Airway reactivity and exercise in healthy subjects.

The interaction of exercise, methacholine challenge, and beta-adrenergic blockade was investigated in eight healthy subjects. We measured the response to increasing doses of aerosolized methacholine, examining maximum expiratory flow rates. These responses were compared with those obtained on separate days when each methacholine challenge followed submaximal exercise or submaximal exercise in the presence of Beta-blockade. The possible independent effect of increased ventilation (20 +/- 6.7 L/min) was also studied during methacholine challenge. Methacholine-induced bronchospasm was not augmented by exercise alone or by exercise in the presence of beta-blockade, nor was this response significantly altered by hyperventilation during methacholine aerosol challenge. These findings suggest that airway hyperreactivity cannot be induced in healthy subjects by levels of exercise that commonly provoke exercise-induced bronchospasm in asthmatic patients.