Physical activity (PA) has a demonstrated role in three types of tumor cancer: Sedentary behavior; breast, colon, endometrium, and a likely role in four to five other cancers with risk reduction Cancer survivors; of 25% in the most active subjects vs the least physically active. After cancer's diagnosis, there Mechanisms; is a positive association between PA and reduction in the risk of recurrence and overall and Fatigue; specific mortality in patients with non-metastatic breast, colon and prostate cancer. In cancer Physical activity survivors, post-diagnosis PA may also have beneficial effects on fatigue, quality of life, body image and self-esteem, emotional well-being, sexuality, sleep disturbance, social functioning, anxiety, and pain at varying follow-up periods. There is a growing body of research evidence that links sedentary behavior (time spent sitting) with cancer risk. These scientific data highlight the major rote of PA and limitation of sitting time both in cancer prevention but also in the management of patients during and after cancer. (C) 2020 Societe francaise de nutrition.