In this study, investigators will compare standard Aerobic Training/AT with adaptive Aerobic Training/AT. Standard AT will be a fixed (unchanging) amount of walking each week, while adaptive AT will adjust the level of exercise depending on participants' response to the exercise. Investigators will see how both study approaches (standard AT and adaptive AT) affect participants' CRF.

Inclusion Criteria:

• Aged ≥18 years

• Female

• Diagnosed with primary breast cancer as defined by one of the following:

  • Histological confirmation
  • As per standard of care imaging

• Scheduled to receive neoadjuvant/adjuvant systemic and/or locoregional therapy

• Performing ≤90 minutes of moderate- and/or strenuous-intensity exercise per week, as evaluated by self-report

• Willingness to comply with all study-related procedures

• Able to achieve an acceptable peak baseline CPET, as defined by any of the following criteria:

  1. Achieving a plateau in oxygen consumption, concurrent with an increase in power output;
  2. A respiratory exchange ratio ≥ 1.10;
  3. Attainment of maximal predicted heart rate (HRmax) (i.e., within 10 bpm of age-predicted HRmax [HRmax = 220-Age[years]);
  4. Volitional exhaustion, as measured by a rating of perceived exertion (RPE) ≥ 18 on the BORG scale.

Exclusion Criteria:

• Enrollment onto any other interventional investigational study, except interventions determined by the PI not to confound study outcomes

• Receiving treatment for any other diagnosis of invasive cancer

• Distant metastatic malignancy of any kind

• Mental impairment leading to inability to cooperate

• Any of the following contraindications to cardiopulmonary exercise testing:

  i. Acute myocardial infarction within 3-5 days of any planned study procedures; ii. Unstable angina; iii. Uncontrolled arrhythmia causing symptoms or hemodynamic compromise; iv. Recurrent syncope; v. Active endocarditis; vi. Acute myocarditis or pericarditis; vii. Symptomatic severe aortic stenosis; viii. Uncontrolled heart failure; ix. Acute pulmonary embolus or pulmonary infarction within 3 months of any planned study procedures; x. Thrombosis of lower extremities; xi. Suspected dissecting aneurysm; xii. Uncontrolled asthma; xiii. Pulmonary edema; xiv. Respiratory failure; xv. Acute non-cardiopulmonary disorders that may affect exercise performance or be aggravated by exercise (i.e., infection, renal failure, thyrotoxicosis) xvi. Room air desaturation at rest ≤ 85%

• Any other condition or intercurrent illness that, in the opinion of the investigator, makes the subject a poor candidate for study participation](streamdown:incomplete-link)

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.