Exercise-Induced Asthma: Definition, Causes and Treatment
Exercise-Induced Asthma: Definition
Exercise-induced asthma is defined as a type of asthma attack that is
triggered by doing sports or physical activity. During such an asthma exacerbation, airways are
constricted, and there is a limited flow of air to the lungs with all 3
classical signs of asthma: bronchoconstriciton, inflammation of airways, and excessive
production of mucus.
As a result of these factors, gas exchange between outer
air and the alveoli in the lungs is limited. The person feels air hunger (of
self-suffocation) and is often in a state of panic or anxiety during or
immediately after running, swimming, cycling, and other forms of physical
Note that, during initial stages of asthma, CO2 levels in the blood
becomes too low. This reduces brain and body oxygenation. For later stages
(COPD), the lungs are damaged and brain and body O2 levels become even
lower, in spite of too high arterial CO2. Even most medical doctors do not
understand this simple effect.
Causes of exercise-induced asthma
There are 4 significant changes in the respiratory system that take place
due to exercise in comparison with quiet breathing at rest. These changes
are shown on the chart.
Note that normal breathing at rest is very small and slow: only 6 L/min
at rest with 10-12 breaths per min for the respiratory frequency.
During physical exercise, most normal people can breathe more than 100 L/min.
This causes increased mechanical stress (shear stress) on airways due to
movements of large volumes of air.
However, the key triggering factors of
sports induced asthma relate to
losses in alveolar CO2 (CO2 content in the airways). Since CO2 is a powerful
relaxant of smooth muscles, mouth breathing during exercise leads to alveolar
hypocapnia (CO2 deficiency) causing bronchoconstriction (see the links below
for medical research in this area). Overbreathing and low CO2 are key causes of asthma.
Treatment for sport induced asthma
Indeed, those medical studies that compared the
effects of mouth and nose breathing found that nose breathing
during exercise provides definite benefits for people with bronchial asthma during
exercise with less or no bronchospasm involved (Shturman-Ellstein, 1978;
Mangla & Menon, 1981 - see abstracts of these studies below).
breathing produces the following effects on the respiratory system during
- higher levels of CO2 in the airways causing bronchodilation and reduced
- warming of air in the sinuses and prevention of overcooling of airways
- humidification of the incoming air flow in the sinuses and prevention of
drying of airways that is very important for people with asthma
- greatly reduced friction in airways due to hypercapnic bronchodilation and reduced
- increased levels of nasal nitric oxide absorbed in the lungs and blood
- greater increase in body-oxygen levels after exercise (this can be checked next morning using the body-oxygen test).
- greater training effect (larger increase in VO2max), faster adaptation to
higher intensity of training, and faster recovery from injuries.
The only disadvantage of nose breathing is that relatively unfit people
are usually not able to run or exercise rigorously due to their low body oxygen
content at rest caused by heavy or deep breathing. This relates to many
asthmatics. Let us consider how. While normal breathing at rest is only 6
L/min for a 70-kg man, asthmatics breathe about 12-15 L/min.
Chronic hyperventilation causes low body-oxygen levels 24/7, the
hypersensitive immune system (with possible development of new allergies), bronchospasm, and chronic inflammation of
airways leading to major asthma symptoms.
to the clinical experience of more than 180 Russian medical doctors teaching the
Buteyko breathing technique, physical exercise with nose breathing is the
most natural and most effective method to increase body oxygenation and
eliminate hyperventilation naturally. However, these MDs also found that most
people with asthma should start with low intensity exercise (e.g., walking or fast
walking) with nose breathing only to prevent destruction of airways during asthma exacerbation. The patients need to increase their
body-oxygen levels up to 20 seconds or more in order to exercise rigorously
with nose breathing only. In most cases, this may take up to 2-3 weeks. These doctors observed complete clinical remission (with normal lung function results) or asthma cure in thousands of their patients.
Therefore, nose breathing during exercise is an excellent method and
therapy to eliminate exercise induced asthma, reduce medication, prevent exercise-induced
asthma, achieve greater improvements in sports performance, and increase body-oxygen levels.
References (with abstracts)
Shturman-Ellstein R, Zeballos RJ, Buckley JM, Souhrada JF, The
beneficial effect of nasal breathing on exercise-induced bronchoconstriction,
American Review of Respiratory Diseases 1978 Jul; 118(1): 65-73.
In the first step of a study of the relation of nasal and oral breathing
during moderate treadmill exercise to the onset of bronchoconstriction in
young patients with perennial bronchial asthma, it was observed that most
subjects spontaneously breathed with their mouths open when instructed to
breathe "naturally." Subsequently, when they were required to breathe only
through the nose during the exercise, an almost complete inhibition of the
postexercise bronchoconstrictive airway response was demonstrated. When
instructed to breathe only through the mouth during exercise, an increased
bronchoconstrictive airway response occurred, as measured by spirometry,
flow-volume relationships, and body plethysmography...
Mangla PK, Menon MP, Effect of nasal and oral breathing on
exercise-induced asthma, Clinical Allergy. 1981 Sep; 11(5): 433-9.
The effect of nasal as well as oral breathing during level-ground running
for 6 min on the post exercise bronchial response was studied in fifteen
people (five asthmatics with exercise liability, five asthmatics with no
such liability and five normals). Each patient did the exercise twice; once
with the nose clipped and once with the mouth closed. FEV1 was measured
before exercise, immediately after exercise and at 5, 10, 15, 20 and 30 min
thereafter. A fall in FEV1 of 20% or more from the basal level was taken as
evidence of bronchoconstriction. When the patients were required to breath
only through the nose during the exercise, the post-exercise
bronchoconstrictive response was markedly reduced as compared with the
response obtained by oral breathing during exercise, indicating a beneficial
effect of nasal breathing. Nasal breathing was beneficial as compared with
oral breathing in normals as well...
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