Changing Sedentary Behavior in the Office: A Randomised Controlled Trial Comparing the Effect of Affective, Instrumental, and Self-Regulatory Messaging on Sitting.

BACKGROUND: Although avoiding sedentary behavior has many health benefits, adults often sit for long periods at work. The purpose of this study was to compare affective attitude, instrumental attitude, and self-regulation messaging interventions on sitting in the workplace. METHODS: Using a cluster randomised controlled trial design, participants (N = 116) were assigned (by workplace) to: (a) instrumental, (b) affective, (c) self-regulation, or (d) control (nutrition information) groups. Measurements were taken online at baseline, 4 weeks, 8 weeks, and 12 weeks post-baseline. The interventions comprised three presentations delivered following baseline, week 4, and week 8 assessments. The primary outcome was self-reported average hours of sitting per day at work (registered trial number: NCT04082624). RESULTS: Controlling for baseline sitting, overall, the affective group sat for less time than the instrumental and self-regulation groups. Also, at week 4, the affective group sat for less time than the instrumental and self-regulation groups and, at week 8, the affective group sat for less time than the self-regulation and control groups. There were no differences between the groups at week 12. CONCLUSIONS: This investigation showed that workplace interventions targeting affective attitude can lead to less sitting time in the short term. Future research should explore additional strategies to minimise sedentary behavior in the long term.