translate intentions into behaviour. Competence-based theories focus on perceptions of com-petence and confidence as a prime driver of behaviour, such as in self-efficacy approaches (Bandura 1997; McAuley and Blissmer 2000). Early attempts in exercise psychology favoured theories of perceived control, such as locus of control (Rotter 1966). These yielded small effects or were inadequately tested so researchers searched for other control-related constructs (Biddle 1999; Biddle and Mutrie 2001). One that has been popular is the self-determination theory advocated by Deci, Ryan and colleagues (Deci and Flaste 1995; Deci and Ryan 1985; Ryan and Deci 2000a, 2000b; Williams et al.2000), and applied to physical activity by others (Chatzisarantiset al.2003). Research shows that motivation for physical activity is likely to be more robust if it involves greater choice and self-determination rather than external control. In
addition, such an approach is likely to lead to feelings of higher well-being.