Study of Aerobic Training for People Receiving Treatment for Breast Cancer

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