Background: Whereas a high prevalence of bronchial abnormalities has been reported in endurance athletes, its underlying mechanisms and consequences during exercise are still unclear.
Study objectives: The purpose of this study was to assess the following: (1) bronchial responsiveness to methacholine and to exercise; (2) airway inflammation; and (3) airflow limitation during intense exercise in endurance athletes with respiratory symptoms.
Design: Cross-sectional observational study.
Setting: Lung function and exercise laboratory at a university hospital.
Patients and measurements: Thirty-nine endurance athletes and 13 sedentary control subjects were explored for the following: (1) self-reported respiratory symptoms; (2) bronchial hyperresponsiveness (BHR) to methacholine and exercise; (3) airflow limitation during intense exercise; and (4) bronchial inflammation using induced sputum and nitric oxide (NO) exhalation.
Results: Fifteen athletes (38%) showed BHR to methacholine and/or exercise in association with bronchial eosinophilia (mean [± SD] eosinophil count, 4.1 ± 8.5% vs 0.3 ± 0.9% vs 0%, respectively), higher NO concentrations (19 ± 10 vs 14 ± 4 vs 13 ± 4 parts per billion, respectively), a higher prevalence of atopy, and more exercise-induced symptoms compared with nonhyperresponsive athletes and control subjects (p < 0.05). Furthermore, airflow limitation during intense exercise was observed in eight athletes, among whom five had BHR. Athletes with airflow limitation reported more symptoms and had FEV1, FEV1/FVC ratio, and forced expiratory flow at midexpiratory phase values of 14%, 9%, and 29%, respectively, lower compared with those of nonlimited athletes (p < 0.05).
Conclusion: BHR in endurance athletes was associated with the criteria of eosinophilic airway inflammation and atopy, whereas airflow limitation during exercise was primarily a consequence of decreased resting spirometric values. Both BHR and bronchial obstruction at rest with subsequent expiratory flow limitation during exercise may promote respiratory symptoms during exercise in athletes.