Exercised-induced asthma is a narrowing of the airways in the lungs that is triggered by strenuous exercise. It causes shortness of breath, wheezing, coughing and other symptoms during or after exercise.
The preferred term for this condition is exercise-induced bronchoconstriction (brong-koh-kun-STRIK-shun). This term is more accurate because the exercise induces narrowing of airways (bronchoconstriction) but is not the root cause of asthma. Among people with asthma, exercise is likely just one of several factors that can induce breathing difficulties.
For most people with exercise-induced bronchoconstriction, treatment with common asthma medications and preventive measures enable them to exercise and remain active.
Signs and symptoms of exercise-induced bronchoconstriction may begin during or a few minutes after exercise, and they may persist for 30 minutes or longer if left untreated. The signs and symptoms may include:
Shortness of breath
Chest tightness or pain
Fatigue during exercise
Poorer than expected athletic performance
Feeling out of shape even when you're in good physical shape
Avoidance of activity (a sign primarily among young children)
When to see a doctor
See your doctor if you experience any signs or symptoms of exercise-induced bronchoconstriction. Because a number of conditions can cause similar symptoms, it's important to get a prompt and accurate diagnosis.
Get emergency medical treatment if you have worsening symptoms:
Shortness of breath or wheezing that is quickly getting worse
No improvement even after using a prescription inhaler for asthma attacks
Medical researchers are exploring several ideas regarding the cause of exercise-induced bronchoconstriction. There may be more than one biological process that can lead to the condition. Researchers do know that in people who experience exercise-induced bronchoconstriction, strenuous exercise sets in motion molecular events that result in inflammation and the production of mucus in the airways.
Factors that may increase the risk of the condition or act as triggers include:
High pollen counts
Chlorine in swimming pools
Chemicals used with ice rink resurfacing equipment
Respiratory infections or other lung disease
Activities with extended periods of deep breathing, such as long-distance running, swimming or soccer
Exercise-induced bronchoconstriction that is not treated can result in:
A lack of beneficial exercise
Poor performance in activities you would otherwise enjoy
Serious or life-threatening breathing difficulties, particularly among people with poorly managed asthma
In addition to asking questions about your symptoms, your doctor will conduct a medical exam. He or she will also order tests to assess your lung function and rule out other conditions that may be causing your symptoms.
Test of normal lung function
Your doctor will likely administer a spirometry (spy-ROM-uh-tree) test to assess how well your lungs function when you aren't exercising. A spirometer measures how much air you inhale, how much you exhale and how quickly you exhale.
After you do the test, your doctor may give you an inhaled medication to open your lungs (bronchodilator). You'll repeat the test, and your doctor will compare the results of the two measurements to see whether the bronchodilator improved your airflow. This initial lung function test is important for ruling out underlying chronic asthma as the cause of symptoms.
Exercise challenge tests
An additional test that enables your doctor to observe and assess symptoms is an exercise challenge. You will run on a treadmill or use other stationary exercise equipment that increases your breathing rate. This exercise needs to be intense enough to trigger the symptoms you've experienced. If needed, you might be asked to perform a real-life exercise challenge, such as climbing stairs.
Spirometry tests before and after the challenge can provide evidence of exercise-induced bronchoconstriction.
Alternate challenge tests
As an alternative to the exercise challenge, your doctor may use an inhalation test that simulates the conditions that would likely trigger exercise-induced bronchoconstriction. If your airways respond to these stimuli, then the test should produce virtually the same lung function you have when exercising.
Again spirometry tests before and after the challenge test provide information about changes in lung function. These challenge tests include the following:
Methacholine challenge, the use of an inhaled agent that interacts with certain smooth muscle cells in airways and results in bronchoconstriction
Eucapnic voluntary hyperventilation (EVH) challenge, inhaling a mixture of dry air composed of oxygen, carbon dioxide and nitrogen that simulates the exchange of air when breathing is difficult
Mannitol challenge, inhaling a dry powder that can trigger water loss on the surface of the airways and switch on molecular activity that controls inflammation — conditions that cause bronchoconstriction in people with oversensitive airways
Ruling out other conditions
Your doctor may order additional tests to rule out other conditions with symptoms similar to those of exercise-induced bronchoconstriction. These conditions include:
Vocal cord dysfunction
Irregular heartbeats (arrhythmia) or other heart conditions
Your doctor may prescribe drugs to take shortly before exercise or to take daily for long-term control.
Your doctor may prescribe a drug that you take before exercise to minimize or prevent exercise-induced bronchoconstriction. Talk to your doctor about how much time you need between taking the drug and exercising. Drugs in this group include the following:
Short-acting beta agonists (SABAs) are inhaled drugs that help open airways. These are the most commonly used and generally most effective pre-exercise medications. Daily use of a SABA is not recommended, however, because you may develop a tolerance to its effect. These drugs include albuterol (ProAir HFA, Proventil HFA, Ventolin HFA), levalbuterol (Xopenex HFA) and pirbuterol (Maxair).
Ipratropium (Atrovent HFA) is an inhaled medication that relaxes the airways and may be effective for some people. A generic version of ipratropium also can be taken with a nebulizer.
Long-term control medications
Your doctor may prescribe a long-term control drug in addition to daily use of a pre-exercise medication, to manage underlying chronic asthma or to manage symptoms when pre-exercise treatment alone isn't effective. These medications, usually taken daily, include the following:
Inhaled corticosteroids help suppress inflammation in your airways. You may need to take the drug two to four weeks before they will have maximum benefit. These medications include fluticasone (Flovent Diskus, Flovent HFA), budesonide (Pulmicort Flexhaler), mometasone (Asmanex Twisthaler) and beclomethasone (Qvar).
Combination inhalers contain a corticosteroid and a long-acting beta agonist (LABA), a drug that relaxes airways. While these inhalers are prescribed for long-term control, your doctor may recommend use prior to exercise. Combination inhalers include fluticasone and salmeterol (Advair Diskus), budesonide and formoterol (Symbicort), and mometasone and formoterol (Dulera).
Leukotriene modifiers are oral medications that may block inflammatory activity for some people. These drugs may be used daily or as a preventive treatment before exercise if taken at least two hours in advance. Examples include montelukast (Singulair), zafirlukast (Accolate) and zileuton (Zyflo, Zyflo CR). Potential side effects of leukotriene modifiers include behavior and mood changes and suicidal thoughts. Talk to your doctor if you experience these signs or symptoms.
Don't rely only on quick-relief medications
You can also use pre-exercise drugs as a quick-relief treatment for symptoms. However, you shouldn't need to use your pre-exercise inhaler more often than your doctor recommends.
Keep a record of how many puffs you use each week, how often you use your pre-exercise inhaler for prevention and how often you use it to treat symptoms. If you use it daily or you frequently use it for symptom relief, your doctor may adjust your long-term control medication.
Steps you can take to prevent or minimize symptoms of exercise-induced bronchoconstriction include the following:
Do a 10-minute warm-up that varies in intensity before you begin regular exercise.
Breathe through your nose to warm and humidify the air before it enters your lungs.
Wear a face mask or scarf when exercising, especially in cold, dry weather.
If you have allergies, avoid triggers. For example, don't exercise outside when pollen counts are high.
Avoid strenuous exercise if you have a cold or other respiratory infection.
Exercise regularly to stay in shape and promote good respiratory health.
Talk to your doctor about writing an action plan if your child experiences exercise-induced bronchoconstriction. This document provides step-by-step instructions for teachers, nurses and coaches that explain what treatments your child needs, when treatments should be administered and what to do if your child experiences symptoms.
There is limited clinical evidence of alternative therapies that may modify the severity of exercise-induced bronchoconstriction or provide additional benefit to standard treatments. Possible beneficial interventions include:
A low-salt diet
Fatty fish, such as salmon and tuna, or fish oil supplements
Fruits and vegetables rich in vitamin C (strawberries, oranges, broccoli, leafy vegetables and others) or vitamin C supplements