Exercise in Metastatic Breast Cancer: EMBody

Inclusion Criteria:

1. Age ≥ 18 years
2. Diagnosis of metastatic breast cancer
3. No progression of disease in the 12 months prior to screening per the treating investigator

   1. If participant has changed treatments in the prior 12 months for reasons other than progressive disease, they remain eligible
   2. Participants on no treatment or "no evidence of disease" but still with a diagnosis of metastatic breast cancer are eligible
4. ECOG performance status of 0-2
5. Ability to walk on a treadmill without assistive device.
6. Informed consent and authorization of the release of health information must be obtained according to institutional guidelines
7. Currently not meeting physical activity guidelines (defined as less than 150 minutes of moderate to vigorous exercise per week measured by the IPAQ questionnaire administered during screening)
8. Participants should have a cellular device compatible with iOS 15 or Android operating system 7.

Exclusion Criteria:

1. Receiving cytotoxic chemotherapy at any point in the prior 12 months.

   1. Participants receiving endocrine therapy are eligible.
   2. Participants receiving targeted therapy or antibody therapy are eligible (examples including trastuzumab, pertuzumab, TDM-1, trastuzumab deruxtecan, sacituzumab govetecan, immunotherapy, CDK4/6 inhibitors, olaparib, alpelisib, etc.)
2. Any condition precluding supervised exercise participation. A letter from a physician supporting participation can supersede this eligibility criteria.

   * NYHA class III or IV congestive heart failure
   * Uncontrolled angina
   * Myocardial infarction in the prior 12 months
   * Orthopedic surgery in the previous 3 months or plans for orthopedic surgery during the study period
   * Chronic uncontrolled pulmonary conditions such as uncontrolled asthma (symptoms \> 2 days/week) or dyspnea requiring oxygen
   * Symptomatic peripheral vascular disease
   * Or any other comorbidity that would interfere with the ability to complete and comply with the protocol in the opinion of the investigator, including psychological illness
   * History of fragility fracture
3. Active, untreated brain metastases