A Micro-randomized Trial of HeartSteps, an mHealth Intervention for Increasing Physical Activity

Study Overview
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Brief Summary
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The aim of this research is to evaluate the efficacy of contextually tailored activity suggestions and activity planning for increasing physical activity among sedentary adults.

Detailed Description
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Physical activity is a key behavioral strategy for prevention of non-communicable diseases such as diabetes and heart disease. Mobile health (mHealth) interventions have shown promise for supporting physical activity adoption and maintenance in ways that are highly acceptable to users, scalable, and cost-efficient. This study examines two intervention strategies-contextually tailored activity suggestions and daily planning of the activity for the next day-that a mobile health intervention can use to encourage physical activity in sedentary adults. Study participants use HeartSteps, an mHealth physical intervention developed by the research team, in their daily lives for six weeks. Over the course of the study both of the HeartSteps intervention components-contextually-tailored activity suggestions and activity planning-are micro-randomized for each participant on each of the day of the study, in order the effects on physical activity of each component separately and how those effects change over time. The primary hypothesis for suggestions is that providing a contextually tailored activity suggestion increases participant step count over the subsequent 30 minutes following message delivery. The first secondary hypothesis for suggestions is that the proximal effect of the contextually tailored activity suggestions on the subsequent 30-minute step count will decrease with duration in the study. The primary hypothesis for planning is that receiving evening planning will increase step count on the following day. The primary analyses will use the methods developed in Boruvka et al. (2017). The primary longitudinal outcome for activity suggestions will be the log of the step count in the 30 minutes subsequent to decision points. The log of the step count in the 30 minutes prior to randomization will be included as a control variable. The primary longitudinal outcome for planning will be the square root of the step count on the day following the randomization of planning treatment. All missing but available minute-by-minute step counts from the wrist band will be imputed as 0. See Allocation section for the definition of availability. Sensitivity analyses using step counts from the mobile phone (secondary data source) will be conducted.

Official Title
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HeartSteps: a Just-in-Time Adaptive Intervention for Increasing Physical Activity Amongst Sedentary Adults.

Conditions
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Physical Activity

Intervention / Treatment
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* Behavioral: HeartSteps: A just-in-time adaptive intervention for increasing physical activity amongst sedentary adults.


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: English speakers, between 18 and 60 years of age, could walk for exercise without discomfort, and either had a full-time daytime job or a regular schedule outside the home (e.g., students) have a personal phone running Android 5.0 or higher or willing to use a study-provided phone as their primary phone for the duration of the study. Exclusion Criteria: Need medical supervision to exercise Currently using an activity tracker (e.g., FitBit)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Interventional Model Description: Each participant-time point is randomized between intervention or no intervention (delivery of a contextually tailored activity suggestion or no suggestion; planning or no planning)
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: HeartSteps intervention<br>For activity suggestions, at each available decision time, each participant is randomly assigned to either receive an activity suggestion or not. The randomization probability is 0.6 for receiving a message and 0.4 for not receiving a message. For activity planning, at each decision point, the participant is randomized to either receive evening planning or not at that decision time. The randomization probability for receiving planning is 0.5, and 0.5 for not receiving planning. | Behavioral: HeartSteps: A just-in-time adaptive intervention for increasing physical activity amongst sedentary adults.<br>* HeartSteps is an Android-based mHealth intervention that contains two main intervention components: contextually-tailored suggestions for activity and planning of the next day's activity. Activity suggestions provide individuals with actionable suggestions for how they can be active in their current context. Delivered suggestions are tailored based on time of day, user's location, day of the week (weekend/weekday), and weather. HeartSteps can deliver a user activity suggestions up to five times a day. Evening planning asks users to create or choose a plan of how they will be active on the following day. Planning can be delivered once a day, in the evening.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 30 minute step count | 30-minute window after each available decision point | 30 minutes | 
| Daily step count | Daily step count on the day following treatment | 24 hour day | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Thumbs up/down | User ratings of message usefulness (thumbs up/thumbs down rating) | 30-minute window while message is available | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Physical Activity, Mobile Health, Self Monitoring, Wearable Sensors, Tailored Health Communication, Implementation Intentions, Mobile Apps, Anti-Sedentary Behavior, Opportunistic Physical Activity, Health Belief Model