Knowledge
Hard training makes the lower airways narrow in some people, typically in the minutes after the effort rather than during it. It is one of the most common causes of exercise-related breathlessness, it is treatable, and it can be measured. But it cannot be diagnosed from symptoms alone, and that is where most of the errors happen.
Exercise-induced asthma, in clinical language exercise-induced bronchoconstriction (EIB), is a transient narrowing of the lower airways brought on by physical exertion. During hard training you breathe far more air than at rest, and mostly through the mouth, so the air reaches the airways less warmed and less humidified than usual. The airway lining loses water and heat, and that sets off the reaction that contracts the smooth muscle around the bronchi. Exactly how is not settled. The two prevailing explanations are the drying of the lining and the rapid rewarming afterwards, and they are not mutually exclusive.
It follows that the conditions matter as much as the effort. Cold and dry air, chlorinated air in swimming pools, polluted air and high pollen counts all make it worse, which is why the condition is so common in endurance, winter and swimming sports.
An important distinction: most people with asthma get worse on exertion, so for them this is one expression of the disease. But exercise-induced narrowing also occurs in people who have no other features of asthma, and that is seen particularly among athletes. Which of the two situations applies changes how the treatment is put together.
Symptoms
The timing is the most telling feature. Symptoms typically build during the effort or in the minutes right after it, peak once you have stopped, and then subside on their own over half an hour to an hour.
Some people never wheeze and never feel short of breath. The only thing they notice is a cough that arrives reliably after exercise, and it is easily put down to fitness, a cold or the weather. It is one of the most common reasons the condition goes unrecognised, particularly in children and adolescents. In rowers, “regatta cough” can be a sign of asthma.
Anyone with asthma can experience it, and so can people who have never been given an asthma diagnosis. Among athletes it is most frequent where the ventilation is high and sustained, and where the air is cold, dry or chlorinated: cross-country skiing, running, cycling, triathlon, rowing, swimming and winter sports. Team sports with repeated high-intensity efforts belong on the list too.
Allergy, hay fever and nasal congestion make it more likely, and they make it worse when they are active. The same goes for a recent airway infection. For that reason a work-up looks at the nose and at allergy as well, not only at the lungs.
This is the single most important point on the page. What people report about their breathing during exercise agrees poorly with what objective testing shows, and it fails in both directions. Some are treated for asthma for years without having it, because breathlessness during training was taken as proof. Others have a measurable narrowing without ever having thought of it as anything other than being out of shape.
Both errors carry a cost. Treatment that does not work leaves the real cause unaddressed, and for competitive athletes it also means medication on the anti-doping record without a documented reason for it. An untreated condition, on the other hand, quietly limits training and often ends up limiting the choice of sport.
The conclusion is straightforward: the diagnosis is made with measurement, not with judgement, and that is true whether the answer turns out to be yes or no.
The examinations
Which examinations are used depends on your history, your sport and what the question actually is. Lung function at rest is often completely normal in exercise-induced asthma, so a normal spirometry does not settle anything on its own.
The baseline measurement of how much and how fast you can move air, repeated after a bronchodilator. It establishes the starting point and can show asthma that is present at rest.
A simple breath test measuring nitric oxide in exhaled air as a marker of a particular type of airway inflammation. It supports the overall picture but neither confirms nor rules out exercise-induced narrowing on its own.
The airways are provoked in a way that imitates hard training: either eucapnic voluntary hyperventilation (EVH) with a dry gas mixture, or a standardised exercise test. Lung function is then measured repeatedly to see whether a narrowing develops. This is the approach normally used in athletes.
Two other provocation tests with different properties. Mannitol works through the same water-loss mechanism as exercise; methacholine acts directly on the airway muscle and is strongest for ruling asthma out, while it performs markedly worse in athletes. The choice depends on the question being asked.
Allergy testing, by skin-prick test or specific IgE, often belongs alongside these, because untreated allergy and nasal symptoms make exercise-induced asthma harder to control.
Treatment
Correctly diagnosed, exercise-induced asthma usually responds well to treatment. The plan is put together from the underlying condition, your sport and the conditions you train in, and it starts with the diagnosis being right.
Where asthma is present, inhaled anti-inflammatory treatment is the foundation. It works over weeks rather than minutes, and it is what reduces the tendency to narrow in the first place, rather than just relieving it afterwards.
Short-acting bronchodilator taken before training can prevent or reduce the narrowing. It works well, but daily use over long periods can reduce the effect, which is one reason the underlying treatment matters. Dosing is decided individually. If you have asthma, reliever medication on its own is not a treatment. Needing it before every session is a sign that the underlying treatment should be adjusted, not that you should take more of it.
A structured warm-up before the hard work often reduces symptoms, because the airways react less for a period afterwards. That effect is well documented but time-limited. Covering the mouth in cold weather works differently: it warms and humidifies the air before it reaches the airways. And adjusting when and where you train in high pollen or heavy traffic simply removes part of the exposure.
Treating allergy and nasal congestion makes a real difference, since air that passes through a blocked nose is neither warmed nor humidified properly. And inhaler technique is worth checking every time: medication that does not reach the airways cannot work.
For competitive athletes, asthma treatment has to both work and comply with the anti-doping rules. Some medicines are permitted within set limits, others require a therapeutic use exemption (TUE), and every application rests on an objectively documented diagnosis. The binding decisions sit with Anti Doping Danmark and your federation.
And if the tests come back negative, that is information rather than a dead end. Breathlessness in sport also arises from exercise-induced laryngeal obstruction (EILO), from dysfunctional breathing, and from causes outside the airways altogether. Each calls for its own approach, which is why the work-up looks at the whole picture rather than stopping at asthma.
Mannitol, methacholine, EVH and a cycle-ergometer exercise challenge in one place. What each test measures, what the answer means, and what it does not mean.
One of several possible causes of breathlessness in sport, and one that sits in the larynx rather than the lungs. On symptoms, who is affected, how the diagnosis is made with CLE, and what can be done.
Selected references behind this page.
FAQ
Not quite. Most people with asthma get worse on exertion, so for them exercise-induced asthma is one expression of the disease. But you can also have exercise-induced narrowing without having asthma otherwise, and that is seen particularly in athletes. The distinction matters for how the treatment is put together.
Because the narrowing is bound up with the airways losing water and heat during heavy breathing. The reaction builds up and is typically strongest a few minutes after the effort has stopped, after which it subsides on its own over half an hour to an hour. The underlying mechanism itself is not yet settled.
Yes. A cough after training can be the only thing you notice, with neither wheeze nor obvious breathlessness. It is a well-known reason the condition is overlooked, particularly in children and adolescents.
No. Symptoms during and after exercise agree poorly with what objective testing shows, and it fails in both directions: some have symptoms without having exercise-induced asthma, and others have the condition without having noticed it. The diagnosis is therefore made by measurement, not by judgement.
EVH stands for eucapnic voluntary hyperventilation. You breathe hard for a few minutes with a dry gas mixture, which imitates the load hard training puts on the airways. Lung function is then measured repeatedly to see whether a narrowing develops. It is one of the examinations used in athletes.
No. The purpose of assessment and treatment is the opposite: that you can train at the level you want without your breathing setting the limit. Well-treated exercise-induced asthma is not a barrier to either exercise or competitive sport.
Some asthma medicines are permitted within set limits, others require an exemption (TUE). The rules change, and the binding decisions sit with Anti Doping Danmark and your federation. The clinic can supply the objective documentation an application rests on. See the page on asthma medication and anti-doping.
Then that is important information, not a dead end. Breathlessness in sport has several possible causes, among them exercise-induced laryngeal obstruction (EILO) and dysfunctional breathing, and each calls for its own approach. A negative asthma test moves the work-up forward rather than ending it.
As a rule, yes. Well-controlled asthma matters for both you and the baby, and most inhaled treatments are continued during pregnancy. Never stop your preventer medication on your own. Talk to us or to your GP, so the plan can be adjusted.
The clinic assesses exercise-related breathlessness with objective testing, and asthma in athletes is one of its areas of special expertise. A referral from your GP is normally required; you can also be seen as a private or insurance patient. This page is general information and does not replace a medical assessment.