Abstract
BACKGROUND: Dual process models represent a useful framework for explaining physical activity (PA) in that behavior is explained by reflective (i.e., conscious, effortful) and automatic (i.e., unconscious, effortless) determinants. Yet the distinct momentary reflective and automatic determinants associated with PA adoption and maintenance are unclear. METHODS: Older adults (N = 202; ≥60 years) wore accelerometers to measure PA (i.e., moderate to vigorous intensity PA [MVPA], step counts) and completed brief mobile phone prompts assessing general reflective (i.e., demands, deliberation, self-efficacy, self-control, stress coping, emotion regulation), behavior-specific reflective (i.e., PA intentions, self-efficacy, planning), and automatic determinants (i.e., affect, physical and social context, functional stability of one's routine) as part of three, 2-week waves of data collection spaced over one year. Multilevel modeling was used to examine the within- and between-person associations between these determinants and subsequent PA. RESULTS: There were within- or between-person differences between general reflective, behavior specific, and automatic determinants and PA by adopter and maintainer status. General reflective determinants tended to be more predictive of step counts compared to MVPA. Within-person behavior-specific reflective determinants (i.e., intentions, self-efficacy, plans) were positively associated with PA behavior but associations tended to be more positive among PA maintainers. Automatic determinants were more predictive of the amount of PA as opposed to the likelihood of PA occurring. CONCLUSION: Reflective and automatic determinants, as well as the levels at which these determinants operate (i.e., between vs within), need to be considered when attempting to explain and predict the adoption and maintenance of PA.