Study Design
We designed a fully remote RCT to test the effectiveness of the experimental version of TreadWill compared with an active control version and a waitlist control version. We planned to recruit 600 participants with a 1:1:1 distribution across the 3 groups. We implemented simple randomization using an automated randomization function (developed in Python; version 3.4.3; Python Software Foundation). This trial was registered at ClinicalTrials.gov before commencement (NCT03445598).