Testing Responses of Young Adults to Intervention Messages for Promoting Physical Activity Trial

Education about health benefits of physical activity, 2018 US Physical Activity Guidelines, assigned goals tailored to baseline step counts, and worksheet to develop action and coping plans (three of each)

Fitbit activity tracker and mobile app to provide ad libitum behavioral feedback and self-regulatory support

Four text messages/day at random times within a participant's availability window and drawn at random from one of three content libraries (move more \[40%\], sit less \[40%\], inspirational quotes \[20%\])

Up to four text messages/day within a participant's availability window, timed and selected from one of three content libraries (move more, sit less, inspirational quotes) based on a person-specific dynamic model and contextual data