Efficacy of Contextually Tailored Suggestions for Physical Activity: A Micro-randomized Optimization Trial of HeartSteps.
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Background HeartSteps is an mHealth intervention that encourages regular walking via activity suggestions tailored to the individuals current context Purpose We conducted a micro randomized trial MRT to evaluate the efficacy of HeartSteps activity suggestions to optimize the intervention Methods We conducted a 6 week MRT with 44 adults Contextually tailored suggestions could be delivered up to five times per day at user selected times At each of these five times for each participant on each day of the study HeartSteps randomized whether to provide an activity suggestion and if so whether to provide a walking or an antisedentary suggestion We used a centered and weighted least squares method to analyze the effect of suggestions on the 30 min step count following suggestion randomization Results Averaging over study days and types of activity suggestions delivering a suggestion versus no suggestion increased the 30 min step count by 14 p 06 35 additional steps over the 253 step average The effect was not evenly distributed in time Providing any type of suggestion versus no suggestion initially increased the step count by 66 167 steps p Under 01 but this effect diminished over time Averaging over study days delivering a walking suggestion versus no suggestion increased the average step count by 24 59 steps p 02 This increase was greater at the start of study 107 or 271 additional steps p Under 01 but decreased over time Antisedentary suggestions had no detectable effect on the 30 min step count Conclusion Contextually tailored walking suggestions are a promising way of initiating bouts of walking throughout the day Clinical Trial information This study was registered on ClinicalTrials gov number NCT03225521