Increased bronchial parasympathetic tone in elite cross-country and biathlon skiers: a randomised crossover study

Increased parasympathetic activity in endurance-trained athletes has been reported by heart rate variability and pupillometry. Our primary objective was to assess parasympathetic activity and tone in the lower respiratory tract by investigating the effect of cholinergic antagonism by inhaled ipratropium bromide compared to the β₂-receptor stimulating effect of inhaled salbutamol in elite cross-country and biathlon skiers. We also examined the medications' relationship to cholinergic sensitivity as measured by bronchial responsiveness to methacholine (PD_20met).

In a randomised crossover study, 20 cross-country and two biathlon skiers (14♂/8♀) aged 20-37 years from the Norwegian national teams measured reversibility to inhaled ipratropium bromide and inhaled salbutamol and PD_20met on three separate days. A positive reversibility test was defined as an increase in forced expiratory volume in 1 s (FEV₁) of ≥12%. Spirometry was performed before and 45 and 15 min after inhaled ipratropium bromide and inhaled salbutamol, respectively. Bronchodilating medication was withheld according to the European Respiratory Society (ERS) guidelines. Correlations were assessed by Pearson's correlation coefficient (r).

Five athletes had significant reversibility after inhaled ipratropium bromide, and none after inhaled salbutamol. Twelve athletes (54.5%) had PD_20met <8 μmol (1.57 mg). PD_20met correlated negatively with ▵FEV₁ after inhaled ipratropium bromide (r=-0.85, p<0.0001), but not after inhaled salbutamol (r=-0.308, p=0.16).

In elite skiers, cholinergic sensitivity (PD_20met) had a highly significant inverse correlation to the cholinergic antagonism of inhaled ipratropium bromide, but not at all to the bronchodilating inhaled salbutamol. This markedly increased bronchial parasympathetic tone may represent an important cholinergic role in the development of skier's asthma.