Random Assignment of Intervention Messages for Developing Personalized Decision Rules to Promote Physical Activity

Phase 1

Completed

Brief Summary: Our goal is to develop personalized decision rules for selecting the frequency, timing, and content of messages to promote physical activity. The objective of this project is to develop personalized dynamical models of physical activity (PA) under different weather and temporal conditions as well as in response to different types of intervention messages. This approach relies on having extensive observations within the person under varying conditions to develop a dynamical model of how different conditions interact with each other to predict how behavior changes in response to text messages. Complementary sub-models will be estimated for each participant to describe their behavioral responses under different weather conditions. Healthy but insufficiently active young adults (n=80) will wear an activity monitor and receive a variety of randomly-timed and randomly-selected notifications via smartphone. GPS coordinates at the time of messages delivery and receipt are recorded and used to look up weather indices at that location at that time. The work is exploratory/descriptive as we will be developing models to describe participants' responses to messages under different weather conditions. This work is needed to develop the decision rules for a subsequent behavioral intervention that will be developed and tested in a future project.

Recruitment & Eligibility

Inclusion Criteria

Participants capable of reading, speaking and understanding English and of giving informed consent.
Participants between the ages of 18-29 years.
Participants must be free of visual impairment that would interfere with the use of a smartphone.
Participants must own and carry an iPhone (running iOS version 10 or higher) or Android (running operating system 7 or higher) smartphone during waking hours.

Exclusion Criteria

Participants engaging in 90 or more minutes of moderate- or greater intensity PA each week.
Participants engaged in organized programs with mandated physical activity (e.g., varsity sports, ROTC).
Participants with contraindications to normal physical activity on the Physical Activity Readiness Questionnaire.
Participants who require an assistive device for mobility or have any other condition that may limit or prevent participation in moderate-intensity physical activity.
Participants who are pregnant or planning to become pregnant within the next 6 months.
Participants with a prior diagnosis of cancer, cardiovascular disease, diabetes or metabolic syndrome.

Arm && Interventions

Group	Intervention	Description
Random Messaging	Short Message with Text and Optional Image	Participants receive 0-5 messages/day from the Random AIM app. Messages are only delivered outside of a participant-specific Do Not Disturb window (e.g., 11pm-8am). Messages are selected randomly from three content domains: Move More (40%), Sit Less (40%), and Inspirational Quotes Unrelated to Movement (20%). Half of the messages are accompanied by images. Message selection and timing are determined randomly each night for the following day.

Primary Outcome Measures

Name	Time	Method
Change in Moderate (or Higher) Physical Activity Duration Following Message Receipt	15-minute epochs for the remainder of the walking day	Fitbit-assessed minutes with step counts \>= 100 steps/min in 15-minute epochs (steady states represent the change in expected step counts if a message was delivered versus if the message was not delivered)

Secondary Outcome Measures