Although the exact physiologic mechanism by which exercise improves clearing of airways secretions in CF is not entirely clear, possible explanations are attributed to increased airflow and mechanical clearing of mucus. Following physical exertion there is an increase in tidal volume and respiratory flow to meet tissue demands. Increasing peak expiratory flow (PEF) to peak inspiratory flow (PIF) ratio may help drive the mucus past the oropharynx to clear more easily. Additional benefits of exercise in patients with CF are similar to the healthy population and includes overall improvement in cardiovascular health, musculoskeletal health, and quality of life. Maximal oxygen consumption (VO2peak) serves as a strong prognosis marker associated with an approximate 8-year survival in CF patients and correlates with the number of hospital admissions due to respiratory exacerbations. There is paucity of data regarding exercise capacity in non-CF bronchiectasis.