The aim of the study is to analyze the determinants (barriers and facilitators) of the daily physical activity level in a population of patients with cystic fibrosis. A population of patients will be included in order to realize an assessment of their daily physical activity level over an entire week. A specific questionnaire, designed from 3 different questionnaires, will be associated to the physical activity evaluation and will allow to asses psycho-social and environmental factors.

Physical activity (PA) is a major component of the management of patients with cystic fibrosis (CF). Regular PA is associated, in cystic fibrosis as in other pathologies, with health benefits and a greater life expectancy. However, the literature shows an absence of consensus for the daily PA level reached by CF patients, and also for the determinants of this PA level. It appears that CF patients tend to have a reduced PA level, compared to international guidelines. Some determinants have already been mentioned, like physical, psychological or organizational factors. But these factors have not been considered in a multifactorial way, by also considering social and environmental factors, and are rarely associated with objective PA level measurement or only reported in paediatric population. A better comprehension of these determinants of daily PA level represents an important issue for the optimization of interventions designed for the promotion of PA in cystic fibrosis.

For this study, a population of CF patients will realize an evaluation of their daily PA level based on accelerometry (by wearing a portable device over 7 days). During the PA assessment, patients will have a questionnaire to fill in, delivered with the sensor. The objective assessment of PA level will be analyzed with regard to various parameters from different dimensions: individual, clinical, psycho-social and environmental. Individual and clinical parameters will be collected from patients' data routinely assessed for the management of patients. Psycho-social and environmental parameters will be assessed with a specific questionnaire, specifically designed from 3 different questionnaires.

Inclusion Criteria:

• Diagnosis of cystic fibrosis confirmed by the identification of genetic mutation and/or positive sweat test
• regular follow-up in CF centers ;
• age higher than 6 years old
• stable clinical status, away from exacerbation period or antibiotic treatment.

Exclusion Criteria:

• transplant patient or patient waiting for a transplant
• inability to fill in the questionnaire or to complete the planned evaluations
• ongoing participation in another research protocol (interventional study)
• refusal to participate in the study
• patient under legal protection.