Documentation of the potential physical and psychological effects of participation in physical activity and exercise is now quite extensive (Bouchard et al., 1990). However, despite a widespread awareness of these benefits, population estimates for industrialized nations suggest that involvement in physical activity and exercise that is likely to produce cardiovascular benefit remains a minority pursuit (Stephens, Jacobs & White, 1985). The prevalence of involvement in activity levels that might impact on other aspects of fitness or wider parameters of physical health remains unknown, as does the level of involvement that affects mental health. It is considered a research priority, therefore, to identify the factors influencing the adoption and maintenance of physical activity and exercise. This is usually termed ‘exercise adherence’ (Biddle & Fox, 1989; Dishman, 1988a).

The purpose of this chapter is to summarize the current knowledge on the likely psychological correlates or proposed ‘determinants’ of participation in physical activity and exercise. Physical activity (PA) will be used to refer to all muscular–skeletal movement that results in energy expenditure, thus being an all-encompassing category including exercise and sport, as well as low-intensity movement not usually associated with overt gains in ‘fitness’. Exercise, however, will be used to refer to structured forms of PA that are usually participated in for reasons of gaining, maintaining or improving fitness (Caspersen, Powell & Christenson, 1985), and therefore is often of a moderately vigorous or vigorous nature.