Behavioural Theory

Active control text messages target autonomy, competence, and relatedness, which are three components of self-determination theory. The theory of expanded, extended and enhanced opportunities proposes that physical activity increases when people have more opportunities, more time, and higher-quality routine activity opportunities. The Theory of Planned Behaviour, which includes attitudes toward exercise, subjective norms, and perceived behavioural control, is embedded in the MOTAFIT intervention. The process evaluation uses the Durlak and DuPre Framework for Effective Implementation, which is specific to youth and adolescents, evaluating reach, dosage, fidelity, quality, responsiveness, adaptation, and differentiation. Psychosocial supports in the intervention are intended to promote motivation, self-efficacy, adherence, and sustained behaviour change rather than functioning as a separate behavioural-change programme.