Asthma is a condition that makes the airway inflamed and narrow and thus leads to difficulty in breathing. Exercise-induced asthma or Exercise-induced bronchoconstriction (EIB) is described as a transient and reversible constriction of bronchial smooth muscles after physical exertion that may or may not be accompanied by symptoms like difficulty in breathing, tightness in the chest, whistling sound while breathing (wheezing) and cough. It can occur in 40 to 90% of people having asthma or 20% of the people without asthma as well.
- Exercise-Induced Bronchoconstriction (EIB)
- EIBa – EIB with asthma
- EIBwa – EIB without asthma
Generally, people tend to avoid exercises to avoid EIB but ironically, regular engagement in physical activities tends to improve EIB severity, and lung function and reduce airway inflammation.
The occurrence of EIB episodes depends upon the sport being played,
- High-risk sports ****
Include long episodes of exercise greater than 5 to 8 minutes in an environment such as cold, dry air, or chlorinated pools.
Eg – Long-distance running, swimming, triathlons
- Medium-risk sports ****
Includes continuous activity for not more than 5 to 8 minutes
Eg – soccer, rugby, football, baseball, cricket
- Low-risk sports ****
Includes non-long distance track events
Eg – Sprints, tennis, gymnastics, boxing, golf, weightlifting
Causes
EIB results in an alteration of normal lung functioning because of water loss in the airways (osmotic theory), temperature changes in the body, and irritant exposure because of increased mouth breathing (as nasal breathing becomes insufficient).
In a normal scenario, the air you breathe needs to be heated and moisturized because warm, humid air is easier to breathe in and this function is taken care of by the nostrils. But as an individual puts more physical exertion on the body, nasal breathing switches to mouth breathing to cater to the increased demand and as the mouth doesn’t have the functionality to warm and moisten the air or to filter out the dust particles or allergens, the air one breathes is drier, cooler and contains more irritants. This all can irritate the airways and thus lead to bronchoconstriction and inflammation and finally difficulty in breathing.
Another widely accepted explanation behind the EIB mechanism is Osmotic Theory or Water-loss Hypothesis. It suggests that increased ventilation in the airways during the period of physical activity leads to water loss from the airway surfaces due to evaporation, thus leading to dehydration of the airways and as a result, osmoreceptors trigger increased blood flow in the bronchioles causing edema. Also, this increased osmolarity leads to the release of mediators that results in the contraction of smooth muscles and thus further obstructs the airway.
Symptoms and Risk Factors
Symptoms of EIB may vary from person to person but they can include
- Mild to moderate symptoms of chest tightness
- Wheezing (whistle or coarse sound while breathing when the airway is blocked)
- Coughing
- Dyspnoea (shortness of breath)
- Mucus
The severity of symptoms depends upon the outside environment such as cold, dry, or humid conditions along with the concentration of respiratory irritants in the air. Symptoms may occur 15 minutes after 5 to 8 minutes of intense workout and may resolve within 30 to 90 minutes.
Risk factors include
- Personal or family history of asthma
- History of allergic rhinitis
- Smoking or exposure to cigarette smoke
- Involvement in high-risk sports
- Female gender
- Play sports in cold, dry air
- Viral respiratory infection
Diagnosing EIB just with symptoms has a low success rate and some specific tests need to be done to understand the root cause in detail because treatment needs to be planned accordingly. EIB is not a life-threatening condition if managed well with pharmacotherapy, some breathing exercises, and taking necessary precautions in the sports involving major risk factors.
Reference list
- Aggarwal, B., Mulgirigama, A. and Berend, N. (2018). Exercise-induced bronchoconstriction: prevalence, pathophysiology, patient impact, diagnosis and management. npj Primary Care Respiratory Medicine, [online] 28(1).
- Gerow, M. and Bruner, P.J. (2020). Exercise Induced Asthma. [online] PubMed.
- Khajotia, R. (2008). Exercise-induced asthma: fresh insights and an overview. Malaysian family physician : the official journal of the Academy of Family Physicians of Malaysia, [online] 3(1), pp.21–4.
- Nunez, K. (2021). Exercise-Induced Asthma: Symptoms, Causes, Treatment, Prevention. [online] Healthline.
