The exact cause of exercise-induced asthma is not clear. But exercise-induced asthma, which also may be referred to as exercise-induced bronchospasms or exercise-induced bronchoconstriction, appears to be related to strenuous or continuous exercise or physical exertion — oftentimes performed in cool, dry weather.
Ninety percent of children with chronic asthma are likely to encounter symptoms when exercising. However, other children without chronic asthma appear to develop symptoms only when they exercise. Forty percent of those children may have allergic rhinitis, but 9 percent with exercise-induced asthma have no history of allergy or asthma at all.
The symptoms of exercise-induced asthma usually will begin within five to ten minutes after beginning to exercise, or within five to ten minutes after a brief exercise period has stopped. After about twenty to thirty minutes, your child will begin to feel better.
Children with exercise-induced asthma are sensitive to sudden changes in temperature and humidity. The symptoms often appear worse with cold and dry air rather than with warm, humid air.
Why does cooler air trigger breathing problems during exercise?
A child — while exercising — breathes faster and harder through her mouth so she can pull more air into her lungs. But the air that comes through her mouth has not been filtered, warmed, or humidified through her nose. This means the air that she breathes is cooler and drier than normal.
With mouth breathing, air is moistened to about 60 to 70 percent relative humidity, while nose-breathing warms and saturates air to about 80 to 90 percent humidity before reaching the lungs. For the child with asthma, her extra-sensitive airways react to the cooler air, with muscle bands around the airways contracting. This narrows the airways, making it more difficult to breathe, resulting in symptoms that can include:
Tightening of the chest
Unusual fatigue while exercising
Prolonged shortness of breath when exercising
With children, who may not know how to recognize exercise-induced asthma, their symptoms might be somewhat harder to detect. For instance, they may complain to you about: chest congestion, discomfort, or pain; a sensitivity to cold air that is accompanied by coughing when moving from outdoors to indoors; a general feeling of being out of shape or winded; comments about tiring easily or low energy; dizziness; frequent colds; stomach aches; frequent throat clearing; and observations that they can't keep up with their friends when running or playing.
Parents concerned about these symptoms should ask their health care provider about what treatments are available.
Warmer outside air, however, may not always protect against exercise-induced asthma. Pollens and molds are present when children play and exercise outside during warmer weather, especially in the late summer. During extended dry periods or drought, these pollens and molds could dramatically escalate and increase the chance that your child could experience breathing difficulties while exercising.
Diagnosis of Exercise-Induced Asthma
While the symptoms exhibited by a child during exercise may point to exercise-induced asthma, the condition should be diagnosed by a health care provider. This diagnosis will be based on medical history, a physical exam, a simple lung function test, and response to treatment. However, diagnosing this condition is not always simple.
When the diagnosis is unclear, a medical professional can confirm it through an in-office visit by using breathing tests at rest and after exercise, for instance, using a treadmill or cycle for about six to eight minutes. Both before and several times after the test, the child breathes into a spirometer, a type of breathing machine that measures the ability to breathe out. A decrease of about 12 to 15 percent of the volume of air blown out could indicate possible exercise-induced asthma.
A test also can be conducted on the field following a six- to eight-minute “free run” or after participation in a sport or activity that appears related to respiratory symptoms. Again, airflow is measured before and after exercise ends. While a portable spirometer can be used, a peak flow meter can be tried as well to measure a decrease in airflow.
It is important to correctly diagnose exercise-induced asthma among children because in some cases it might be another medical condition that requires a different medical treatment.
Researchers have found that what was thought to be exercise-induced asthma in children may have causes other than asthma. While asthma is the top cause of exercise-induced asthma, some children without other asthma symptoms had other conditions such as poor physical conditioning, cardiac disease, or muscle disorders.
Another condition is vocal cord dysfunction (VCD), a disorder in which vocal cords do not open as fully as they should when breathing. Sometimes VCD and asthma may co-exist in athletes. The results need to be confirmed through further workups and testing.
If exercise-induced asthma is misdiagnosed, the child will find that a prescribed routine treatment — such as use of a short-acting inhaler before exercise — does not provide benefits that she wants during exercise. This could mean frustration for you and your child in terms of getting the proper treatment, along with use of unnecessary medication.