This is a randomised double-blind placebo-controlled crossover study. Design: 5 visits; V1: screening, familiarization, incremental cardiopulmonary exercise testing (CPET); V2: constant work-rate (CWR-CPET); V3, V4 and V5: CWR-CPET after intervention, in a random order: Placebo (P), Ipratropium Bromide (IB), Ipratropium Bromide + Salbutamol (IB+SALB).