CFTR and cystic fibrosis: The subjects had been diagnosed with cystic fibrosis in Hacettepe University Medical Faculty Department of Child Pulmonary Diseases by clinical findings consistent with cystic fibrosis and a sweat chloride value above 60 mEq/L on two measurements or cystic fibrosis-relevant mutations on both alleles of the CFTR gene, an age of ≥ 13, a forced expiratory volume in 1s (FEV1) of ≥ 35%, and the ability to perform physical activity.