New Study Asks: What is the optimal amount of daily activity vs exercise?

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Fastfitnesstips

5 min readAug 18, 2022

This is an old story, but one with confusing data. The U.S. Department of Health and Human Services’ current physical activity guidelines recommend as little as 150 minutes of moderate physical activity [MPA aka simple “activity”] per week (to which it has recently added 75 minutes of vigorous physical activity [VPA aka exercise]“or an equivalent combination of both.” Given that almost anything counts as MPA ie “activity” eg going for a walk, doing housework…..150mins is not very much. VPA ie “exercise” includes jogging, cycling, swimming etc.

This is also an area with a large number of beliefs, which might well be myths; or at least uncertainties and these are:

Guideline rates of exercise are enough
Too much activity (MPA) is bad for you, so only do a little
Too much exercise (VPA) is definitely bad for you, so only do a little
If you do MPA, then you don’t need any VPA

Fortunately a new study published in Circulation has examined all these, and the results are not as expected.

This study combined 2 large prospective US cohorts (Nurses’ Health Study and Health Professionals Follow-up Study, 1988–2018) in order to examine 116,221 adults using a self-reported questionnaire repeated up to 15 times beginning in 1986 and continuing for 30 years of follow up!

Myth 1: Guideline rates of exercise are enough

OK, Let us examine myth 1, that doing the recommended amount is enough.

During 2,984,545 person-years of follow-up (median, 26 years) there were 47,596 deaths. Thats a lot of data!

In terms of long-term leisure-time MPA, compared with those with no MPA, participants who met guidelines had 20% lower all-cause mortality and 22% lower CVD mortality

Compared with those with no VPA, participants who met the long-term VPA guidelines (75–149 min/wk of VPA) had 19% lower all-cause mortality and 31% lower CVD mortality

So far, so good, but if you did the optimal amount of MPA (500mins) you could lower your risk to 0.69 (ie 31% lower vs 20% above); and if you did the optimal amount of VPA ( 400mins) you could lower your risk to 0.73 (ie 27% lower vs 19% above)

Myth 2: Too much “easy” activity is bad for you, so only do a little

The research also showed a dose-response relationship, the more MPA you did, the better. This is shown on the the following graph, at 600 mins MPA (thats 10hr per week or 1.4hrs / day) you get 32% risk reduction

Now a thought experiment……given the line becomes almost linear after 500mins, what amount of time “active” would give 50% risk reduction?? If we model it, we can find out.

Risk of Mortality vs Active time Per Day

32% risk reduction = 1.4 hrs per day
50% risk reduction = 2.6 hrs per day
75% risk reduction = 4.7hrs per day
99% risk reduction = 6.6 hrs per day! (ok this one is likely broken!!)

Myth 3: Too much exercise (VPA) is definitely bad for you, so only do a little

This is interesting. The research also showed a dose-response relationship in terms of VPA / exercise, the more VPA you did, but there was a suggestion of a plateau, with not much benefit above 400mins VPA/week *but no evidence of harm either*

So, if you had a choice, you should not limit your VPA for fears of “no benefit”.

Myth 4: If you do MPA, then you don’t need any VPA

The researchers also looked at the *combination* of activity vs exercise . Here are the results. Each block at the bottom is a band of activity (MPA) and each coloured dot is a band of exercise (VPA)

What this shows is; if you are inactive, you get a massive benefit of any duration of exercise especially 150mins/week or more (thats 21mins per day)

However if you were doing roughly an hour a day or “activity” then the benefits of exercise were not as clear BUT this was confounded by large uncertainty in those doing no VPA (likely due to sample size).

Comparing Walking to Running

Many studies have shown that higher-intensity exercise yields more favorable effects on mortality and disease risk than lower-intensity exercise (ref). Running beats walking by a factor of 2:1 to 4:1, in terms of mortality reduction at isovolume. A 5-min run is as good as 15-min walk, and a 25-min run is as good as 105 mins walking.

Conclusion: Are US Guidelines Correct?

What this study shows is that if you do the minimum qualifying activity and exercise US guidance 150 minutes “activity” per week and 75 minutes of exercise you get about 30% risk reduction. BUT what we find is that by adding more MPA or more VPA you could get 40% or even 45% risk reduction.

Check out this second study from Zhao (Zhao M, et al. Br J Sports Med 2019;53:1405–1411). They found a 24% reduction in mortality from 600mins of easy activity but 42% reduction in mortality from 600mins of vigorous activity.