Exercise-Induced Asthma

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Are athletes at greater risk of developing asthma than their non-athletic counterparts?

 

Asthma is the most common respiratory disease in the UK, with a prevalence of approximately 10-15%. The development of asthma can be impacted by immunological, genetic, hygiene and environmental factors. The exact reasons for the high number of asthma sufferers are unclear, although many speculate in the western world that it is due to aero-allergens (such as pollen and dust) and the ever increasing amount of pollutants being pumped into our atmosphere.

Asthma can be defined as both a chronic and acute inflammatory disorder of the airways, associated with airway hyperresponsiveness to changes in atmospheric air. Our genes and exposure to allergens as children effect how sensitive we are, if at all to these allergens.

Respiratory Physiology

The mechanics of breathing are relatively simple. Our diaphragm and intercostals contract in such a way as to cause a drop in pressure in the thoracic cavity (chest region). This drop in pressure draws air into our lungs.

A healthy airway compared to a constricted, inflamed airway.

The respiratory tract is split into upper and lower segments. The upper aspect, consisting of the nasal cavity and trachea, are primarily responsible for warming, moistening and filtering the air so that diffusion of oxygen from the lungs and more specifically the alveoli (lower aspect) into the bloodstream is maximised.

When exercising, the demand for oxygen increases, as does the need to remove carbon dioxide from our bodies. Amongst others, these two stimuli force the respiratory system into action, increasing the rate and depth of breathing. During high-intensity activity, the demand for oxygen may become so great that we begin to supplement nasal breathing with inhalation through the mouth, bypassing the effects of the nasal cavity.

Inhaling cold, dry, unfiltered air can cause irritation in the lungs, leading to inflammation, mucosal secretion and constriction of the airways, thereby increasing the resistance. This can lead to wheezing, chest tightness, breathlessness and coughing and subsequently a reduction in performance. This is known as Exercise-Induced Asthma (EIA). [1]

Should athletes be concerned?

EIA occurs in 90% of asthma sufferers. However athletes who demonstrate the symptoms of asthma when competing typically suffer from a condition called Exercise-Induced Bronchospasm (EIB). Although research suggests that approximately 19% of elite athletes suffer from EIB the incidence varies depending on the sport. Figure skaters and elite winter athletes, who are exposed to cold, dry conditions during training and competition, are more susceptible and approximately one third are thought to suffer from EIB. One quarter of elite runners demonstrate EIB symptoms, with field athletes suffering less frequently (15%).

When it comes to combatting these issues there are a number of drugs of various strengths available. These include Beta-2-agonists which are classed as bronchodilators (which widen the airways) and corticosteroids (anti-inflammatories). It is rare for one symptom to occur without the other so generally speaking, combinations of these drugs are used in tandem. The IOC rules governing the legality of these drugs have been somewhat tightened in recent years due to a growing number of athletes feigning EIB to improve their breathing capacity illegally.

Respiratory symptoms are no longer sufficient to diagnose an athlete with EIB. It is recommended that all athletes considering taking any asthma-related medication seek a clear diagnosis from a physician or respiratory specialist.

Athletes must now undergo bronchial provocation tests designed to simulate the effects of exercise. Eucapnic Voluntary Hyperpnea (EVH) is one such method and is considered the ‘Gold Standard’. The EVH challenge consists of breathing cold, dry air in and out as fast as possible for 6 minutes. Pre- and post-exercise spirometry measures are carried out and their differences calculated. Spirometry measures involve forced expiratory volume in one second (FEV1). A reduction in FEV1 by 10% post EVH can indicate EIB, although this can vary from person to person. 

It is not required that athletes inform any anti-doping organisation of medication through a declaration of use form. However athletes are advised to keep a log of what they take and when as at the time of testing athletes need to declare what they have used in the week prior. Further information can be found at WADA [2].

Advice from a legend

There are many Olympic athletes that perform at the highest level despite suffering from EIA or EIB. Marathon world record holder Paula Radcliffeis one such sufferer.

“If you learn to manage your asthma and take the correct medication there’s no reason why you shouldn’t be the best.

Marathon runner Paula Radcliffe has suffered from asthma all her life.

“I have exercise-induced asthma, which was first recognised when I started training seriously at the age of 14.

“When training, I take my preventer inhaler first thing in the morning, and I always take my reliever inhaler before I start exercising.

“It’s very important for me to warm up gently and gradually before I compete. This ensures that my asthma doesn’t interfere with my training.

“The message I always try to communicate is: control your asthma, don’t let it control you.”


 

[1] More information on asthma in sport can be found at:

https://www.sportasthma.co.uk/index.html

[2] WADA – Medical Information to Support the Decisions of Therapeutic Use Exemption in relation to Asthma:

https://www.wada-ama.org/Documents/Science_Medicine/Medical_info_to_support_TUECs/WADA_Medical_info_Asthma_4.0_EN.pdf

Other Resources:

https://www.sign.ac.uk/pdf/qrg101.pdf

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First published on: 25 July, 2012 12:00 am

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