High-Intensity Interval Training for Stage I-III Breast Cancer Patients

PRIMARY OBJECTIVES: I. To assess the feasibility (completion of \> 80% exercise sessions) of utilizing high-intensity interval training (HIT). II. To determine the effects of HIT on aerobic exercise adaptation when compared to delayed group. III. To examine the effects of HIT on left ventricular function when compared to delayed group. IV. To determine the effects of HIT on endothelial function, arterial stiffness, and vascular atherosclerosis when compared to delayed group. OUTLINE: Participants are randomized to 1 of 2 groups. ARM I: HIT (High-intensity Interval Training) group - Participants undergo HIT over 30 minutes, thrice weekly for 8 weeks. ARM II: DEL (Delayed/usual care) group - Participants maintain their current sedentary activity level (\< 60 minutes of total exercise per week) for 8 weeks. Participants document their weekly activity in an exercise log. Following completion of all study visits, participants are given the option to complete the HIT exercise program as in Arm I. After completion of study, patients are followed up at weeks 9 and 17.