Pilot SMART of a Remotely Delivered, Physical Activity Intervention for Breast Cancer Survivors

The goal of this clinical trial is to evaluate the feasibility of randomizing participants to a "step-up" intervention pathway when they perform \150 minutes accelerometer measured MVPA/week at the intervention mid-point (week 6-data collection burst) and end-of-study (week 12-data collection burst)? 4. Do at least 50% of participants assigned to the "step-up" intervention pathway achieve a clinically meaningful volume of weekly MVPA by 12-weeks follow-up? All participants will: * Be assigned to either the Affect-based exercise prescription or the Effort-based exercise prescription. * Participate in three meetings with the interventionist (an exercise specialist) meant to help them get started increasing weekly exercise. These meetings are the same for all participants. * Be asked to wear an activity monitor and respond to brief surveys for 10 consecutive days at 4 points in time: Baseline, 2weeks, 6weeks, and 12weeks. Some participants (those performing \<150 minutes of MVPA at the 6-week data collection burst) will be assigned to the step-up intervention pathway. Participants assigned to the step-up intervention pathway will complete 3 additional follow-up meetings with the interventionist. During these meetings, the interventionist will help participants identify opportunities to be more active, set goals