Exercise-induced asthma: Asthma triggered by vigorous physical activity. It primarily affects children and young adults because of their high levels of physical activity, but it can occur at any age. Exercise-induced asthma is initiated by the fall in airway temperature during rapid breathing followed by rapid reheating with lowered ventilation. The more heat that is transferred, the cooler the airways become, and the more rapidly the airways rewarm, the more the bronchi are narrowed. Acute attacks can be minimized by warming up before strenuous activity. An inhalator may also be used before exertion. Also known as exercise-induced bronchospasm and thermally induced asthma.