The muscles in the lungs contract and narrow and the cells lining the airways produce excessive amounts of mucus making breathing difficult. Dust, animal fur, pollen, air pollutants, tobacco smoke, cold air, or exercise can trigger an attack. It is not fully understood why, in some individuals, exercise causes an asthma attack. It has been suggested that the tissue lining the lungs is very sensitive to the cooling and drying effect of increased breathing frequency, thus causing irritation and difficulty breathing. An asthma attack may occur during the exercise session, immediately following exercise or 3-9 hours after exercise.
Attacks range in severity from light coughing to total airway obstruction.
The occurrence of an asthma attack is related to the type of exercise and the environment in which exercise takes place. Outdoor running appears to be the most asthma inducing form of exercise. Swimming rarely leads to an attack because the air above the water tends to be warmer and contain more moisture. Short-burst activities like tennis, volleyball, or strength training are also less likely to lead to an asthma attack. A scarf or facemask can be used to help trap moisture when exercising outdoors in cold weather.