Overview

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 of MVPA at the 6-week data collection burst. Participants who performed \<150 minutes of MVPA at the 6-week data collection burst will be randomized to either continue with the standard intervention or advance to the step-up intervention. The main questions it aims to answer are:

1. What percentage of participants who are eligible for the intervention phase enroll in the intervention phase?
2. Will participants assigned to the "step-up" intervention pathway demonstrate equal or greater rates of study retention and intervention engagement relative to those assigned to the standard intervention arm?
3. What percentage of the sample is performing \>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, and problem solve barriers to action.

Eligibility

Inclusion Criteria:

-≥18 years old

• Within 5 years of completing primary cancer treatment (surgery, chemotherapy, and radiation) for Stage 0-III breast cancer
• \<60 mins/week moderate-vigorous physical activity (MVPA) with no major changes for the past 6- months
• Own an Android or iPhone smartphone (or tablet) and willing to use it to complete app-based surveys during assessment periods
• Willing to wear the ActiGraph monitor during assessment periods
• Access to internet to complete REDCap survey assessments

Exclusion Criteria:

• Non-English speaking/not able to read English
• Evidence of major contraindications for exercise (informed by the 2020 Physical Activity Readiness-Questionnaire (PAR-Q)+)
• Currently pregnant
• History of severe mental illness or currently taking mood stabilizing medications (antipsychotics, anticonvulsants, or lithium)
• Evidence of moderate-severe depressive symptoms (indicated by a score≥ 10 on the Patient Health Questionnaire-8)
• Evidence of moderate-severe cognitive impairment (indicated by a score \< 3 on a 6-item cognitive screener)
• Evidence of clinically significant substance use as indicated by a score of ≥ 2 on the CAGE- AID screener.