Supervised Aerobic Training During or After Chemotherapy for Operable Breast Cancer

Inclusion Criteria: * Aged 21-80 years * Female * MSK histologically confirmed early-stage operable breast cancer * Scheduled to receive chemotherapy in the neoadjuvant or adjuvant setting * ECOG status of 0 or 1 * Performing less than 150 minutes of structured moderate-intensity or strenuous intensity exercise per week * If a female of child-bearing potential, must not be pregnant or planning to become pregnant during the study. a. Women \< 50 years old must have a negative pregnancy test (urine HCG or serum βHCG) within 2 weeks of beginning chemotherapy. * Able to complete an acceptable baseline cardiopulmonary exercise test (CPET), in the absence of high risk ECG findings or other inappropriate response to exercise as determined by the investigator. * Able to achieve an acceptable peak baseline CPET, as defined by any of the following criteria: * Achieving a plateau in oxygen consumption, concurrent with an increase in power output; * A respiratory exchange ratio ≥ 1.10; * Attainment of maximal predicted heart rate (HRmax) (i.e., within 10 bpm of age-predicted HRmax \[HRmax = 220-Age\[years\]); * Volitional exhaustion, as measured by a rating of perceived exertion (RPE) ≥ 18 on the BORG scale. * Willingness to be randomized to one of the study arms Exclusion Criteria: * Presence of any other concurrent, actively treated malignancy * History of any other malignancy treated within the past 3 years (other than non-melanoma skin cancer) * Presence of metastatic disease * Any of the following contraindications to cardiopulmonary exercise testing: * Acute myocardial infarction within 3-5 days of any planned study procedures) * Unstable angina * Uncontrolled arrhythmia causing symptoms or hemodynamic compromise; * Recurrent syncope * Active endocarditis * Acute myocarditis or pericarditis * Symptomatic severe aortic stenosis * Uncontrolled heart failure * Acute pulmonary embolus or pulmonary infarction within 3 months of any planned study procedures; * Thrombosis of lower extremities * Suspected dissecting aneurysm * Uncontrolled asthma * Pulmonary edema * Respiratory failure * Acute non-cardiopulmonary disorders that may affect exercise performance or be aggravated by exercise (i.e., infection, renal failure, thyrotoxicosis) or * Room air desaturation at rest ≤ 85% * Mental impairment leading to inability to cooperate. * Any other condition or intercurrent illness that, in the opinion of the investigator, makes the participant a poor candidate for the trial