Chapter 13 Public health

1. Chapter 13Public health

2. Chapter overview • Introduction • Recommendations for physical activity • Rationale for recommendations • Changing physical activity behaviours • Examples of good practice in public health • Walking: ‘The nearest to perfect exercise’ • Physically active commuting • Benefits versus risks • A ‘best buy in public health’? • Summary

3. Introduction • By 2030 non-communicable diseases, e.g. CVD, type 2 diabetes and many cancers, will contribute to 69% of deaths and 57% of the global burden of disease. • These diseases share a rather small number of preventable risk factors. • Some 80% of premature heart disease and stroke, 80% of type 2 diabetes and 40% of all cancers are preventable.

4. Population-attributable risk (PAR) for physical inactivity, Canada

5. Physical activity recommendations: adults • 30 minutes of moderate-intensity aerobic activity on five days each week or 20 minutesvigorous activity on three days; • moderate-intensity activities can be accumulated in bouts of 10 minutes; PLUS • activities that maintain or increase muscular strength and muscular endurance on at least two days each week; • more benefit is gained from exceeding these recommendations.

6. Recommendations: avoidance of weight gain and older adults • Prevention of unhealthy weight gain – 60 minutes moderate-to-vigorous on most days. • Older adults: • moderate-intensity related to individual level of aerobic fitness; • include activities to maintain or increase flexibility and balance; • activity plans should integrate preventive and therapeutic recommendations.

7. Recommendations: children • 60 minutes or more of at least moderate intensity, preferably daily; • 16,500 steps; • use of electronic media restricted; • some sessions that produce ‘high physical stress’. Note: There are some differences between countries.

8. Evidence providing rationale for recommendations • Frequent, preferably daily, activity – acute effects, e.g. on triglycerides, BP. • ‘Trading’ intensity for duration – triglycerides similarly decreased after two sessions of walking, one twice the duration at half the intensity. • Accumulating short bouts – triglycerides throughout day: decreased by similar amount with one 30-minute walk or three, ten-minute walks.

9. Acute effects of exercise – revealed by de-training studies

10. Trading intensity for duration

11. Accumulating ten-minute bouts: an example using triglycerides

12. Good practice: examples to facilitate active lifestyles • Built environment: the more attractive and ‘walkable’ streets and parks are, the higher levels of walking. • Denmark legislates that every child must have a safe route to school (50% of Danish children cycle or walk to school). • In the Netherlands motorized traffic entering residential zones is restricted to a speed of ‘walking pace’.

13. ‘Brisk’ walking at 3.5mileh–1 • Light activity for the average young person; • moderate for the majority of sedentary, middle-aged adults; • vigorous for the elderly or individuals whose functional capacity is limited by disease.

14. . . Importance of intensity relative to VO2max or VO2max reserve

15. . Concept of VO2max reserve • Definition: ‘Capacity above the resting metabolic rate of 1MET’. • Individuals with low VO2max reserve have little capability to increase oxygen uptake above the resting level. • For such people brisk, or even normal-paced walking constitutes vigorous exercise. .

16. Walking: epidemiology of health benefits Walking has been independently associated with a lower risk of: • all-cause mortality; • CHD/CVD; • ischaemic stroke; • type 2 diabetes; • cognitive decline in older people; • weight gain.

17. Summary I • Non-communicable diseases are a major and increasing public health burden. Increasing physical activity levels would have an important impact on the incidence of such diseases. • Adults need moderate-intensity activity for at least 30 minutes on five days each week, or vigorous-intensity aerobic activity for a minimum of 20 minutes on three days. Children need more. • Changes to the built environment that facilitate walking and cycling will have an impact on population physical activity levels

18. Summary II • Brisk or fast walking will improve fitness in most middle-aged and older men, and in almost all adult women. Walking for exercise is very injury-free. • Adverse side-effects of exercise are mainly avoided if intensity is moderate. For the majority of individuals, benefits outweigh risks. • For a society, the promotion of physical activity may lead to economic benefits