Mechanisms of asthma development in elite athletes

Exercise-induced bronchoconstriction is caused by heat loss and water loss through respiration during exercise, leading to mediator release in the airways and to increased parasympathetic nervous activity in the airways, thereby causing constriction of bronchial smooth muscle and increased bronchial secretions as well as vasodilation in the bronchial vessels. Development of asthma and bronchial hyperresponsiveness in the competing elite athlete is presently considered to be caused by the frequently repeated increased ventilation occurring during training and competitions. Usually, the endurance athlete is at risk; and the risk is increased by repeated exposure to environmental factors such as cold air (cross-country skiers and other winter athletes), organic chlorine compounds (swimmers and other water athletes), pollution (long-distance runners and cyclists) to name a few.