Social cognitive correlates of physical activity across 12 months in cohort samples of couples without children, expecting their first child, and expecting their second child

Objective: The onset of parenthood has been identified as a critical risk period for physical inactivity, yet limited research has examined the correlates of physical activity (PA) using theoretical models in longitudinal designs with comparison groups of couples without children. The purpose of this study was to predict PA across 12 months among cohorts of couples with and without children using the theory of planned behavior (TPB). Method: Participants were 314 adults (102 not expecting a child, 136 expecting first child, and 76 expecting second child) who completed baseline demographics, measures of the TPB, and 7-day accelerometry, followed by assessments at six and 12 months. Results: Hierarchical linear modeling showed some TPB relationships were moderated by parental status and gender. Most notable, time-varying covariate analyses showed perceived behavioral control and intention decreased for new mothers compared to women without children across time. PA was predicted by intention for all cohorts, and intention was predicted by affective and instrumental attitudes and perceived behavioral control for husbands and wives, whereas subjective norm predicted intention only in husbands. For wives, the relationship between intention and instrumental attitudes and perception of behavioral control varied by parental status, and was larger for couples without children compared to second-time parents. Overall, there was considerable coordination in slopes and intercepts among couples, yet individual cognitions were better predictors than partner cognitions. Conclusion: The findings provide helpful information for targeting PA interventions among young adults, and suggest that interventions for new mothers may require greater effort to raise the absolute values of control when compared to women without children.