The physiological mechanisms by which exercise may clear secretions in subjects with cystic fibrosis (CF) are unknown. The purpose of this study was to compare ventilation, respiratory flow and sputum properties following treadmill and cycle exercise to resting breathing (control). In 14 adult subjects with CF, ventilation and respiratory flow were measured during 20 minutes of resting breathing, treadmill and cycle exercise in a three-day, cross-over study. Treadmill and cycle exercise were performed at the workrate equivalent to 60% of the subject’s peak VO(2). Ease of expectoration and sputum properties (solids content and mechanical impedance) were measured before and immediately after the interventions and after 20 minutes recovery. Ease of expectoration improved following exercise. Ventilation and respiratory flow were significantly higher during treadmill and cycle exercise, compared to control. Sputum solids content did not change following treadmill or cycle exercise. There was a significantly greater decrease in sputum mechanical impedance following treadmill exercise compared to control, but no significant decrease in sputum mechanical impedance following cycle exercise compared to control.
The improvement in ease of expectoration following exercise may have been due to the higher ventilation and respiratory flow. The reductions in sputum mechanical impedance with treadmill exercise may have been due to the trunk oscillations associated with walking.