The purpose of this study is to conduct a 12-month randomized controlled trial comparing the effects of strength training exercise to stretching and relaxation exercise (control) on body composition (bone, muscle and fat mass), energy balance, bone turnover, and physical function (strength, power, gait, balance and self-report physical function and symptoms) in women who experienced premature menopause from chemotherapy for breast cancer.

As a result of treatment, breast cancer survivors typically experience unhealthy changes in body composition (bone, muscle and fat). Treatments disrupt normal bone and energy balance resulting in bone and muscle wasting and fat gain. Premenopausal women are at greatest risk for these declines because most are thrust into early menopause from chemotherapy. Hormone manipulation therapy (i.e., tamoxifen or arimidex) may further affect these tissues. Exercise can prevent bone and muscle loss and promote fat loss. However, the ability of exercise to reverse unfavorable changes in all components of body composition in women experiencing early menopause from breast cancer treatment has not been specifically studied.

Inclusion Criteria:

• Diagnosed breast cancer stage I-IIIa
• Completion of a chemotherapy regimen within the previous 5 years
• Premenopausal status (9-12 menstrual cycles/year) at the initiation of chemotherapy
• Complete absence of menstrual cycles for at least 6 months and within one year after starting chemotherapy OR confirmed menopause by blood tests conducted in the last 12 months prior to enrollment.

Exclusion Criteria:

• Presence of any known metastases
• Clinically defined osteoporosis
• Current or previous use of medications known to affect bone metabolism
• Current regular participation (>2x/wk for at least 30 min/session) in planned impact activities (i.e., volleyball, basketball), or resistance training
• A medical condition, disorder, or medication that contraindicates participation in moderate intensity impact or resistance exercise