Utilizing Exhaled Breathe Condensate Collection to Study Ion Regulation in Cystic Fibrosis

Inclusion Criteria: Healthy subjects: * no cardiovascular abnormalities * not overweight BMI\>25 * 18-55 years of age CF subjects: * mild to moderate CF (FEV1\>40% predicted) * clinically diagnosed with positive sweat test (sweat Cl-\>60mmol/L) * 10-55 years of age * clinically stable Exclusion Criteria: Healthy subjects will be excluded if: * If unable to consent for him/herself (cognitive impairment) * Have a history or evidence of cardiovascular and/or pulmonary abnormalities. * Have an abnormal 12-lead EKG * Have an abnormal pulmonary function test * Have a history of asthma * Have a history of renal disease or estimated creatinine clearance \< 55ml/min * Women who are pregnant or planning to become pregnant during the study CF subjects: * If unable to consent for him/herself (cognitive impairment) * Physically unable to perform exercise or breathing tests * Have a history of renal disease or estimated creatinine clearance \< 55ml/min * Women who are pregnant or planning to become pregnant during the study. * Have an abnormal 12-lead EKG * Cystic Fibrosis related diabetes is uncontrolled * Forced Expiratory Volume after 1 second (FEV1) is less than 40% predicted * Have a history of joint disease * Have history of pulmonary exacerbation within the last two weeks * Experienced pulmonary hemorrhage within 6 months resulting in greater than 50cc of blood in the sputum * not currently enrolled in any other research study