Effect of endurance exercise on respiratory muscle function in patients with cystic fibrosis

► Whether patients with cystic fibrosis (CF) develop low frequency fatigue (LFF) of the respiratory muscles following exercise is unknown. ► Dynamic hyperinflation (DH) occurs during exercise in patients with CF. ► DH imposes both elastic and threshold loads on the inspiratory muscles and places them at a mechanical disadvantage due to muscle shortening. ► DH imposes a progressively resistive load and lengthens the expiratory muscles, increasing their susceptibility to develop LFF. ► Despite the high intensity of the exercise performed, none of the CF patients displayed evidence of LFF of the respiratory muscles post exercise.