Reduced airway responsiveness in nonelite runners

Purpose: The effects of endurance training on airway responsiveness in nonasthmatic subjects are poorly defined. We hypothesized that airway responsiveness may differ between nonelite endurance athletes and sedentary subjects, and studied healthy, nonelite runners and sedentary controls by single-dose methacholine challenges carried out in the absence of deep inspirations, in that deep inspirations are known to oppose airway narrowing in nonasthmatic subjects. Methods: A total of 20 nonasthmatic nonelite runners (mean age ± SD: 43.0 ± 8.5 yr; training volume: 68 knrwk ^-1; range: 40-100; racing experience: 11 ± 8 yr) and 20 sedentary controls (age: 44.0 ± 20.6 yr) were studied, all of them being normoreactive to standard methacholine challenge up to 25 mg·mL ^-1 concentration. All subjects were studied at rest; six runners were also studied about 1 h after completing the Palermo marathon (December 8, 2001). The primary outcome of the study was the inspiratory vital capacity (IVC) obtained after single-dose methacholine inhalation at the end of 20 min of deep inspiration prohibition. Results: At rest, IVC decreased by 10.5 ± 8.1% after challenge with methacholine at 75 mg·mL^-1 in athletes, and by 24.3 ± 16.1% after a methacholine concentration of 52 ± 5.7 mg·mL^-1 in sedentary controls (P = 0.002). The decreased response to methacholine in runners did not correlate with static lung volumes, amount of weekly training, or running experience. Conclusion: Methacholine challenge under deep inspiration prohibition revealed that endurance training attenuates airway responsiveness in nonasthmatic, nonelite runners. Airway hyporesponsiveness was potentiated after the marathon, suggesting involvement of humoral (i.e., catecholamine levels), airway factors (i.e., nitric oxide), or both in modulating airway tone after exercise.