Brief Summary: Rationale: Exercise therapy may improve the quality of life of breast cancer survivors. Purpose: This randomized clinical trial studies exercise therapy and quality of life in postmenopausal early breast cancer survivors receiving aromatase inhibitor therapy.

Detailed Description: PRIMARY OBJECTIVES: I. To determine whether a 16-week exercise intervention will improve components of metastasis (MetS) in breast cancer survivors soon after completion of cancer-related treatments by measuring changes in body composition, waist circumference, blood pressure, and serum levels of insulin, glucose, lipids, C-reactive protein, and hemoglobin A1c (HbA1c). II. To determine whether a 16-week exercise intervention will improve physical fitness in breast cancer survivors soon after completion of cancer-related treatments by measuring cardiorespiratory fitness and muscle strength. III. To assesses the feasibility of a supervised exercise intervention in early breast cancer survivors. IV. To determine whether a 16-week exercise intervention will result in a reduction in adipose tissue inflammation in obese breast cancer survivors soon after completion of cancer-related treatments by measuring ATM phenotype and ATM cytokine expression. V. To determine whether breast cancer survivors can maintain positive benefits of an exercise intervention following a 12-week follow-up period by measuring changes in body composition, waist circumference, blood pressure, and serum levels of insulin, glucose, lipids, C-reactive protein, and HbA1c, cardiorespiratory fitness and muscle strength. OUTLINE: Patients are randomized to 1 of 2 arms. Arm I (Control): Patients refrain from increasing physical activity levels for 16 weeks. Arm II (Exercise): Patients participate in supervised exercise sessions over 60 minutes thrice weekly and are encouraged to participate in a home-based exercise session over 30-45 minutes once weekly for 16 weeks.