Notes
This book gives general information. It isn't medical advice, and it's no substitute for a professional who knows your situation. NHS guidance is quoted as I found it in September 2026 and applies to England.
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 or correction notice in September 2026. I found no retractions. The 2016 Lancet paper by Ekelund and colleagues has a published erratum, which I haven't read. Where a chapter isn't listed, it rests on my own reasoning. That includes chapters 1, 10 apart from one trial, 12 and 16. You at fifty-four, Alfie, Denise and every other example are invented for illustration.
Before you start. The advice to speak to a GP before exercising is from the NHS page "Physical activity guidelines for adults aged 19 to 64". The advice on when to see a GP about tiredness is from the NHS page "Tiredness and fatigue". The 999 criteria are from the NHS page "Chest pain".
Chapter 2. The figures of more than seven hours for adults and ten hours or more for people over sixty-five, and the account of how daily life lost its movement, are from the NHS page "Why we should sit less". The figure of 70 to 85 per cent of working hours is from the background section of Edwardson and colleagues, "A three arm cluster randomised controlled trial to test the effectiveness and cost-effectiveness of the SMART Work & Life intervention for reducing daily sitting time in office workers: study protocol", BMC Public Health 18, 2018, article 1120. The list of reasons is mine.
Chapter 3. McGuire, Levine, Williamson, Snell, Blomqvist, Saltin and Mitchell, "A 30-year follow-up of the Dallas Bedrest and Training Study: I. Effect of age on the cardiovascular response to exercise", Circulation 104, 2001, pages 1350 to 1357. McGavock, Hastings, Snell, McGuire, Pacini, Levine and Mitchell, "A forty-year follow-up of the Dallas Bed Rest and Training study: the effect of age on the cardiovascular response to exercise in men", Journals of Gerontology Series A 64, 2009, pages 293 to 299. The 27 and 26 per cent figures are from the second paper. Kortebein, Symons, Ferrando, Paddon-Jones, Ronsen, Protas, Conger, Lombeida, Wolfe and Evans, "Functional impact of 10 days of bed rest in healthy older adults", Journals of Gerontology Series A 63, 2008, pages 1076 to 1081. Their scores on a standard test of everyday physical performance didn't change significantly, which I left out of the chapter for brevity. No study I know of has compared years of desk work with bed rest directly, so treating a sedentary day as a diluted form of bed rest is my inference. The account of the body maintaining what's used is a simplification of standard physiology.
Chapter 4. Thayer, "Energy, tiredness, and tension effects of a sugar snack versus moderate exercise", Journal of Personality and Social Psychology 52, 1987, pages 119 to 125. Eighteen volunteers took part over twelve days each. Puetz, O'Connor and Dishman, "Effects of chronic exercise on feelings of energy and fatigue: a quantitative synthesis", Psychological Bulletin 132, 2006, pages 866 to 876. The overall effect was 0.37 of a standard deviation, which is small to moderate, and as the chapter says, it disappeared in placebo-controlled trials of exercise alone. The idea that your sense of energy is a setting and not a gauge is my way of putting it.
Chapter 5. The description of why a still body feels stiff is a simplified outline and I haven't sourced it to a particular paper. The quotations on exercise and osteoarthritis are from the NHS page "Osteoarthritis, treatment". Roffey, Wai, Bishop, Kwon and Dagenais, "Causal assessment of occupational sitting and low back pain: results of a systematic review", Spine Journal 10, 2010, pages 252 to 261. The review covered sitting at work and found five high-quality studies. The warning signs for back pain are from the NHS page "Back pain", which lists more than I've given. The NHS page on rheumatoid arthritis says that the morning stiffness of osteoarthritis usually wears off within thirty minutes and that stiffness lasting longer can point to other kinds of arthritis.
Chapter 6. Ekelund, Steene-Johannessen, Brown, Fagerland, Owen, Powell, Bauman and Lee, "Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women", Lancet 388, 2016, pages 1302 to 1310. Thirteen studies with 1,005,791 people gave data on sitting, and six studies with 465,450 people gave data on television. The most active quarter reported more than 35.5 MET-hours a week, which the authors equate to about 60 to 75 minutes of moderate activity a day. The NHS quotation is from "Why we should sit less".
Chapter 7. 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, article l4570. There were 36,383 people and 2,149 deaths over a median of 5.8 years. Paluch and the Steps for Health Collaborative, "Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts", Lancet Public Health 7, 2022, pages e219 to e228. My estimate that the gap between the bottom two quarters is about twenty-five minutes of walking assumes roughly a hundred steps a minute. Stamatakis, Ahmadi, Gill, Thøgersen-Ntoumani, Gibala, Doherty and Hamer, "Association of wearable device-measured vigorous intermittent lifestyle physical activity with mortality", Nature Medicine 28, 2022, pages 2521 to 2529. The examples of what the bursts consisted of are mine, since the sensors record effort and not what people were doing. The NHS list of light activities is from "Physical activity guidelines for older adults".
Chapter 8. Dunstan, Kingwell, Larsen, Healy, Cerin, Hamilton, Shaw, Bertovic, Zimmet, Salmon and Owen, "Breaking up prolonged sitting reduces postprandial glucose and insulin responses", Diabetes Care 35, 2012, pages 976 to 983. The summary describes an initial two hours of sitting followed by five hours of measurement. The explanation in terms of large muscles taking up sugar is the standard one and isn't tested in this paper.
Chapter 9. Edwardson and fifteen colleagues, "Effectiveness of an intervention for reducing sitting time and improving health in office workers: three arm cluster randomised controlled trial", BMJ 378, 2022, article e069288. There were 78 office clusters. The summary lists work performance among the outcomes measured and reports no finding on it in either direction. The list of ways to fit breaks into work is mine, apart from the moved bins and printers, which the trial's protocol mentions.
Chapter 10. Edwardson and colleagues as above. That people in standing jobs have their own aches is common observation, and I haven't sourced it.
Chapter 11. Ekelund and colleagues 2016 and Dunstan and colleagues 2012, as above. The possible reasons why television time looks worse than other sitting are suggestions made in this field generally and aren't established. The suggestions for the evening are mine.
Chapter 13. McGuire, Levine, Williamson, Snell, Blomqvist, Saltin and Mitchell, "A 30-year follow-up of the Dallas Bedrest and Training Study: II. Effect of age on cardiovascular adaptation to exercise training", Circulation 104, 2001, pages 1358 to 1366. The summary calls it a six-month endurance training programme. That it consisted of walking, jogging and cycling is from my memory of the full paper. Fiatarone, O'Neill, Ryan, Clements, Solares, Nelson, Roberts, Kehayias, Lipsitz and Evans, "Exercise training and nutritional supplementation for physical frailty in very elderly people", New England Journal of Medicine 330, 1994, pages 1769 to 1775. The trial also tested a nutritional supplement, which had no effect. That the training was for the legs, three times a week, and that the home was in the United States, are from memory and not from the summary. Everything under what to expect is my expectation and not a finding.
Chapter 14. The test for moderate activity and the advice on strengthening activities are from the NHS adult guidelines page. 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 parts haven't been tested together. The half-hour interval is my choice.
Chapter 15. The driving advice is rule 91 of the Highway Code. The NHS pages used are "Fitness advice for wheelchair users", "Sitting exercises", "Osteoarthritis, treatment", "Back pain" for self-referral, and "Myalgic encephalomyelitis or chronic fatigue syndrome, treatment" for the statement on graded exercise therapy. I've extended that caution to long Covid on my own judgement, because many people with long Covid report the same worsening after exertion. The remarks on diabetes medicines and on dizziness are general advice, and your own clinician's view comes first.