 Physical exercise has been identified as a major item of many chronic diseases and cancer rehabilitation. It contributes to an improvement in the quality of life and to a decrease in the current treatment side effects and mortality. Cancer in association with treatment toxicity and an inactive lifestyle lead to a fall in physical capability and causes problems in daily activities. The physical capacity and the tolerance for exercise fall simultaneously leading to a deconditioning vicious circle which increases physical, psychological and emotional symptoms of fatigue. Therefore, physical activity for health is a valid and relevant way to improve quality of life and to manage cancer patient fatigue. The aim of the study is the assessment of the effects of a physical activity retraining program on aerobic capacity, strength and fatigue, in a breast cancer population treated by adjuvant chemotherapy. 