Asthma or exercise induced bronchoconstriction – is there a difference?

Reference: May-June 2025 | Issue 3 | Vol 18 | Page 52

Exercise can frequently trigger asthma symptoms and up to 90 per cent of people with asthma experience EIB

Exercise-induced bronchoconstriction (EIB) describes a transient and reversible contraction of bronchial smooth muscle after physical exertion that may or may not produce symptoms of dyspnoea, chest tightness, wheezing, and cough.¹ Although anyone can have EIB, it is more common in high-level athletes. An estimated 5-20 per cent of the general population and up to 90 per cent of people with asthma experience EIB. 

The term EIA (exercise-induced asthma) has given way to the distinction between EIB with asthma (EIBA) and EIB without asthma (EIBwA). EIBA refers to bronchial obstruction occurring after exercise in individuals with clinical asthma symptoms, while EIBwA relates to bronchial obstruction in those without other signs of asthma.

The prevalence of asthma, EIB, allergic, and non-allergic bronchitis is notably higher in athletes, and it can be influenced by factors such as the type of sport, training environment, and genetics. Asthma is estimated to affect 15-30 per cent of Olympic athletes, with most engaged in endurance events, such as swimming, long-distance running, and cycling.²

Exercise can frequently trigger asthma symptoms and some individuals with asthma avoid physical activity because of this. In the EIB Landmark Survey,³ EIB resulted in 22.2 per cent of children aged between four and 12 years with asthma, and 31.8 per cent of those aged between 13 and 17 with asthma, avoiding sports activities. This avoidance can exacerbate health issues, leading to a cycle of declining fitness and skeletal muscle deconditioning.

Exercise is an important part of a healthy lifestyle and has been shown to:

• Increase endurance capacity;
• Improve lung function;
• Reduce airway inflammation;
• Increase the overall quality of life.⁴

In physically active people with moderate/severe asthma, physical activity interventions are associated with reduced symptoms and improved quality of life.⁵

Causes

It is not exactly clear what causes EIB. For a long time, the cause was thought to be cold air, however, recent studies found dry air to be a more likely culprit. Cold air contains less moisture than warm air. Breathing in cold, dry air results in dehydration of the air passages causing them to constrict and reducing the air flow. Other factors, such as chlorine or other fumes, can cause irritation of the lining of the airways and contribute to breathing difficulties as well.

Common triggers

• Dry air;
• Cold air;
• Air pollution;
• Pollen;
• Chlorine in swimming pools;
• In a gym setting, fumes from perfume, paint, new equipment or carpet;
• Activities with long periods of deep breathing, such as long-distance running, swimming or football.

Diagnosis

EIB is primarily diagnosed through exercise challenge tests (ECT), with an emphasis on airway responsiveness during the bronchoprovocation challenge. History and symptom patterns help confirm the diagnosis. The exercise test undoubtedly stands out as one of the most effective methods for inducing EIB, with a decline in FEV1 (forced expiratory volume in one second) of 10 per cent or more from the baseline being diagnostic of EIB.

During an ECT, the aim is to run on a treadmill or use other stationary exercise equipment to increase breathing rate. The exercise needs to be intense enough to trigger symptoms. If needed performing a real-life exercise challenge, such as climbing stairs can be useful in the absence of gym equipment. Spirometry tests before and after the challenge can provide evidence of EIB. This is then followed with a bronchodilator reversibility test.

Several adjustments should be considered when conducting the ECT:

• Intensity and duration are pivotal factors in provoking bronchoconstriction, the ideal ECT protocol should involve high ventilation and maintain temperature (20-25 degrees Celsius) and humidity at controlled levels (<50%). If the air is too cold or dry, this in itself can result in bronchospasm.
• Sport-specific ECTs are preferable in elite athletes over laboratory-based ECT.

Direct challenge tests such as methacholine and inhaled histamine testing are considered more accurate in assessing EIBA. Indirect challenge tests encompass exercise, hypertonic saline, and inhaled mannitol powder tests. These are more precise in diagnosing EIBwA.

FeNO (fractional exhaled nitric oxide) testing has a limited role in diagnosing EIB. A recent multi-centre retrospective analysis involving 488 athletes demonstrated that FeNO levels of ≥40 parts per billion offers good specificity, allowing it to be useful in confirming a diagnosis of EIB. However, given its limitations in sensitivity and predictive values, FeNO should not be used as a substitute for indirect bronchial provocation testing in athletes.⁶

Management

The overall management of EIB, whether with or without underlying asthma, should align with similar principles for both athletes and non-athletes. The general guidelines for symptom control, prevention of exacerbations, avoidance of airflow limitation, trigger factor management, and reducing the risk of asthma-related complications should be followed. Any comorbidities such as gastroesophageal reflux disease, allergic rhinitis, and sinusitis should be addressed and managed. Minimising exposure to allergens is of paramount importance in managing EIB effectively.

Warm-ups: While there is no consensus on the ideal warm-up time, common recommendations advocate for 10-15 minutes. This warm-up typically involves resistance and stretching exercises, with the goal of achieving a heart rate around 50-60 per cent of the maximum heart rate.

Pharmacological management

The pharmacological therapy for EIB in individuals with asthma follows the same principles as the general treatment for asthma. The primary long-term goal is to reduce airway inflammation and prevent bronchoconstriction. This is typically achieved using inhaled corticosteroids (ICS) in individuals with persistent or frequent EIB symptoms. ICS can be used either as monotherapy or as combination therapy.

Short-acting beta agonists (SABA) provide quick relief from EIB symptoms by relaxing the smooth muscles in the airways. While athletes may use SABAs as a quick-relief inhaler before exercise to prevent bronchoconstriction, recent studies and recommendations discourage the use of SABA as a sole treatment.

Adults with mild asthma are advised to use as-needed ICS/formoterol rather than regular ICS maintenance treatment along with as-needed SABA. Similarly, adolescents with mild asthma are recommended to use as needed ICS/formoterol instead of as needed SABA.⁷

Leukotriene receptor antagonists block the action of leukotrienes, reduce EIB and have protective effects against bronchoconstriction caused by exposure to pollutants and cold air.

Advice for patient with asthma who wish to exercise:

• Take asthma medication as prescribed.
• Manage asthma triggers.
• Have an Asthma Action Plan in place.
• Always warm up gently for approximately 15 minutes before more vigorous exercising and cool down afterwards.
• Always carry a reliever inhaler.
• If asthma is triggered during exercise, take reliever inhaler (low dose formoterol/budesonide or salbutamol) approximately 15 minutes before warming up.⁸
• If exercising alone, make sure someone knows where the athlete is and what time they are due to return.

If asthma is triggered by pollen:

• Check the pollen forecast at www.pollen.ie
• Avoid exercising outside when the pollen count is high.
• Have an allergic rhinitis medication plan in place.
• Pollen avoidance strategies.