How much exercise is enough?

Executive summary

* This week’s note looks at a population study of almost half a million US adults, followed for approximately 18 years, to assess how much and what type of exercise is associated with lower mortality.

* Current World Health Organization (WHO) recommendations are that we do 150 minutes or more each week of moderate-intensity aerobic physical activity or 75 minutes per week of vigorous-intensity aerobic physical activity or an equivalent combination of the two.

* As an epidemiological study, this suffered the usual flaws – honesty of self-reporting, association not causation, relative not absolute risk, and a healthy person confounder. Data that would normally help readers to assess these were absent from the paper.

* The two key findings were 1) total aerobic physical activity (whether moderate or vigorous) of 3 hours per week and 1-2 sessions of muscle strengthening exercise per week makes a significant difference to mortality. 2) There is minimal evidence that doing more than this reduces mortality risk further.

* There were many limitations with the study, but the two findings were interesting and may be encouraging to those who think they need to be doing more than this to benefit.


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