Study 1:

The investigator hypothesizes that the level of knowledge about the benefits of physical activity, physical activity level and physical fatigue level observed in cancer patients, would influence their beliefs about physical activity and their intention to engage in AP.

Study 2:

Because of a recent research, it is shown that a narrative message from a peer generates an identification, a sense of self-efficacy and intention to practice in sedentary patients with breast cancer.

The investigator hypothesize that a promotional message about physical activity, issued by a self-determined peer (intrinsic motivation), compared to a non-self-determined peer (extrinsic motivation), generate higher scores of positive beliefs about physical activity and intention to engage in a physical activity program for sedentary patients.

These promotional messages will be delivered through two videos, one featuring the self-determined pair, the other featuring the non-self-determined pair.

Inclusion Criteria:

• PS 0-3
• Patients with breast cancer undergoing chemotherapy treatment
• neoadjuvant, adjuvant, metastatic, any histological type, any stage breast cancer
• Sedentary Patients (physical activity score of Dijon less than or equal to 20)

Exclusion Criteria:

• Patients with PS greater than 3
• Patients with cognitive disorders not allowing them to understand the questionnaires and study procedures