Cystic fibrosis is a multisystem genetic disease whose severity, linked to the nature of the mutation in the gene carried, is linked to respiratory impairment, which determines the vital prognosis. Considerable progress has been made in the management of this disease, amplified in recent years by the arrival of CFTR (cystic fibrosis transmembrane conductance regulator) modulator drugs, and in particular the triple treatment combination of elexacaftor-tezacaftor-ivacaftor (ETI). This modulator therapy improves clinical condition, particularly respiratory, and transforms quality of life and prognosis for some patients. Faced with this clinical improvement, practices and care paths are adapting. Professionals will have to cope with the emergence of new clinical conditions linked to the ageing of this at-risk population and the functional decline due to a sedentary lifestyle and age. The working hypothesis is that a better understanding of the physical activity and sedentary lifestyle profiles of the adult population with cystic fibrosis, and in particular the characterization of the profile of inactive and high sedentary patients under ETI, will enable us to identify and target patients whose lifestyle habits reflect a greater health risk, and for whom care by rehabilitators and adapted physical activity (APA) teachers and personalized advice could be put in place. The aim of this study is to characterize the physical activity and sedentary profile of adults with cystic fibrosis. ACTIVMUCO is an observational, cross-sectional, single-center study. A subgroup of adults with high sedentary and inactive under ETI will be studied more specifically by actimetry (prospective follow-up) and interview.