Exercise-induced asthma happens when the airways narrow during or after exercise.1 Exercise is a common trigger for people with underlying asthma. However, about 20% of recreational exercisers have asthma only related to exercise.2 The proportion of athletes with exercise-induced asthma may be even higher than that.1 Long-distance endurance athletes, such as cyclists, swimmers, or runners, are most likely to have asthma.3
The symptoms of exercise-induced asthma vary from person to person. A person may have some or all of the typical asthma symptoms: coughing, wheezing, chest tightness, or shortness of breath. The symptoms are usually mild to moderate. They may be severe enough to impair athletic performance, but do not usually cause serious trouble breathing.1
Another term for exercise-induced asthma is “exercise-induced bronchoconstriction.”
What causes exercise-induced asthma?
Cold, dry air: Exercise-induced asthma is common in ice-rink athletes and cross-country skiers.1 During exercise in cold, dry air, the lungs lose water, heat, or both.4 In a person with exercise-induced asthma, these losses cause the airways to narrow. This form of exercise-induced asthma has been called cross-country skiers’ asthma.5 Having a mild cold during strenuous, cold weather exercise may contribute to asthma symptoms. This type of asthma seems to be non-allergic, but people with cross-country skiers’ asthma do have airway inflammation.
Indoor pool air: The humid, warm air of the pool should protect against the loss of heat and water. However, as many as 79% of competitive swimmers have exercise-induced asthma or hyperactive airways.3 One theory is that breathing in chlorine byproducts for years leads to airway inflammation and structural changes.6
Ozone and allergens: Many distance runners also have exercise-induced asthma. Exercising in environments with high levels of ozone and allergens may trigger asthma for these athletes.1
How does exercise lead to asthma symptoms?
The symptoms usually start during or after vigorous activity. Rapid, deep breathing causes the airways to narrow. In some—but not all—people with exercise-induced asthma, exercise triggers an inflammatory reaction.1,4
Symptoms are the worst five to ten minutes after stopping exercise, and they are usually gone 20 to 30 minutes later.4
How is exercise-induced asthma diagnosed?
Asthma symptoms such as shortness of breath, cough, wheeze, and mucus production, are also associated with hard exercise. An exercise challenge and lung function test are needed to diagnose exercise-induced asthma.1
The exercise challenge can be done in many settings: laboratory, free run, or after the activity that caused symptoms previously.4 The goal is to get your heart rate up to about 80% of your maximum for four to six minutes.4 Heart rate is used to estimate exercise intensity.1 Some laboratories use more precise ways to measure exercise intensity by how hard you breathe.
Spirometry is the preferred lung function test for exercise-induced asthma.1 You may be asked to perform this test before exercising, and then every five minutes after exercising for 20 to 30 minutes.4 Spirometry measures how much air you can exhale in one second (called FEV1). If FEV1 decreases by 10% or more after exercising, you may have exercise-induced asthma.1
An alternative to spirometry is measuring peak expiratory flow before and after an exercise challenge. This test is less reliable.1 However, a peak flow meter is portable and can be used in the environment that caused asthma symptoms.7 Newer peak flow meters may also be able to measure FEV1.
If an exercise challenge is not possible, you may be asked to do an “indirect” challenge.1 These involve inhaling mixtures that simulate exercise conditions. Two common tests are called:
- Eucapnic voluntary hyperpnea challenge
- Mannitol challenge
What can I do to reduce my symptoms?
For some athletes, a ten-minute warm-up can reduce exercise-induced asthma for about two hours.1 The best warm-ups include high-intensity intervals.
For people with cross-country skiers’ asthma, breathing through a face mask warms and humidifies the air. The warm, humid air is easier to breath.1
Diets for exercise-induced asthma have not been well studied. There is some evidence that a low-salt diet may help.1 Vitamin C supplement or a fish oil supplement might also be helpful. In two studies of vitamin C and one study of fish oil, people who took the supplement had less airway narrowing than people who did not take the supplement.
What medications are used to treat exercise-induced asthma?
The goal of asthma treatment is that you can participate fully in any activity you choose.4 If you have underlying asthma outside of exercise, a long-term control medication may be needed. This medication reduces inflammation and airway sensitivity.
Your health care provider may suggest taking a medication before you begin exercise. Short-acting beta-agonists (SABAs) are often recommended for exercise-induced asthma.1 These medications relax the airway and allow it to open up. They are taken five to 20 minutes before starting to exercise. They are effective for two to four hours.
If you are using a SABA every day, your provider may recommend adding another medication.1 Your provider may prescribe a daily inhaled corticosteroid or leukotriene receptor antagonist.1 For athletes with allergies, an antihistamine may be recommended.1