By Victor Lun, MD
The underlying cause of EIB is the change in airway temperature and humidity levels during high rates of breathing during exercise. These changes lead to airway muscle constriction and airway inflammation, which then cause airway narrowing.
Those with EIB will experience chest tightness, breathlessness, coughing, and wheezing occurring after several minutes of stopping exercise. The airway narrowing usually reaches a peak at 5 to 10 minutes and then gradually resolves after 30 to 60 minutes. Symptoms less commonly occur during exercise, unless one is asthmatic. EIB can be worse if exercising in cold, dry and/ or polluted air and if one’s asthma is not well controlled.
If one suspects EIB, they should see a physician to undergo a thorough medical assessment as other conditions can also the cause the symptoms of EIB.
Several breathing tests can be used to help diagnose asthma and EIB, including: pulmonary function testing, B2-agonist challenge test, eucapnic voluntary hyperpnea test (EVH test), methacholine challenge test, and exercise challenge test (lab and field test).
Strategies that have been found to lessen the severity of EIB including exercising in a warm and humid environments or using a face-mask to create a warm air re-breathing environment and an aerobic warm-up at a sub-threshold intensity for 15-30 minutes at least 30 minutes before competition or more vigorous activity is performed to engage a refractory period.
Medications that can be used to prevent EIB include inhaled short and long acting B agonists (eg. salbutamol, salmeterol), cromolyn sodium, and nedocromil sodium. To be effective, these medications should be taken at 30 minutes prior to starting any exercise and can last for 4-6 hours. If symptoms do not change with the use of these medications, then inhaled corticosteroids, inhaled combined long-acting B agonist-corticosteroid and oral anti-allergy (eg. montelukast) medications could be tried.
Dr. Victor Lun, MSc., MD, CCFP, Dip. Sport Med (CASEM is a Sport Medicine doctor who practices at the University of Calgary Sport Medicine Centre. He is the team physician for several the winter and summer sport Canadian national sport teams and a medical director at the Canadian Sport Centre Calgary.
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