The proposed study compares the outcomes of a physical activity intervention begun at diagnosis, continuing through active cancer treatment and into six months of survivorship compared to the outcomes of a control group receiving limited information on activity.

Patients (with stage 0 to stage III breast cancer)receiving chemotherapy, radiation or both chemotherapy and radiation will be included in the study.Randomization will be stratified by disease stage at diagnosis, treatment modalities planned, and hormonal status. Each patient will have a weekly goal of 2000 calories burned and 18 MET-hours of exercise which can be achieved in 4 to 7 hours of physical activity per week. Resistance training, using weight machines and aerobic training using treadmills, elliptical trainers and stationary bicycles, will be utilized in the intervention group. The control group will receive basic information on physical activity but not be instructed. Any physical activity in this group will be self-reported. Change in C-reactive protein will be the primary endpoint. Changes in other laboratory values, DEXA measurements, and quality of life measurements will be secondary endpoints.

Inclusion Criteria:

1. Consent to participate in study
2. Women aged 18 and older
3. Stage 0 to III breast cancer prior to any treatment and at time of diagnosis
4. Requires treatment that includes chemotherapy, radiation therapy or both chemotherapy and radiation therapy
5. Adequate fitness to participate in a physical activity as assessed by the investigator
6. Willing and able to participate in a prescribed exercise program

Exclusion Criteria:

1. Metastatic breast cancer (Stage IV)
2. Initiation of treatment regimen prior to enrollment
3. Treatment for breast cancer not requiring chemotherapy or radiation therapy
4. Patients who are pregnant (negative urine pregnancy test required at baseline to determine eligibility in women of child bearing potential).
5. Currently lactating
6. Do not read, understand, or speak English

Eligible participants will not be included if they have:

1. known cardiac disease,
2. uncontrolled hypertension,
3. uncontrolled thyroid disease,
4. diabetes mellitus,
5. mental illness,
6. infection,
7. immune or endocrine abnormality,
8. body weight reduction I10% in past 6 months, and
9. positive exercise stress test.
10. Major surgery within last 6 months that requires exercise restriction