Chapter 13 Public health

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

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.

Population-attributable risk (PAR) for physical inactivity, Canada DiseasePAR (%) Coronary artery/heart disease19.4 Stroke24.3 Hypertension13.8 Colon cancer18.0 Breast cancer14.2 Type 2 diabetes21.1 Osteoporosis24.0

Physical activity recommendations: adults  30 minutes of moderate-intensity aerobic activity on five days each week or  20 minutes vigorous 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.

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.

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.

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.

Acute effects of exercise – revealed by de-training studies

Trading intensity for duration

Accumulating ten-minute bouts: an example using triglycerides

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’.

‘Brisk’ walking at 3.5 mile h –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.

Importance of intensity relative to VO 2 max or VO 2 max reserve..

Concept of VO 2 max reserve Definition: ‘Capacity above the resting metabolic rate of 1 MET’. Individuals with low VO 2 max reserve have little capability to increase oxygen uptake above the resting level. For such people brisk, or even normal-paced walking constitutes vigorous exercise...

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.

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

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