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

The purpose of this study is to determine the efficacy of a new digital health tool that uses a phone and smartwatch to encourage physical activity and increase weekly amounts of Moderate to Vigorous Physical Activity (MVPA) over 12 months among adults compared to a digital health intervention that mimics a standard of care corporate wellness program.

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.

Eligibility Criteria:
Inclusion Criteria:

* Age 25-80 years old
* Intend to be available for a 12-month intervention
* Willing and able to attend 3 measurement visits over 12-months
* Willing and able to use a smartphone and text messaging
* Willing and able to use the wearable and corresponding app
* Willing and able to walk and engage in moderate-intensity physical activity
* Healthy enough to participate based on the Physical Activity Readiness Questionnaire
* BMI between 18-40 kg/m\^2

Exclusion Criteria:

* Psychiatric or medical conditions that prohibit compliance with the study protocol
* Enrolled in or planning to enroll in a physical activity program during the study period
* Those with a mechanical medical implant, such as a pacemaker