Motivating Activity Through Text Communications - Helping Adults Increase Movement

Inclusion Criteria: * Be 40 years of age or older * Own a smartphone running an Android or iOS operating system * Have proficiency with the English language * Be capable of providing informed consent * Be able to perform moderate physical activity without restrictions * Be willing to complete the entire 6-month protocol * Be willing to establish a 12-hour window - beginning no later than 9:45 am and ending no later than 9:45 pm - for receiving text messages. Exclusion Criteria: * Residing outside of the continental United States * Self-reporting 90 minutes or more of moderate-to-vigorous intensity physical activity per week * contraindications to normal physical activity as identified on the Physical Activity Readiness Questionnaire (PAR-Q) * Mobility restrictions that interfere with unassisted physical activity * Being pregnant or planning to become pregnant during the study * Planning to undergo surgery during the course of the study protocol * Having a prior diagnosis of Alzheimer's disease or a related dementia * Evidence of mild cognitive impairment as indicated by a mini-Montreal Cognitive Assessment (MoCA) test score of 12 or higher * Concurrent participation in another study involving weight loss or physical activity * Failure to respond to at least 85% of Ecological Momentary Assessment (EMA) prompts during the 7-day qualification phase.