UC Merced

Although regular participation in physical activity is associated with physical and psychological health benefits in adolescents, few adolescents meet guideline physical activity levels highlighting the need for intervention. Interventions promoting physical activity in this population should target modifiable theory-based constructs and associated processes. We applied a unique integrated social cognition model to identify the theory-based constructs and processes that relate to physical activity intentions in two samples of Finnish adolescents. Participants from the Liitu 2018 study (n=455) completed self-report measures of social cognition constructs from theory of planned behavior, habit, self-discipline, past and current physical activity. Participants from the Liitu 2020 study (n=3,878) completed identical measures and measures of socio- structural and environmental factors. Participants from the Liitu 2018 study also wore accelerometers for one week concurrent with self-report measures. Hypothesized model effects were tested in the Liitu 2018 study sample and subsequently confirmed in a pre-registered analysis of the Liitu 2020 study sample. Across both samples, habit, attitude, perceived behavioral control, and self-reported past behavior predicted physical activity intention. Effects of self-reported past behavior on intention were partially mediated by the social cognition constructs; in contrast, effects of accelerometer-based physical activity were small. Effects of socio-structural and environmental factors on intention in the Liitu 2020 study sample were partially mediated by the social cognition constructs. Results corroborate beliefs and habit as consistent correlates of adolescents’ physical activity intentions, and provide initial evidence that social cognition constructs account for effects of socio-structural and environmental factors on intentions.