Inclusion Criteria:  Midlife status (age 45-64 at enrollment). Low baseline physical activity (≤150 minutes/week of MVPA]) as initially self-reported via the well-validated IPAQ and then confirmed via accelerometer after 7 days of wear.  Exclusion Criteria:  Existing coronary artery disease (CAD; diagnosed via cardiac catheterization using standard coronary artery stenosis definitions or prior ACS). An unrelated condition limiting physical activity (e.g., ambulation with a cane or walker, recent or planned surgery, or other condition such that ability to increase moderate to physical activity would be limited). Participation in any other programs focused on cardiac prevention or well-being (e.g., cardiac rehabilitation). A cognitive disturbance precluding participation or informed consent, assessed using a six-item screen7 designed to assess suitability for research participation. Inability to speak/write fluently in English. No access to a text message-capable phone.