Methacholine Airway Responsiveness Decreases during Exercise in Asthmatic Subjects

In many asthmatic subjects, bronchoconstriction develops 2 to 5 min after exercise, reaches a maximum at approximately 10 min, and declines over the next 60 min. However, bronchodilation is typically observed during and immediately after exercise. We measured the bronchoconstrictor responses to increasing concentrations of inhaled methacholine at rest and during two levels of exercise in seven asthmatic subjects to determine the protection …