From weekend warriors to superstars, all types of athletes experience
exercise-induced asthma. They include world-class competitors like NFL
star Jerome "The Bus" Bettis and six-time Olympic gold medalist swimmer
Amy Van Dyken.
But just what is exercise-induced asthma, why does it happen, and how can it
WebMD consulted the experts to find out the answers to these questions, as
well as tips for controlling symptoms of exercise-induced asthma --
whether you're a casual athlete or a superstar.
What is Exercise-Induced Asthma?
Even many people who never experience asthma symptoms at other times have
exercise-induced asthma, experts say.
"Exercise-induced asthma occurs in almost everyone who has chronic
asthma, but there is a separate group of people who have what we call
exercise-induced bronchospasm," says Timothy J. Craig, MD, chair of the
American Academy of Allergy, Asthma and Immunology's Sports Medicine
These people, explains Craig, don't have what is considered "true"
asthma. They don't have inflammation in their lungs. Nor do they experience
symptoms when exposed to common triggers, like animals, pollen or mold.
"So unlike most people who have asthma and get exercise-induced
symptoms, these individuals don't have true asthma, but when they exercise,
they experience the symptoms of asthma," Craig tells WebMD.
Exercise-induced asthma, experienced by up to 13% of the U.S. population,
occurs when the airways narrow, making breathing difficult. Why some athletes
have exercise-induced asthma and others don't isn't entirely clear.
"The causes vary, but are usually associated with loss of heat or water,
or both, from the lungs during exercise, because of the increased ventilation
of dry and cool air," says Michael G. Miller, EdD, a spokesperson for the
National Athletic Trainers Association.
People with exercise-induced asthma have airways that are overly sensitive
to sudden changes in temperature and humidity, especially when breathing
colder, drier air, according to the American Academy of Allergy, Asthma and
During strenuous activity, people tend to breathe through their mouths.
Mouth breathing allows cold, dry air directly into the lungs, without benefit
of the warmth and moisture that nose breathing supplies. As a result, air is
moistened to only 60-70% relative humidity. Nose-breathing, meanwhile, warms
and saturates air to about 80 to 90% humidity.
The symptoms of exercise-induced asthma are similar to those of chronic
asthma, explains Miller. They include: