Exercise-Induced Bronchoconstriction

Etiology

EIB refers to a temporary narrowing of the airways during physical activity. A rapid increase in airflow during exercise requires the airways to warm and humidify large volumes of incoming air, triggering the condition. In susceptible individuals, this process leads to inflammatory, neuronal, and vascular responses, resulting in bronchial smooth muscle contraction. 

Epidemiology

EIB occurs in 40% to 90% of individuals with asthma and up to 20% of the general population without asthma.[1][2][3] Elite athletes have an increased prevalence, ranging from 30% to 70%, with higher rates observed in women and those participating in winter sports.[1][3][8] Asthma is a global health concern, affecting approximately 260 million people worldwide. EIB may serve as an indicator of poor asthma control.[3] Each year, asthma is responsible for nearly 420,000 deaths globally.[3][9][10][11]  

Risk factors for EIB include a personal or family history of asthma, a personal history of atopy or allergic rhinitis, exposure to cigarette smoke, participating in high-risk sports, and living and practicing in areas with high levels of pollution.[12][13] Results from several small studies suggest sugar-sweetened beverages may increase risk by increasing inflammation and adiposity.[14][15] The likelihood of experiencing EIB varies depending on the type of sport. High-risk sports typically involve prolonged periods of continuous exercise lasting more than 5 to 8 minutes, often in environments with cold, dry air or exposure to irritants like chlorine. These sports include long-distance running, cycling, cross-country or downhill skiing, ice hockey, ice skating, high-altitude sports, swimming, water polo, and triathlons. Medium-risk sports, such as soccer, rugby, football, basketball, volleyball, baseball, cricket, and field hockey, generally involve shorter bursts of activity, with athletes rarely exercising continuously for more than 5 to 8 minutes. Low-risk sports, such as sprinting, tennis, fencing, gymnastics, boxing, golf, weightlifting, bodybuilding, and martial arts, are less likely to trigger EIB due to the intermittent or short duration of exertion.[2]

Pathophysiology

EIB arises from disruptions in normal lung physiology caused by evaporative water loss, temperature changes, and exposure to irritants during exercise-induced hyperpnea. During intense physical activity, minute ventilation can increase to 200 L/min, leading to airway cooling and mucosal dehydration.[1][16][17] As airway cells lose water, their osmolality increases, causing cell shrinkage, which triggers coughing, increased mucus production, and an epithelial barrier breakdown. In response, cells attempt to restore volume by drawing fluid from the submucosa, resulting in airway edema and releasing inflammatory mediators, such as histamine, leukotrienes, prostaglandins, and mast cell products.[16]

Bronchial blood flow also increases, generating reactive oxygen species, contributing to oxidative stress and lipid peroxidation.[1][6][9][16][17] Additionally, activation of sensory and autonomic nerves leads to both direct and neuronal pathways of bronchoconstriction.[1][17] As nasal breathing becomes insufficient during vigorous exercise, individuals switch to mouth breathing. This increases exposure of lung surfaces to pollutants, irritants, and allergens, further promoting reactive oxygen species and triggering a neutrophilic inflammatory response (see Image. Pathophysiology of Asthma).[2][3][14] 

Some research suggests that individuals genetically unable to counteract oxidative stress with antioxidants such as glutathione may have an increased risk of developing EIB.[14] This impaired antioxidant defense may enhance susceptibility to airway inflammation and damage during high levels of respiratory stress. Alterations in mucus composition and impaired mucociliary clearance during exercise can contribute to mucus plugging and the growth of bacteria.[16] This environment creates favorable conditions for respiratory infections and may exacerbate airway inflammation in susceptible individuals.

Intense physical training can cause transient immune suppression, shifting the immune response toward a type 2 lymphocyte pattern. This shift is associated with increased rates of atopy and viral upper respiratory infections.[2] Prolonged exposure to airway stress can lead to epithelial damage, cell shedding, and airway remodeling that resembles asthma. However, this process is partially reversible, as study results show that lung damage and airway hyperresponsiveness can improve over weeks to years once exposure and intense exercise are reduced or discontinued.[2][3]

Evidence linking the severity of symptoms to the rate of airway water loss supports the osmotic theory of EIB. Inhaling fully humidified air at body temperature can help prevent EIB, whereas inhaling hyperosmolar saline can provoke bronchoconstriction.[16] Research also demonstrates elevated numbers of epithelial cells in sputum samples and increased exhaled nitric oxide levels in individuals with EIB, indicating heightened airway inflammation and epithelial injury.[1] Environmental exposure to pollutants, such as fossil fuels, ozone, and trichloramine, especially in ice rinks, practice fields near major roadways, and swimming pools, has been shown to exacerbate EIB.[1][2] High-pollen environments can also worsen symptoms. 

History and Physical

Symptoms of EIB can range from mild to moderate symptoms of chest tightness, wheezing, coughing, and dyspnea. At the onset of exercise, patients with EIB have a period of bronchodilation that lasts approximately 5 to 8 minutes, followed by bronchoconstriction. Bronchoconstriction peaks within 10 to 15 minutes and typically resolves within 30 to 90 minutes, followed by a refractory period of 1 to 3 hours, during which continued exercise does not cause bronchoconstriction.[1][2][3] The refractory period is most likely due to inhibitory prostaglandins, like prostaglandin E2.[18]

Although rare, there have been reports of severe EIB symptoms leading to respiratory failure and death. Some individuals may remain asymptomatic, contributing to underdiagnosis. The physical examination is often unremarkable in clinical settings. Clinicians should look for signs of atopy, acute or chronic sinus or pulmonary infection, allergic disease, heart murmurs, edema, or abnormal lung sounds.

Evaluation

Except for patients with an established asthma diagnosis and typical asthma symptoms associated with exercise, establishing a clinical diagnosis based on symptoms alone has low sensitivity and specificity. Clinicians establish the diagnosis based on a combination of clinical symptoms and objective exercise or alternative challenge testing. Standardized testing for diagnosis includes both direct and indirect methods.[19] Usually, testing involves measuring changes in spirometry measurements of the forced expiratory volume in 1 second (FEV1), expressed as a percentage of the decrease from baseline following the challenge.[1][3][7]

Pulmonary Function Testing

The first step in evaluating suspected EIB is pulmonary function testing with spirometry. This test helps establish baseline pulmonary function, assess for other conditions that may mimic asthma, and identify evidence of obstructive or restrictive lung disease.[4] If baseline spirometry is normal, further challenge testing may be necessary to confirm the diagnosis of EIB.

Exercise Challenge Testing

An exercise challenge test is the preferred method for diagnosing EIB.[1] Testing should follow specific parameters, including achieving target ventilation and elevating heart rate to 80% to 90% of the predicted maximum. This exercise should be conducted in a controlled, dry environment, and last 6 to 10 minutes, typically using a treadmill or ergometer. To ensure test accuracy, patients must avoid entering the postexercise refractory period, withhold certain medications, such as bronchodilators, and refrain from consuming caffeine or engaging in vigorous exercise on the test day. These precautions help prevent false-negative results and ensure that, if present, bronchoconstriction is accurately detected during testing. 

Spirometry, particularly FEV₁, is measured at multiple intervals following exercise, typically at 5, 10, 15, and 30 minutes. A decrease in FEV₁ of 10% or more confirms the diagnosis of EIB, with severity classified as mild (10% to <25%), moderate (25%- 50%), or severe (>50%). Some centers use a 15% decrease in FEV₁ as a more specific diagnostic threshold. Because test reproducibility is approximately 76%, repeat testing may sometimes be necessary to confirm the diagnosis. Despite these limitations, the exercise challenge test remains the most direct and preferred method for diagnosing EIB.[1] 

Alternative Provocation Tests

Clinicians can use alternative provocation tests, such as eucapnic voluntary hyperventilation, methacholine, histamine, or mannitol inhalation, when an exercise challenge is not feasible or when the test results are negative in a patient with a high clinical suspicion for EIB.[20] These tests are useful for confirming the diagnosis when the exercise challenge test is inconclusive. Eucapnic voluntary hyperventilation is the most sensitive alternative test for EIB. Additionally, methacholine's direct stimulation of smooth muscle receptors to induce bronchoconstriction is well established, with a sensitivity of 58.6% to 91.1%.[7] 

The International Olympic Committee and the World Anti-Doping Agency require athletes to undergo a challenge test to document asthma before allowing the use of medications like bronchodilators during international competitions.[20] This policy is based on the need for objective evidence to confirm the diagnosis of asthma or EIB due to the poor predictive value of respiratory symptoms alone in athletes.[20][21]

Allergy Testing

Clinicians should consider skin allergen testing or a radioallergosorbent test to identify specific allergens contributing to symptoms. Identifying these triggers can guide patients in avoiding causative antigens and inform decisions about initiating allergen-specific immunotherapy if indicated.  

Fractional Excretion of Nitric Oxide Testing

Results from several smaller studies suggest that fractional excretion of nitric oxide (FENO) may replace FEV₁ in diagnosing and measuring the severity of EIB. FENO testing can be used alongside direct or indirect challenge tests and is particularly helpful for younger children due to its ease of administration. FENO measures the T helper cell type 2 (Th2)-mediated airway inflammation, offering a different diagnostic perspective than airway responsiveness; this may make it more effective in distinguishing EIB from other causes of respiratory symptoms. Experts propose cut-off values of 27 to 46 parts per billion (ppb) FENO as diagnostic, with greater than 46 ppb being 100% specific.[22][23][24]

Additional Testing

The patient's history and physical examination should guide the selection of additional testing. Additional considerations are based on clinical context:

• Serum thyroid-stimulating hormone: Useful if anxiety is suspected to be mimicking asthma symptoms
• Chest and lateral neck radiographs: Recommended for patients older than 40 with new-onset asthma, or those presenting with atypical symptoms such as hemoptysis, persistent, localized wheezing, fever, weight loss, dysphonia, concern for foreign body, or significant hypoxemia
• Echocardiography: Indicated in patients with chest pain, cyanosis, a heart murmur, or syncope to assess cardiac valvular function and overall cardiac contractility
• Continuous laryngoscopy during exercise: Useful for evaluating exercise-induced laryngeal obstruction (EILO), which is typically characterized by inspiratory stridor, dyspnea that occurs only at the peak of vigorous exercise, and rapid symptom resolution upon cessation of activity
  • EILO is identified by moderate to severe adduction of laryngeal structures during exertion.
• Laryngoscopy: Appropriate for assessing potential causes such as gastroesophageal reflux, foreign body, or inducible laryngeal obstruction
• Upper endoscopy: Recommended for patients with suspected reflux and alarm symptoms like new onset reflux in a patient 60 or older, dysphagia, unexplained weight loss, iron deficiency anemia, gastrointestinal cancer in a first-degree relative, and gastrointestinal bleeding

Treatment / Management

Clinicians monitor the response to therapy based on clinical symptoms and the patient's ability to tolerate exercise. Objective measures, such as pre- and postexercise FEV1, can provide valuable information. However, this is often substituted with peak expiratory flow measurement in clinical practice. See StatPearls' companion topic, "Peak Flow Rate Measurement," for an in-depth discussion on the proper technique and clinical uses of peak flow measurement. A repeat exercise challenge test may be used to evaluate the effectiveness of therapy and guide ongoing management.

Nonpharmacologic Interventions

Management of EIB begins with nonpharmacological strategies.[1] Improving cardiovascular fitness, building endurance, and promoting weight loss in patients with obesity can help mitigate symptoms. A Cochrane review and results from other studies show that regular exercise improves pulmonary function, decreases airway inflammation, and reduces the severity of EIB, particularly in patients with asthma.[1][2][3][25][26] (A1)

Study results are conflicting regarding the effectiveness of preexercise warm-ups; some evidence suggests that variable and high-intensity warm-ups reduce the fall in FEV1.[16][27] Breathing warm, humid air lessens the degree of bronchoconstriction. Athletes should consider wearing a thin scarf or a mask in cold or dry climates. Heat and moisture exchanger masks, which warm and humidify inspired air, may reduce symptom severity and reduce medication need.[27][28]

Patients should also avoid exercising in environments with high pollen, chlorine, ozone, or other pollutants. Wearing a mechanical barrier mask or selecting lower-risk sports can minimize exposure. In aquatic sports, alternative pool disinfection methods may help reduce symptom exacerbation.[3][27] Additional supportive measures include preexercise caffeine intake, which may reduce bronchoconstriction, lower ventilatory dead space, and lessen exercise-induced hypoxemia and respiratory muscle fatigue. Results from studies investigating several dietary modifications for treating EIB reveal a potential benefit of a low-sodium diet. However, fish oil, lycopene, vitamin C, and vitamin E have not demonstrated consistent benefits.[1][27][29](A1)

Another treatment approach focuses on reducing the perception of symptoms. Breathing control techniques, including yoga or supervised breathing training, have been shown in some small studies to decrease symptoms, reduce medication use, decrease anxiety and depression associated with EIB, and increase quality of life. However, further research and adaptation are needed before these methods can be widely recommended for patients with EIB.[27] 

Respiratory muscle training involves using proper breathing techniques and devices to strengthen both inspiratory and expiratory muscles. A Cochrane review found no evidence for or against respiratory muscle training in patients with EIB. Nevertheless, respiratory muscle training is promising for patients with chronic obstructive pulmonary disease, EILO, and stridor, making it a promising, low-cost adjunctive therapy for individuals with EIB.[25][27]

Pharmacologic Interventions

Before initiating pharmacologic therapy, clinicians must ensure patients can use inhalers correctly. Improper technique can significantly reduce medication delivery to the lungs and diminish therapeutic effectiveness. 

Short-acting ß-agonists 

All patients with EIB should have access to a SABA, such as albuterol. SABAs work by relaxing airway smooth muscles and inhibiting mast cell degranulation.[30] The usual dose is 2 to 4 puffs; patients with frequent symptoms of EIB should use 2 puffs of albuterol as a preventative measure, 5 to 20 minutes before exercise.[1] Alternatively, 1 puff of budesonide-formoterol 160 µg/4.5 µg is an appropriate option. (A1)

With frequent SABA use, tolerance can develop, likely due to the downregulation of the ß2 receptors. Ipratropium is not recommended for rapid symptom relief due to its delayed onset of action.[1][31] However, it can be a viable option for pretreatment for patients unable to tolerate SABAs. Ultimately, the goal is adequate control of underlying asthma so that routine SABA use before exercise becomes unnecessary.(A1)

Inhaled corticosteroids 

Study results estimate that 15% to 20% of the patients will not respond to SABA treatment alone. If symptoms remain uncontrolled or if the patient is using a SABA daily, this often indicates poorly controlled asthma. Before escalating therapy, clinicians should confirm the patient's adherence and correct use of current medications. Step-up therapy should be implemented according to the severity of asthma in patients with underlying asthma. See StatPearls' companion topics, "Pediatric Asthma" and "Asthma," for an in-depth discussion on diagnosing and treating asthma in adults and children.

Daily leukotriene receptor antagonists (LTRAs) or inhaled corticosteroids (ICSs) are first-line choices for patients with EIB without underlying asthma who require additional therapy. Additionally, patients who engage in prolonged exercise, exercise multiple times a day, or children with irregular schedules who play at various times risk developing tachyphylaxis from repeated dosing of ß2-agonists. These patients should receive daily LTRAs or ICSs in addition to SABAs. 

Leukotriene receptor antagonists 

Daily LTRAs address the release of inflammatory mediators involved in EIB.[1][31] Agents such as montelukast, zafirlukast, and zileuton provide longer-lasting bronchodilation and are not associated with tolerance. A single dose of LTRAs can provide protection within 2 hours. The choice between ICS and LTRA is patient-specific.[1] (A1)

Mast cell stabilizing agents 

Mast cell degranulation plays a key role in EIB pathology. The American Thoracic Society (ATS) recommends adding an inhaled mast cell stabilizing agent, such as sodium cromoglycate or nedocromil sodium, before exercise in patients who continue to experience frequent symptoms despite using an inhaled SABA.[1] These medications are unavailable in the United States, but are readily accessible in many other countries.[1](A1)

Antihistamine

The ATS recommends adding a daily antihistamine in patients with allergies who continue to experience frequent symptoms despite using an inhaled SABA before exercise.[1] Antihistamines provide no additional benefit in nonatopic individuals. (A1)

Noninvasive Positive Pressure Ventilation  

Results from a recent study exploring noninvasive positive pressure ventilation (NIPPV) as a nonpharmacologic treatment for EIB revealed that airway stretching activates inhibitory pathways that reduce inflammation and promote bronchodilation. Participants underwent ten 1-hour sessions over 5 weeks, beginning with 20 minutes of respiratory exercises in seated and supine positions. They then received continuous positive airway pressure (CPAP) at 8 cm H2O, inspiratory muscle training, or bilevel positive airway pressure (BiPAP) at 8 to 12 cm H2O. Outcome measures include exercise-induced changes in FEV1 according to ATS criteria, fractional exhaled nitric oxide to assess airway inflammation, and symptom scoring via questionnaire. CPAP and BiPAP significantly reduce EIB, while respiratory muscle training decreases medication use and improves respiratory muscle strength. These findings suggest that noninvasive positive pressure ventilation and respiratory training may offer effective nonpharmacologic options for managing EIB.[17](B3)

Differential Diagnosis

Although chest tightness, wheezing, coughing, and shortness of breath during exercise may suggest EIB, these symptoms can also result from other conditions involving the upper or lower airways, cardiovascular and gastrointestinal systems, or dysfunctional breathing patterns.[32] Healthcare professionals must consider a broad list of diagnoses when evaluating patients with exertional dyspnea. Diagnosing EIB can be particularly challenging due to the possible absence of other asthma signs, normal baseline spirometry, and lack of response to bronchodilator pretreatment.

Nasal Airway

• Exercise-induced rhinosinusitis
• Allergic rhinitis
• Upper airway cough syndrome
• Upper respiratory infection 
• Anatomic abnormalities 

The nasal airway helps filter, humidify, and regulate airway resistance. Conditions affecting the nasal airway are often comorbid with EIB.[8][33] Management of upper airway diseases includes avoiding triggers and irritants, as well as MCSAs and LTRAs, using intranasal corticosteroids, taking decongestants, and undergoing immunotherapy.[1][2][4][8][33]

Pharynx and Larynx

• EILO
• Exercise-induced laryngomalacia
• Exercise-induced laryngopharyngeal reflux [1][2][4][8]

Lower Airways

• Airway obstruction due to malignancy
• Interstitial lung disease
• Chronic obstructive pulmonary disease
• Infection [1][2][4][8]

Cardiac

• Coronary artery disease
• Poor cardiovascular conditioning
• Exercise-induced dysrhythmias [6]

Others

• Exercise-induced anaphylaxis
• Anxiety disorder
• Exercise-induced pulmonary edema
• Pulmonary embolism
• Saltwater aspiration syndrome [4] 

Prognosis

The prognosis of EIB is generally favorable, especially when the condition is accurately diagnosed and effectively managed. Most individuals experience mild to moderate symptoms such as chest tightness, coughing, wheezing, and shortness of breath, which may impair athletic performance but rarely lead to severe respiratory distress. With appropriate pharmacologic and nonpharmacologic interventions, including preexercise bronchodilator use and environmental modifications, patients can often fully participate in physical activity and excel in competitive sports at an elite level.

However, clinicians must recognize that severe episodes of EIB, though rare, can lead to significant respiratory compromise, including isolated cases of respiratory failure and death. Early identification, patient education, and individualized management strategies are, therefore, critical to optimizing outcomes and preventing complications. Ongoing monitoring and reassessment are also important to ensure sustained control of symptoms and to support long-term health and physical performance.

Complications

EIB can lead to significant complications if not properly managed. Commonly, individuals may experience limitations in physical activity, which can reduce overall fitness and contribute to a sedentary lifestyle. While most cases are mild to moderate, rare severe episodes can result in significant respiratory distress or, in extreme cases, respiratory failure.

The United States Food and Drug Administration has issued a boxed warning for montelukast, an LTRA, regarding the risk of behavior and mood-related changes. Reported symptoms are agitation, depression, insomnia, suicidal thoughts, and actions. However, research findings are mixed, and some experts believe that worsening asthma control in those who require LTRA initiation may play a role in behavior and mood changes. Results from a recent nationwide register-based cohort study from Sweden found no association between the use of montelukast and the risk of neuropsychiatric adverse events.[34] Results from other observational studies, however, reported a small increased risk of neuropsychiatric changes.[35][36]