ABSTRACT
Sedentary behaviour is, essentially, ‘sitting time’. As de ned in Chapter 1 it refers to ‘any waking behaviour characterized by an energy expenditure ≤1.5 METs while in a sitting or reclining posture’ (Sedentary Behaviour Research Network, 2012). Typical examples include TV viewing, computer use, sitting at work or in school, and car travel. Under this de nition behaviour performed while standing may be thought of as non-sedentary. It is possible to meet recommended levels of physical activity (e.g. 150 minutes of MVPA per week for adults), and be classi ed as ‘active’, but at the same time take part in high levels of sedentary behaviour. That is, the two behaviours may coexist. Furthermore, while the relationship between sedentary behaviour and physical activity in young people has been shown to be negative (r = -0.108) in a meta-analysis of 163 studies, the small size of the relationship suggests that these behaviours do not directly displace each other (Pearson et al., 2014). This means that it is important not to refer to those with low levels of physical activity as ‘sedentary’, as is often the case in the literature. Instead, we should use the term ‘inactive’. Figure 16.1 is a depiction of a continuum of energy expenditure and posture whereby ‘light physical activity’ (e.g. light ambulation, but not moderate physical activity) falls between sedentary behaviour and MVPA. This helps to see how sedentary behaviour and light PA are likely to easily substitute for each other (i.e. when not sitting there is a good chance you are in light PA, such as standing), but less likely to be in moderate or vigorous PA. Recognising physical activity and sedentary behaviour as distinct behaviours is important from the point of view of psychology and behaviour change. As they are di erent behaviours it is likely that they will be in uenced by di erent factors (correlates) and therefore may
368 Sedentary behaviour
require dierent behaviour change theories, frameworks and intervention approaches to facilitate change. In this chapter we follow the behavioural epidemiological framework (see Chapter 1) and explore the following key questions with respect to sedentary behaviour:
● What is the relationship between sedentary behaviour and health outcomes in young people and adults?
