Cancer-related fatigue (CRF) is a complex multi-dimensional construct related to reduced physical function and health-related quality of life. This symptom is under-reported by patients and and undertreated by clinicians. Recent reviews have concluded that exercise reduces cancer-related fatigue. The NCCN recommends that all cancer patients should be screened for fatigue regularly. As management of CRF is currently suboptimal, a change of approach is required. Breast cancer survivors who had finished their treatments in the last 6 months, did not have any evidence of disease and were able to manage the accelerometer were offered to participate in a cross sectional study. CRF was evaluated through PERFORM, a questionnaire developed and validated in Spanish speakers.