The purpose of this study was to examine the effect of two family interventions targeting inactive children on their parents' MVPA. Correlates of MVPA across the trial in the form of theory of planned behavior (TPB) and multi-process action control (M-PAC) were examined as exploratory outcomes. Parents (of children aged 6-12 years) were randomized to either a planning + education (n = 52) or an education only condition (n = 50) designed to improve child MVPA. Parental MVPA (accelerometry, self-report) was assessed at baseline, 6-week, 13-week, and 26-week time-periods. Parental MVPA increased from baseline to 26 weeks (p < .05), but there were no group differences. The TPB was unable to predict MVPA and application of M-PAC showed this was because nearly all participants possessed the intention to be active. Successful-compared to unsuccessful-intenders had stronger habit in four of the six tests employed (p < .05). Parent MVPA may benefit during a family-based intervention but the putative mediators of this increase are unclear.Registered trial clinicaltrials.gov #NCT01882192.
Keywords: Action control; Exercise; Habit; Randomized trial; Theory of planned behavior.