Notes
This book gives general information. It isn't medical advice, and it's no substitute for a doctor or physiotherapist who knows your situation. The NHS advises speaking to a GP before starting if you haven't exercised for some time or have medical conditions or concerns.
I've kept sources out of the chapters where I could so they read easily. Here they are by chapter, with the limits I'm aware of. Unless I say otherwise, I read the published summary of each paper and not the full text. I checked each paper for a retraction notice in September 2026 and found none. Where a chapter isn't listed, it rests on my own reasoning. That includes chapters 1, 2, 6, 7, 10 and 15, and the rule in chapter 13. The NHS pages were read in September 2026. They're written for England or the UK. Nearly all the studies of activity and mortality are observational. They show that people who move more die later, and they can't prove that the movement is the cause. People who are already unwell move less, which inflates the apparent benefit.
Before you start. The advice is from the NHS pages "Physical activity guidelines for adults aged 19 to 64", "Chest pain" and "Overview, eating disorders".
Chapter 3. Arem and twelve colleagues, "Leisure time physical activity and mortality: a detailed pooled analysis of the dose-response relationship", JAMA Internal Medicine 175, 2015, pages 959 to 967. The hazard ratios were 0.80 for some activity below the recommended minimum, 0.69 at one to two times the minimum and 0.61 at three to five times. Activity was self-reported. Wen and nine colleagues, "Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study", Lancet 378, 2011, pages 1244 to 1253. Activity was self-reported. Ekelund and nineteen colleagues, "Dose-response associations between accelerometry measured physical activity and sedentary time and all cause mortality: systematic review and harmonised meta-analysis", BMJ 366, 2019, l4570. The hazard ratios for total activity were 0.48, 0.34 and 0.27 for the second, third and fourth quarters against the least active quarter.
Chapter 4. Jakicic and eight colleagues, "Association between bout duration of physical activity and health: systematic review", Medicine and Science in Sports and Exercise 51, 2019, pages 1213 to 1219. Saint-Maurice, Troiano, Matthews and Kraus, "Moderate-to-vigorous physical activity and all-cause mortality: do bouts matter?", Journal of the American Heart Association 7, 2018, e007678. The journal later published a correction to this paper, which I haven't read. Bull and twenty-nine colleagues, "World Health Organization 2020 guidelines on physical activity and sedentary behaviour", British Journal of Sports Medicine 54, 2020, pages 1451 to 1462. My account of where the ten-minute rule came from, and my statement that American and WHO guidance no longer include it, are from my general understanding and I haven't checked the guideline documents themselves. Stamatakis and six colleagues, "Association of wearable device-measured vigorous intermittent lifestyle physical activity with mortality", Nature Medicine 28, 2022, pages 2521 to 2529. There were 852 deaths among 25,241 people. Jenkins, Nairn, Skelly, Little and Gibala, "Do stair climbing exercise 'snacks' improve cardiorespiratory fitness?", Applied Physiology, Nutrition, and Metabolism 44, 2019, pages 681 to 684. The summary gives 60 steps per climb. That each climb took under a minute is my estimate.
Chapter 5. Hansen, Stevens and Coast, "Exercise duration and mood state: how much is enough to feel better?", Health Psychology 20, 2001, pages 267 to 275. The summary doesn't give the number of participants. Ruby, Dunn, Perrino, Gillis and Viel, "The invisible benefits of exercise", Health Psychology 30, 2011, pages 67 to 74.
Chapter 8. The dieting research is Herman and Mack, "Restrained and unrestrained eating", Journal of Personality 43, 1975, pages 647 to 660, and later work by Polivy and Herman. Applying it to exercise is my parallel. Lally, van Jaarsveld, Potts and Wardle, "How are habits formed: modelling habit formation in the real world", European Journal of Social Psychology 40, 2010, pages 998 to 1009. The behaviours I mention are illustrations of the kind of thing participants chose. Of 96 volunteers, 82 gave enough data, and the model fitted well for 39.
Chapter 9. Ekkekakis, Parfitt and Petruzzello, "The pleasure and displeasure people feel when they exercise at different intensities", Sports Medicine 41, 2011, pages 641 to 671. Kaushal and Rhodes, "Exercise habit formation in new gym members: a longitudinal study", Journal of Behavioral Medicine 38, 2015, pages 652 to 663. That harder past sessions make future ones easier to cancel is my inference.
Chapter 11. Lee, Shiroma, Kamada, Bassett, Matthews and Buring, "Association of step volume and intensity with all-cause mortality in older women", JAMA Internal Medicine 179, 2019, pages 1105 to 1112. Median steps in the four groups were 2,718, 4,363, 5,905 and 8,442. The hazard ratio for the second group against the first was 0.59. My conversion of 1,700 steps to about fifteen minutes of walking is a rough estimate.
Chapter 12. All of the guidance is from the NHS page "Physical activity guidelines for adults aged 19 to 64". The example routine is mine and hasn't been tested. I didn't review research on short strength sessions.
Chapter 13. Plans in "when, then" form are from Gollwitzer and Sheeran, "Implementation intentions and goal achievement: a meta-analysis of effects and processes", Advances in Experimental Social Psychology 38, 2006, pages 69 to 119. The rule and its five parts haven't been tested together, and what I say to expect is my expectation and not a finding.
Chapter 14. Couch to 5K is mentioned on the NHS guidelines page as a nine-week running plan for beginners.