Inclusion Criteria:  Adult female (aged 19 or older) First, primary diagnosis of Stage I-IIIa breast cancer Hormone receptor positive (ER+ and/or PR+) diagnosis Human epidermal growth factor receptor 2 negative (HER2-) diagnosis Completed primary adjuvant treatment (i.e., surgery, chemotherapy, and/or radiation therapy) Currently prescribed an aromatase inhibitor No evidence of possible cognitive impairment as assessed using the Mini-Mental State Exam (MMSE; score >24) Sedentary except for casual lifestyle recreation. This is defined as self-reporting 20+ minutes of exercise physical activity on 2 or fewer days per week within the previous six months. Receive physician's clearance to participate in an exercise program Agree to be randomized  Exclusion Criteria:  Males. Stage 0 breast cancer diagnosis or metastatic disease Currently receiving chemotherapy or radiation therapy for any cancer Scheduled to receive breast surgery (e.g., mastectomy, reconstructive surgery) during the study period Second cancer diagnosis (excluding non-invasive skin cancers; including breast cancer recurrence) Self-report an 20+ minutes of exercise physical activity on 3+ days per week for the previous 6 months Pregnant or plan to become pregnant during study period. Is not cleared to participate in exercise by a physician. Enrolled in another physical activity program Unable to cycle on a stationary bike Unwilling to complete study requirements History of stroke, transient ischemic attack, other neurological disorders, or brain surgery involving tissue removal Clinically significant MMSE score (<24) during baseline procedures