title: Influence of sympatho-vagal balance on airway responsiveness in athletes.
abstract: The increased prevalence of airway hyperresponsiveness (AHR) observed among athletes suggests that high-level training may contribute to the development of AHR. We investigated the possible influence of the sympatho-vagal balance on this phenomenon in 40 athletes and 10 sedentary controls. Each subject filled out a respiratory questionnaire, had a methacholine challenge, and measurements were made of their baseline plasma catecholamines [epinephrine (E), norepinephrine (NE) and dopamine (DA)] as a reflection of sympathetic tone, and their heart rate variability (SDNN: standard deviation of all normal-to-normal intervals) as an indicator of parasympathetic tone. The athletes had a 45% prevalence of AHR (defined as PC20 < 16 mg/ml, where PC20 is the concentration of methacholine inducing a 20% fall in the forced expiratory volume in 1 s, FEV1) with a mean PC20 of 21.2 mg/ml compared with 10% prevalence (mean PC20: 74.4 mg/ml) in sedentary subjects (P < 0.01). Plasma catecholamine values were not significantly different between the two groups (all P > 0.05), but the estimated parasympathetic tone was higher in athletes (P = 0.01). When data from all subjects were analyzed together, plasma E and NE correlated with PC20 (r = 0.39, P = 0.005 and r = 0.29, P < 0.005) but DA and SDNN did not (both P > 0.05). However, the ratios E/SDNN, NE/SDNN and DA/SDNN showed significant correlations with PC20 (r = 0.42, P < 0.01; r = 0.33, P < 0.005 and r = 0.31, P < 0.05, respectively) This study suggests that the sympatho-vagal balance may contribute to the increased AHR in the population studied but this influence alone cannot explain the higher prevalence of AHR in athletes.
authors.affiliation: Centre de Recherche de l'H pital Laval, Institut Universitaire de Cardiologie et de Pneumologie, Université Laval, Sainte-Foy, Québec, Canada. lpboulet@med.ulaval.ca
authors.forename: J B
authors.initials: JB
authors.lastname: Langdeau
authors.forename: H
authors.initials: H
authors.lastname: Turcotte
authors.forename: P
authors.initials: P
authors.lastname: Desagné
authors.forename: J
authors.initials: J
authors.lastname: Jobin
authors.forename: L P
authors.initials: LP
authors.lastname: Boulet
mesh_terms: D000328:Adult; D016535:Bronchial Hyperreactivity / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D002395:Catecholamines / Q000097:blood; D005260:Female; D005541:Forced Expiratory Volume; D006339:Heart Rate; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D013177:Sports; D013564:Sympathetic Nervous System / Q000378:metabolism*; D014630:Vagus Nerve / Q000503:physiopathology*
chemical_list: D002395:Catecholamines; D016210:Methacholine Chloride