Schematic of randomization for the Activity Suggestions component in the Heart Steps micro-randomized trial (MRT). In each of the 42 days of the experiment, at each prespecified time of randomization, tm, where m = 1 to 5, an assessment was made of whether the intervention was disabled, or the participant was driving or walking. If any of these was “yes,” no randomization was performed. Otherwise, the individual was randomized to be shown a walking activity suggestion (p=.30), anti-sedentary suggestion (p=.30), or no suggestion (p=.40).