Effects of exercise training on airway closure in asthmatics.

We previously reported that responsiveness to methacholine (Mch) in the absence of deep inspiration (DI) decreased in healthy subjects after a short course of exercise training. We assessed whether a similar beneficial effect of exercise on airway responsiveness could occur in asthmatics. Nine patients (M/F: 3/6; mean age±SD: 24±2 yrs) with mild untreated asthma (FEV1: 100±7.4% pred, FEV1/VC 90±6.5%) underwent a series of single dose Mch bronchoprovocations in the absence of DI in the course of a 10 week training rowing program (6 hours/week of submaximal and maximal exercise), at baseline (week 0) and at weeks 5 and 10. The single dose Mch was established as the dose able to induce at least 15% reduction in IVC, and was administered to each subject at every challenge occasion. Five asthmatics (M/F: 1/4; mean age±SD: 26±3 yrs) with similar baseline lung function (FEV1: 102±7.0% pred, and FEV1/VC: 83±6.0%; p=0.57 and p=0.06, respectively) not participating in the exercise training program, served as controls. In the trained group, the Mch-induced reduction in IVC from baseline was 22±10% at week 0, 13±11% at week 5 (p=0.03), 11±8% at week 10 (p=0.028). The Mch-induced reduction in FEV1 did not change with exercise (p=0.69). The reduction in responsiveness induced by exercise was of the same magnitude of that previously obtained in healthy subjects (50% with respect to pre-training). Conversely, Mch-induced reduction in IVC in controls remained unchanged after 10 weeks (% reduction IVC at baseline: 21±20%; after 10 weeks: 29±14%, p= 0.28). This study indicates that a short course of physical training is capable of reducing airway responsiveness in mild asthmatics.