StandUPTV: A full-factorial optimization trial to reduce sedentary screen time among adults.

Background: Using the multiphase optimization strategy (MOST) framework, we aimed to identify a feasible, acceptable and optimized set of mHealth-delivered behavioral strategies for reducing recreational sedentary screen time (rSST) by at least 60 min/day. Methods: Eligible participants were 23-64 years old and had high rSST (> 3 h/day). We used a full factorial (23) design in which participants received a "core" mHealth application and were randomized to combinations of three components (on vs. off): LOCKOUT: rSST electronically restricted; TEXT: rSST reduction prompts; and EARN: rSST through physical activity. rSST was assessed at baseline and at 8 and 16 weeks of age via an integrated measure of sedentary time and screen time. We used a linear mixed effect model to test the change in rSST for the three intervention components and their interactions. Results: A total of 82% of the randomized participants (N = 110) were female, with a mean ± SD age of 41 ± 11.7 y and a BMI of 29.7 ± 7.8 kg/m Conclusions: We identified several promising intervention versions that exceeded our optimization objective. The intervention version that included core, LOCKOUT, TEXT, & EARN components "on" was efficacious, feasible and acceptable and should be used to test the effect of rSST reductions on health outcomes. Trial registration: (clinicaltrials.gov NCT04464993).