This is a 3-month physical activity intervention aimed to increase moderate-intensity activity among previously inactive breast cancer survivors. Participants will be eligible if they are not currently active, and have recently been diagnosed with breast cancer. Upon eligibility, participants will be randomized into one of two groups. The intervention group will receive weekly guidance from a peer coach to increase their activity throughout the three month intervention. The control group will be encouraged to self-monitor their physical activity throughout the three month intervention. Both groups will receive a Fitbit. Peer coaches will be trained to deliver the physical activity program using a web-based platform; all calls will be virtual. Participants will be assessed before and after the intervention.

Participants:

Inclusion Criteria:

• Diagnosed in the past 5 years with Stage 0-3 breast cancer
• Able to read and speak English
• Ambulatory
• Sedentary (<30 minutes of vigorous-intensity physical activity, <90 min of moderate-intensity physical activity in the past 6 months)
• Able to walk unassisted
• Access to a smartphone with Bluetooth and internet

Exclusion Criteria:

• Stage 4 cancer
• Medical or psychiatric problem that may interfere with protocol adherence

Peer Mentor Coaches:

Inclusion criteria:

• Current peer coach (at least one year)
• Have a valid email address, telephone access, and access to a tablet/computer
• Willing to participate in group training
• Willing to be supervised using platform
• Currently exercise for at least 60 min/week of moderate-intensity activity

Data can be shared upon request.