Minimum Effective Dose of Exercise

The smallest amount of physical activity at which measurable health benefit appears. The evidence paged so far converges on one shape: the dose-response curve is steeply front-loaded — the largest reduction in mortality risk comes from going from nothing to a little, and each further increment buys less.

The curve, in numbers

Dose	Population / method	Finding	Source
Below WHO minimum (< 150 min/week moderate)	~660,000 US adults, self-report, 14-yr follow-up (2015 meta-analysis)	20% lower mortality vs none; 31% at 1–2× guideline; 37% at 2–3×	How Little Exercise Can You Get Away With (Economist)
Median 4.4 min/day of vigorous bursts (VILPA)	~25,000 UK non-exercisers, accelerometer, ~7 yr	up to 30% lower all-cause mortality	same
~7,000 steps/day vs 2,000	31 studies / 24 cohorts, device-measured (2025 meta-analysis)	HR 0.53 for mortality; inflection at 5,000–7,000	Do You Need to Walk 10,000 Steps a Day (Economist)
15–30 min/day extra activity	~482,000 Taiwanese adults with sedentary jobs	erases most of the excess mortality of workplace sitting	Why Standing at Your Desk May Be Little Better Than Sitting (Economist)

Two different currencies — minutes of moderate/vigorous activity and daily steps — both saturate well below the popular targets (150 min/week; 10,000 steps).

Intensity vs volume

The VILPA data suggest intensity in short bursts may matter disproportionately: a few minutes a day of running for a bus or climbing stairs carried an association comparable to much larger volumes of moderate activity. The mechanism is unexplained (the HIIT analogy is a hypothesis). "Exercise snacks" are the practical gloss academics have put on it. VR boxing games measured at 8–9 METs (Exergaming) are one way a non-exerciser reaches that vigorous band.

What the evidence does not establish

• Every row above is observational. Reverse causation (the healthy move more) is addressed statistically, never eliminated.
• The 2015 pooled data are self-reported. The wearable studies fix measurement but not confounding.
• Nothing here speaks to strength training, the second half of the WHO guideline; the curve is for aerobic/incidental activity and mortality only.
• Whether the floor is the same at all ages is unknown (the steps meta-analysis had no age-specific analysis).

Related

• Step Count Targets — the steps-denominated version of the same question.
• Sedentary Behaviour — the floor also appears to offset the harm of sitting, which is why "still vs moving" is the operative distinction.
• Running Injury — the other end of the curve: where more running starts to cost.
• Heat Acclimatisation — a different minimum: 4–7 days of exposure for 75–80% of adaptation.