Why does Exercise Cause Asthma Attacks?
July 5th, 2011 | 
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No one knows the exact mechanism by which exercise triggers asthma attacks. It seems to be involved nerve endings that control muscles and glands of the airways and changes in the distribution of blood flow through the lungs.
One of the most accepted hypothesis is this: When we exercise, breathing becomes faster and deeper and this, in turn:
- Increases evaporation from the surface of the lining of the airways, causing an increase in the concentration of solutes in the cellular environments. This is known as increased osmotic load.
- The airways are rapidly cooled due to heat losses produced by evaporation.
- In asthma untreated (or treated inadequately), the lining of the airways is inflamed. Moisture loss and perhaps the cooling of the lining of the airways, act as triggers and cause inflammatory cells release chemical mediators inflamed mucosa with different properties, which, among other things, cause contraction of the muscle cells of airways, causing bronchoconstriction and resulting in the typical symptoms of asthma attack.
Evidence supporting the hypothesis of the mechanism by which exercise triggers asthma attacks
The asthma attack triggered by exercise can be simulated (and provoked) voluntarily, increasing respiratory rate.
Breathing warm, moist air reduces or prevents the exercise-induced asthma. It seems that in these conditions there is less drying and cooling of the lining of the airways. As a result, there is a lower release of chemical mediators and there are fewer and fewer symptoms of bronchial asthma.
Conversely, if you breathe cold, dry air increases the exercise-induced asthma. The drying and cooling of the lining of the airways produce a greater release of chemical mediators that cause bronchoconstriction and symptoms typical of asthma.
credit to: Dr. Joaquín Muñiz Girón, Dr. Nicola Wilson
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