Physical Activity Promotion for Breast and Endometrial Cancer Survivors

Inclusion Criteria: * Female adult (≥18 years of age) * Diagnosis of Stage I-III breast or Stage I-II Type 1 endometrial cancer within the past 5 years. * At least 3 months past completion of primary active treatment (i.e., surgery, chemotherapy, and/or radiation). May still be undergoing endocrine or Human epidermal growth factor receptor 2 (Her2) therapies. * Insufficiently active, defined as ≤60 min/week of MVPA, performed in bouts of ≥10 minutes.This is 40% of the recommended amount of MVPA based on the 2008 Federal Guidelines and the American Cancer Society's guidelines for cancer survivors. The 7-Day Recall will be used to screen for physical activity; eligibility will be confirmed prior to randomization using the ActiGraph accelerometer. * Able to access high-speed Internet daily at home on a computer, smartphone, or tablet. Internet access may be through a household connection or a wireless provider (e.g., Verizon, AT\&T). For compatibility with the Fitbit, the device must run a Windows, Apple, or Android operating system. * Have a MyChart account or be willing to create one. * Fluent in spoken and written English language. * For safety, participants will be screened using the Physical Activity Readiness Questionnaire (PAR-Q) and the Falls Risk Screener, which address joint and cardiovascular problems, balance issues, and other concerns. Physician consent will be obtained for all participants who meet the following criteria: * Answer yes to ≥1 question on the PAR-…