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Exercise-induced asthma

Why does it happen? What can you do about it?

 


 

 

Introduction

A few people seem to get asthma attacks only when they run or take other exercise. Doctors used to think this was a separate form of asthma. But it is very usual for people with asthma to have this happen to them. This 'exercise-induced asthma' is especially a problem for young people. In fact doctors used to puzzle over why children got exercise-induced asthma and why adults did not. Eventually research discovered the reason; adults don't take nearly so much exercise! We now think that people who get asthma attacks only when they take exercise just have asthma which is too mild to show up most of the time, needing the extra provocation from faster breathing to bring it out.

 

Exercise is just one of many things which show that the air passages are irritable in asthma

If you have asthma, your air passages are irritable. This means things which are harmless to other people may trigger an attack of asthma. So you might get asthma from:

  • Cold air, if you move from warm indoor air to cold air outdoors.

  • Tobacco smoke, e.g. in a pub.

  • Emotional stress. Although there seems to be no really good research on this, people with asthma often say their asthma gets worse if they are upset.

  • Infections of the lining of the breathing passages, such as colds and 'flu.

  • Some drugs, especially medicines called beta blockers used for high blood pressure or heart disease.

  • Laughing. So don't laugh! (Only joking, but it can happen.)

  • Irritants in asthma inhalers. Strange, but true. Some powder inhalers can cause a small amount of chest tightness. Pressurised aerosol inhalers need to have a lubricant and this can cause worsening of air passage narrowing, occasionally bad enough to be noticeable.

  • Breathing tests. Just as the faster breathing in exercise can bring on attacks, the faster and deeper breathing you have to do for most breathing tests can bring on quite a noticeable worsening of airway narrowing in a few people.

  • Sulphur dioxide used as a preservative in soft drinks and wine. This can cause chest tightening within seconds of drinking, or even breathing the air above such a drink.

  • Indigestion, with stomach acid coming up into your gullet. This is called gastro-oesophageal reflux.

  • Histamine or methacholine aerosols. In specialised tests doctors use an inhaled mist of these substances to measure how irritable your air passages are. In asthma they are more irritable than normal. During allergic or asthmatic reactions cells in the lungs release histamine . Methacholine mimics the effect of a substance (acetylcholine) released by nerves in the lung during asthma. Both substances cause an asthma attack in anyone who breathes enough of them, but people who have asthma will get an attack from a much smaller amount. In the test, the amount of asthma produced is small and very bearable, and it wears off quickly. The result gives us a measurement which can be very useful.

To some extent people differ in which of these things cause the most asthma. Nevertheless, they all reflect the irritability of the air passages in asthma, even if some of them do so in somewhat different ways.

So exercise is just one of many things which can provoke narrowing of the air passages in asthma. It is just one of many things which reveal the abnormal irritability or 'twitchiness' of the air tubes which is an important feature of asthma. The medical term for this 'twitchiness' is 'hyperreactivity'.

 

Are some kinds of exercise worse than others?

Yes.

If you take different kinds of exercise so that you use the same amount of oxygen in each one, some will cause more wheeziness or chest tightness than others. Running outdoors will in general be worse than swimming. In fact swimming is one of the best forms of exercise for people with asthma because it usually causes the least amount of chest tightness. Running indoors on a treadmill, or cycling on an indoor exercise bike will come somewhere between outdoor running and swimming.

Other factors influence the amount of worsening of your breathing which you get from a particular form of exercise. Generally for example, if the air you breathe is cold and dry, the asthma will be worse. If it is warm and moist, the asthma will be less bad. This explains why swimming generally causes less asthma than outdoor running.

Some people get worsening of their asthma from the chlorine fumes from swimming baths. This is another factor which can affect the result, and for such people swimming in a chlorinated pool is much worse than running.

The timing of the exercise is important. It takes about six minutes of exercising to bring on exercise-induced asthma, and exercising for quite a bit less than this may not do it.

For a few hours after you have had exercise induced asthma, repeating the same amount of exercise will no longer produce the same amount of asthma symptoms, or may produce none at all.

So you may be able to 'run through' your exercise induced asthma either by warming up with short bursts of exercise, or by continuous exercise which does not bring on a severe attack. Sports and exercises which consist of short bursts of activity with periods of rest in between can be particularly suitable for people with asthma. Examples include relay races, and team sports in which you are not running all the time.

There is also persuasive evidence that gradual athletic training can make you less prone to exercise-induced asthma. At a special school for children with asthma near Oslo in Norway, children ended up being able to do far larger amounts of exercise than they could tolerate before a physical training programme. Although some of this improvement may well have been due to the excellent medical care they received, the doctor in charge thought that the exercise training itself played a vital part in the improvement.

In fact better treatment with medicines can have a powerful effect on exercise-induced asthma. The better your asthma control, the less you will be troubled by exercise-induced asthma.

Exercise-induced asthma is an excellent example of a problem which you can begin to solve once you understand it better.

 

What is it about exercise that makes asthma worse?

The last time I read this up, the evidence was that increased breathing during exercise causes cooling and drying of the lining of the air passages and that these are necessary for someone to get exercise-induced asthma. This explains why warm moist air protects against exercise-induced asthma.

Nobody knows exactly why the drying and cooling of the airway linings causes the asthma episode.

 

Exercise-induced asthma can be useful!

Well, of course you would rather not have asthma of any kind, however 'useful'. But seriously, exercise-induced asthma can be useful for diagnosing asthma in a child. Exercising a child for about 6 minutes is a convenient and safe way of provoking a mild asthma attack, and this has led to many children getting early and appropriate advice and treatment. We can exploit this feature of asthma to help defeat asthma.

Exercise-induced asthma has also been useful in asthma research. It can be used for testing medicines which may help asthma.

 

Athletes and exercise-induced asthma.

A lot of athletes, especially skiers and runners, get exercise-induced asthma. This may be partly because an amount of asthma which does not matter to most people can mean the difference between winning and losing to an athlete. So it may simply be that athletes notice the condition when other people overlook it. The other reason may be that the same underlying disease process goes unnoticed in non-athletes because they simply never exercise to the degree athletes do.

If you are an athlete and have this problem it is worth getting top-level specialist expertise to help you solve it. Just as you train to levels of fitness which ordinary people don't even think about, so it is worth getting the best advice to help you break the barrier which poorly treated exercise asthma can pose. Many Olympic gold medal winners have been asthmatic and have suffered from exercise-induced asthma. With the right help and self-discipline the problem can often be overcome.

 

Should people with asthma avoid exercise?

No, definitely not. In fact enjoyable exercise is even more important for someone with asthma than for other people.

Children with asthma have in the past often been asked to sit on the sidelines whilst their classmates played games and did sports. This is completely wrong if there is any reasonable way in which the child can be made fit enough to take part. What is true for children is also true for adults.

Asthma attacks are hard work. One of the dangers in an asthma attack is fatigue, which may make you weaken in your fight to breathe. Obviously it is good to have strong breathing muscles, because strong muscles tire less easily. Obviously the way to get strong breathing muscles is to take exercise. Far from being prevented from getting exercise, people with asthma should take as much exercise as they can enjoyably manage. With care and understanding this will be much more than most outsiders think possible. Good medications and intelligent use of the tricks for getting round the problem of exercise-induced asthma can achieve tremendous results.

 

What can I do about exercise-induced asthma?

You will already have picked up some useful clues. Swimming rather than running, warmer and moister air, warm-up by short periods of exercise, and getting into training can all help.

In Scandinavia cross-country skiers sometimes wear breathing masks which store the heat and moisture from the air they breathe out and then return it to the air they breathe in. This is helpful in avoiding exercise-induced asthma.

Good control of your asthma, whether by breathing in a 'preventer' treatment or by avoiding causes of asthma such as house dust mites and pets can have a tremendously helpful effect on exercise-induced asthma.

Reliever inhalers can be tremendously helpful if you use them just before you exercise. This applies especially to the so-called 'beta-2 stimulants' such as salbutamol (albuterol) or terbutaline. The benefit should last for hours.

Long-acting reliever inhalers are also very helpful; they just work for longer.

If you are a competitive athlete or sportsman, you may be concerned about disqualification because you use drugs. The good news is that all the ordinary asthma medicines, used in the medically recommended way and dosage, are acceptable to sporting bodies provided you use them correctly for asthma. The wise thing is to check with your sports authority or sports doctor.

 

 



This page is maintained by Martin Stern
This page published on 23 & 24 March 1998. Style edited 10 Feb 2000.

Copyright © 1998 Martin Stern