Abstract
ObjectivesPhysical activity declines during adolescence. The Theory of Planned Behaviour (TPB) is a useful framework for investigating activity but leaves variance unexplained. We explored the utility of a dual‐process approach using the TPB and the Prototype Willingness Model (PWM) to investigate correlates of physical activity, and 1‐year change in physical activity, among a large sample of adolescents.DesignA cross‐sectional and longitudinal analysis of baseline and follow‐up data from the Fit to Study cluster‐randomized trial.MethodsA total of 9,699 secondary school pupils at baseline and 4,632 at follow‐up (mean age = 12.5 years) completed measures of past week physical activity and constructs from both behaviour‐change models, at time‐points 1 year apart. Cross‐sectional analyses used multilevel, stepwise regression models to measure the strength of associations between model constructs and physical activity, and variance in behaviour explained by PWM over and above TPB. In longitudinal analyses, change scores were calculated by subtracting follow‐up from baseline scores. Models controlling for trial treatment status measured the strength of associations between change scores, and variance explained.ResultsAt baseline, after controlling for past behaviour, physically active prototype similarity had the strongest relationship with activity after the intention to be active. Change in prototype similarity had the strongest relationship with change in activity after the change in intention and attitudes. Prototype perceptions and willingness explained additional variance in behaviour.ConclusionA dual‐process model incorporating prototype perceptions could more usefully predict physical activity than models based on rational expectations alone. Behaviour‐change interventions promoting an active self‐image could be tested for effects on physical activity.
Highlights
Rapid psychosocial development during early adolescence can lead to lasting changes in health behaviours, including physical activity (Dahl, Allen, Wilbrecht, & Suleiman, 2018; Inchley et al, 2016)
The Theory of Planned Behaviour (TPB; Ajzen, 1985), has been widely used for investigating physical activity (Ajzen & Schmidt, 2020; Buchan, Ollis, Thomas, & Baker, 2012): behaviour is determined by reflective intentions, which are a product of attitudes, subjective norms, and perceived behavioural control (PBC; ability to perform the behaviour), which is governed in turn by beliefs about self-efficacy and control
We investigated physical activity behaviour-change during adolescence by examining longitudinal relationships: here, we aimed to measure the relative strength of associations between change in physical activity and change in TPB and Prototype Willingness Model (PWM) constructs, and the variance explained by the change in PWM variables over and above change in TPB variables
Summary
Rapid psychosocial development during early adolescence can lead to lasting changes in health behaviours, including physical activity (Dahl, Allen, Wilbrecht, & Suleiman, 2018; Inchley et al, 2016). The theory of planned behaviour The dominant behaviour-change theories for investigating physical activity have been in the social cognitive tradition, which assumes decisions are based on rational expectations of behavioural outcomes (Rhodes, McEwan, & Rebar, 2019) One such model, the Theory of Planned Behaviour (TPB; Ajzen, 1985), has been widely used for investigating physical activity (Ajzen & Schmidt, 2020; Buchan, Ollis, Thomas, & Baker, 2012): behaviour is determined by reflective intentions, which are a product of attitudes (evaluation of a behaviour), subjective norms (perceived social pressure to perform the behaviour), and perceived behavioural control (PBC; ability to perform the behaviour), which is governed in turn by beliefs about self-efficacy (capacity) and control (degree of autonomy to perform the behaviour; Conner & Sparks, 2005). Research has attempted to extend the TPB by exploring potential moderators of the intention-physical activity relationship, including both reflective factors such as affective attitudes and anticipated regret, and more automatic processes such as habit and self-regulation (Rhodes, Cox, & Sayar, 2021)
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