a little move it-move it and everybody, no matter what may afflict them, can benefit. There are no contraindications to exercise of some kind. Doctors should never prescribe rest for anything.

This is an “at least” prescription. More exercise is even better. Who knows how much benefit would come from running a marathon twice a day or where the benefits of more exercise start to plateau and decline.

Today 80% of us are not following this prescription. If we only would, the decrease in morbidity and mortality would be big. For example “a 26% relative reduction in cardiovascular mortality” is mentioned.

Not even Trump will argue with doing more exercise. Just do it like the Nike commercial says.

1. US Department of Health and Human Services. Physical Activity Guidelines for Americans. 2nd ed. Wasington, DC: US Dept of Health and Human Services; 2018.

2. Piercy KL, Troiano RP, Ballard RM, et al. The Physical Activity Guidelines for Americans [published online November 12, 2018]. JAMA. doi:10.1001/jama.2018.

3. Thompson PD, Eijsvogels TMH. Physical Activity Guidelines. A Call to Activity for Clinicians and Patients. JAMA. 2018;320(19):1983-1984. doi:10.1001/jama.2018.

4. Ussery EN et al. Joint Prevalence of Sitting Time and Leisure-Time Physical Activity Among US Adults, 2015-2016. JAMA. 2018;320(19):2036-2038. doi:10.1001/jama.2018.