Introduction

Participation in physical activity is associated with significant benefits to health, most importantly in the prevention of Type 2 diabetes, cardiovascular disease and some cancers (Bauman et al., 2002; United States Department of Health and Human Services [USDHHS], 1996). In this chapter, we provide an overview of research on health-enhancing physical activity in adults. We provide brief examples of epidemiological studies on the relationships of physical activity to health outcomes: we also consider descriptive studies of adult populations on levels of participation. Our focus is on physical activity as a set of behaviours: we describe research findings on the ‘determinants’ of physical activity and describe the theories of health behaviour that are now widely used in understanding and influencing physical activity.

Physical activity exercise and fitness

The terms, ‘physical activity’, ‘exercise’ and ‘fitness’ are sometimes used interchangeably and at times incorrectly (Sallis & Owen, 1999). ‘Physical activity’ refers to any bodily movement, but generally to the movements of groups of large muscles (particularly of the legs and arms) that result in significant increases in metabolic energy expenditure, above the resting level. Regularly taking part in such activities is associated with better health outcomes. Physical activity can be performed at a wide range of intensities: walking or other moderate-intensity activities such as swimming at a low, moderate or brisk pace; vigorous endurance activities (for example, jogging or running, walking fast uphill, riding a bicycle fast or in hilly terrain); and activities that increase strength and/or flexibility (for example, weight training, calisthenics or strenuous occupational or domestic tasks such as heavy lifting or carrying).