Micro-randomized trial · 2019
Efficacy of Contextually Tailored Suggestions for Physical Activity: A Micro-randomized Optimization Trial of HeartSteps
Klasnja P, Smith S, Seewald NJ, Lee A, Hall K, Luers B, Hekler EB, Murphy SA
What it found
Activity suggestions were randomly sent or withheld several times a day. A suggestion raised steps in the next 30 minutes by about 14% on average, a large effect at first that faded over the six weeks. Suggestions to go for a walk worked; suggestions to break up sitting showed no detectable effect.
Where the evidence stops
A small trial about physical activity. Strong as a method for testing whether to step in; weak as a rule for other behaviours.
How it shapes Pursue
Pursue
Shows that 'should we say something now?' can be tested moment by moment, and that effects fade, which is why Pursue is built to say less over time, not more.
A design input, not evidence that Pursue works.
Cited in
- 01When is the right moment for a reminder or a nudge?When the person is able to take it in, which changes from moment to moment. In a trial with 1,255 users of a workplace well-being app (Bidargaddi et al., 2018), the same message made people about 4% more likely to use the app in the next day, and about 12% more likely at 12:30 on weekends.Timing and receptivity
- 02Do reminder apps change what people do, or just how often they open the app?Often only the second. In a six-month University of Michigan trial with 287 adults with high blood pressure (Golbus et al., 2026), notifications made people use the app more but did not raise steps in the next hour or improve food choices the next day. Opening an app is engagement, not benefit.Engagement is not benefit