There is great debate among the medical community on the issue of "Exercise-Induced Asthma". This is a type of asthma attack that occurs at a particular time; namely, during or after exercise. Some physicians insist that exercise-induced asthma does not exist and is simply a by-product of the sufferer being unfit - and this attitude extends to the general populace.
In reality, exercise-induced asthma is a very real problem that can effect thousands of people every year. It occurs when someone who already has asthma undergoes any kind of physical activity. Asthma is caused by an irritation in the tubes of the lungs, and studies have shown that the faster an asthma sufferer breathes, the more likely it is they will suffer from the traditional symptoms such as wheezing or coughing.
When we exercise, we get out of breath. This is a natural by-product of exercise and applies to even the fittest, Olympic-standard of athletes. If someone with asthma gets out of breath and begins to breathe faster, this can indeed trigger an asthma attack, as the tubes of their lungs become inflamed due to the speed of breathing.
However, there is no such thing as exercise-induced asthma without an existing asthma condition. Exercise does not create asthma; it merely worsens an existing problem. If someone is claiming to only suffer asthma when they exercise and at no other time in their life, then it is most likely that they are simply not quite fit enough to undertake the physical activity they have engaged in!