The YourMove Study: Optimizing Individualized and Adaptive mHealth Interventions Via Control Systems Engineering Methods

Strong evidence indicates physical activity (PA) reduces risk of bladder, breast, colon, endometrium, esophagus, gastric, and renal cancer, and there is moderate evidence for lung cancer. Individuals aged 25+ who are inactive are at high risk of developing a variety of cancers. Unfortunately, only 1/3 of adults meet guidelines for PA; thus, they are an important group to target. In response, the investigators developed JustWalk, a modular adaptive mobile health (mHealth) intervention that makes daily N-of-1 adjustments to support PA for each person. JustWalk can perform N-of-1 adaptation based on our innovative use of control engineering methods, which the investigators call a control optimization trial (COT). The YourMove study is a 12-month 2-arm randomized control trial (RCT) designed to assess the efficacy of COT methods in 386 adults aged 25+ who are inactive. The investigators will evaluate the differences in minutes/week of moderate-to-vigorous intensity PA (MVPA), measured via accelerometers, among the COT-optimized (intervention) vs. non-COT intervention designed in accordance with standard of care digital corporate wellness to support physical activity (control) groups at 12 months. The YourMove Study uses a fully integrated system of modalities that include: 1) a popular consumer-level wearable (e.g., Fitbit Versa) and corresponding app (e.g., the Fitbit app); 2) daily process-level analyses done using the Fitbit Versa and ecological momentary assessment (EMA) measures rooted in social cognitive theory (SCT) constructs to promote behavior change; 3) a highly tailored text messaging system encouraging participants to achieve recommended minutes of physical activity: \>150 minutes per week of moderate-to-vigorous physical activity (MVPA); and 4) a self-study tool called "Reflect", which is meant to support individuals in self-experimentation to identify strategies that work for them to fit regular MVPA into their lives. The consumer-level devices and app will be used to self-monitor behavior, and their data will be passively acquired in real-time. A variety of self-reported measures asked daily via EMA enables the measurement of psychosocial factors important for the development of a dynamical SCT model and produces ambitious yet achievable step goals that are adaptive to each individual. Algorithms will be used to automatically deliver text messages to support individually tailored goal setting, performance feedback, and goal review in a highly dynamic style that reflects participants' behavioral progress towards achieving a minimum goal of 150 min/week of MVPA.