Exercise-induced asthma is a common term used to describe respiratory symptoms like coughing, wheezing, or shortness of breath triggered by physical activity. The medically preferred and more accurate term for this condition is Exercise-Induced Bronchoconstriction, or EIB. EIB describes a temporary narrowing of the airways that occurs during or immediately following intense exercise. While EIB is a frequent occurrence in people who also have chronic asthma, it is important to understand that EIB can also affect individuals who do not have a formal asthma diagnosis. This distinction is significant because EIB is a response to a specific physical trigger, whereas chronic asthma involves persistent, underlying airway inflammation.
Understanding Exercise-Induced Bronchoconstriction
The physiological mechanism behind EIB is centered on the rapid movement of air, known as hyperventilation, required during vigorous activity. When the body works hard, people switch to mouth breathing, bypassing the nose’s natural function of warming and humidifying inhaled air before it reaches the lungs.
The influx of cooler, drier air causes the airway lining to lose heat and water through evaporation. This evaporative water loss creates a hyperosmolar environment, meaning the fluid lining the airways becomes highly concentrated. This change triggers mast cells to release inflammatory mediators like leukotrienes and histamine. The release of these mediators causes the smooth muscle surrounding the bronchial tubes to contract, leading to the transient airway narrowing. Common environmental triggers that exacerbate this process include exercising in cold, dry air or high-allergen environments.
Factors Influencing EIB Resolution
The question of whether EIB can completely resolve is complex, but the condition is generally considered transient and manageable rather than a permanent state. The prognosis for improvement often depends on whether the individual has isolated EIB or EIB coupled with underlying chronic asthma. For individuals with underlying asthma, EIB is frequently a sign that their chronic condition is not well-controlled, and improving the management of the asthma itself is the primary pathway to reducing EIB severity.
For those with isolated EIB, where no chronic inflammation is present, the long-term outlook for significant improvement or near-resolution is generally better. In the pediatric population, EIB severity may show a moderate negative correlation with age, suggesting that the condition can lessen as a child grows older. However, some research indicates that while the severity may decrease, the recovery rate from an episode of EIB may actually slow down with increasing age in childhood. Consistent management and control of symptoms allow many individuals with isolated EIB to lead fully active lives, often to the point where symptoms are negligible.
Confirming the Diagnosis
Respiratory symptoms alone, such as coughing or shortness of breath during exercise, are not sufficient to accurately diagnose EIB, as they can be associated with other conditions. Objective testing is therefore necessary to definitively confirm the presence of EIB. The standard diagnostic procedure involves a lung function test called spirometry, which measures the volume and flow of air that can be inhaled and exhaled.
Spirometry is performed before and after a standardized exercise challenge test. The challenge typically requires the person to exercise vigorously on a treadmill or cycle ergometer for a set period, often six to eight minutes, to achieve a near-maximal heart rate. After the exercise, spirometry measurements are repeated at specific intervals over the next 15 to 30 minutes. A diagnosis of EIB is confirmed if the forced expiratory volume in one second (FEV1) drops by 10% or more from the pre-exercise baseline measurement. Alternative laboratory challenges, such as the eucapnic voluntary hyperventilation (EVH) test, can also be used to mimic the hyperventilation of exercise in a controlled setting.
Long-Term Management and Safe Exercise Strategies
Managing EIB involves a dual strategy of both pharmacological intervention and careful non-pharmacological planning to ensure safe and symptom-free activity. The most common pharmacological approach is the prophylactic use of a short-acting beta-agonist (SABA) inhaler, such as albuterol. This quick-relief medication is typically taken 15 to 30 minutes before exercise to relax the airway muscles and prevent bronchoconstriction before it starts.
If symptoms are frequent, or if EIB occurs alongside chronic asthma, a healthcare provider may recommend long-term control medications. These may include daily inhaled corticosteroids (ICS) to reduce underlying airway inflammation or leukotriene receptor antagonists (LTRAs) taken orally to block the release of inflammatory mediators. The goal of a daily controller medication is to maintain overall airway health, making the airways less reactive to exercise triggers.
Non-pharmacological strategies are equally important for safe exercise:
- A proper warm-up routine of 10 to 15 minutes of light-to-moderate activity can induce a refractory period, helping the lungs become less reactive to subsequent strenuous exercise.
- A gradual cool-down is recommended at the end of the activity.
- Avoid exercising outdoors on days with high pollen or air pollution counts.
- When exercising in cold, dry conditions, covering the mouth and nose with a scarf or mask can help warm and humidify the air before it enters the airways.
- Practicing nasal breathing during less intense parts of the workout helps preserve the warmth and moisture in the air reaching the lungs.