Aerobic exercise is the best-evidenced lifestyle intervention in medicine, and the question is no longer whether it is associated with living longer but how the dose-response curve is shaped. Two kinds of evidence answer that: questionnaire cohorts, which are enormous, and accelerometer cohorts, which are smaller but measure movement rather than memory of it.

Both agree on the shape. The steepest part of the curve is at the bottom. Moving an inactive person to a moderate amount of activity is associated with a large reduction in risk; moving an active person to a very active one is associated with a small further reduction, and beyond a point the data run out.

Regular aerobic exercise improves cardiorespiratory fitness, which is itself one of the strongest predictors of survival. It lowers blood pressure and resting heart rate, improves insulin sensitivity and lipid profiles, reduces visceral fat and systemic inflammation, and improves endothelial function. Each is a measured effect in trials, and each is a route to less cardiovascular disease, less diabetes and less of several cancers.

The accelerometer studies add that light activity, the kind that does not count as exercise, is also associated with lower mortality, and that sedentary time is associated with higher mortality in a dose-dependent way that high physical activity can offset.

The questionnaire cohorts. A 2023 dose-response meta-analysis in the British Journal of Sports Medicine pooled 196 articles from 94 cohorts with over 30 million participants. Risk fell steeply up to 8.75 marginal MET-hours a week, equivalent to the recommended 150 minutes of moderate-to-vigorous activity, where all-cause mortality was 31% lower and cardiovascular mortality 29% lower than in the inactive. Above that, differences were smaller to 17.5 MET-hours and small and uncertain beyond. If every inactive adult reached that level, the authors estimated 15.7% of premature deaths would be averted.

The accelerometer cohorts. A 2019 harmonized meta-analysis of eight studies with 36,383 participants, all with device-measured activity, found hazard ratios for mortality of 0.48, 0.34 and 0.27 across the second, third and most active quarters compared with the least. Light activity counted, and sedentary time was associated with up to 2.6 times higher mortality in the most sedentary quarter.

Sitting and exercise. A 2016 harmonized analysis of over a million people found that daily sitting time was not associated with higher mortality in the most active quartile, while in the least active, sitting more than eight hours a day carried 59% higher mortality. High activity offset sitting; low activity did not.

Running specifically. A 2020 meta-analysis of 14 studies in 232,149 people found running associated with 27% lower all-cause, 30% lower cardiovascular and 23% lower cancer mortality, with no dose-response for frequency, duration, pace or volume: any running, even once a week, was associated with the benefit, and more was not clearly better.

The risks are musculoskeletal injury, which scales with sudden increases in volume, and rare cardiac events during vigorous exertion, concentrated in people with existing heart disease. Both are reasons to progress gradually and, for older or symptomatic people, to be assessed first. There is no evidence of harm from the amounts of activity in the guidelines, and the flattening at the top of the curve is a lack of further benefit rather than a cost.

Not a product. The World Health Organization and national guidelines recommend 150 to 300 minutes of moderate or 75 to 150 minutes of vigorous aerobic activity a week for adults, with the explicit note that some is better than none. This site links to those guidelines.