Although exercise is a common trigger for asthma symptoms, this does not mean that you should avoid exercise just because you have asthma. On the contrary, exercise has health benefits for people with asthma, as it does for most other people.
Exercise and asthma symptoms
Exercise-induced asthma symptoms are caused by exercise-induced bronchoconstriction, which is transient (short-term) airway narrowing brought on by vigorous exercise.
It is thought that exercise-induced bronchoconstriction involves loss of heat and water from the airways as they try to warm and moisten large volumes of incoming cool dry air. As the airways lose moisture and heat, they become inflamed and narrow, limiting airflow.
Asthma symptoms that are triggered by exercise include:
- chest tightness; and
- excess mucus production.
Symptoms may start during exercise but usually worsen in the 5-10 minutes after you stop exercising.
Who gets exercise-induced asthma symptoms?
If you train intensely and frequently, especially in cold dry air, your risk of developing exercise-induced bronchoconstriction increases. Other factors that make exercise-induced asthma symptoms more likely are allergens (substances that can trigger an allergic reaction, such as pollen) or irritants in the environment, and coincident respiratory infections.
Exercise-induced asthma symptoms are common in school-aged children, and many affected children won’t have asthma symptoms in situations other than exercise. However, bear in mind that asthma may not be the cause of your child’s breathlessness when they exercise — see your doctor for a proper assessment and diagnosis.
To see whether you have exercise-induced bronchoconstriction, your doctor will ask about your symptoms and their relation to exercise.
Your doctor may also suggest performing lung function tests (spirometry), including an exercise challenge test. This involves measuring your lung function before and after exercise. Sometimes instead of actually exercising, a substance is breathed in to mimic the effect that exercising has on the airways.
Exercise-induced bronchoconstriction can be diagnosed if the difference in lung function before and after exercise is more than 10 per cent in adults, and 13 per cent in children.
Exercise and asthma control
Some people get asthma symptoms only after exercise, while others find that their asthma also occurs in other situations.
The appearance of exercise-induced asthma symptoms can be one of the first signs that asthma is not well controlled. However, it is possible to have exercise-induced asthma symptoms even when asthma is well controlled.
If you or your child has asthma, don’t stop exercising; instead aim to have the best possible asthma control. Both reliever and preventer medicines can be used in the treatment of exercise-induced bronchoconstriction. Depending on how severe the asthma is, this may involve taking medicines:
- during asthma episodes only;
- just before exercise; or
- on a daily basis.
The benefits of exercise
If you have asthma, it’s worth persisting with exercise — symptoms are less easily triggered when you are fit than when you are unfit. Exercising can improve your heart and lung fitness, even though your lung function tests may not change.
It’s a good idea to start off slowly with exercise though, especially if it’s been some time since you were very active or if you’ve never exercised before. Over time you can gradually increase the intensity and duration of exercise.
Selecting the right exercise for you
According to the National Asthma Council Australia, there is insufficient evidence from clinical trials to recommend one form of physical activity over another for people with exercise-induced asthma symptoms.
Intense exercise, such as running, cycling or team sports may be more likely to trigger symptoms than less intense exercise such as golf or walking.
Swimming can be a mixed blessing — the warm humid air might reduce the risk of exercise-induced bronchoconstriction, but some people find their airways react to the chlorine in indoor pools.
Tips for avoiding asthma symptoms when you exercise
The National Asthma Council Australia advises the following strategies to help manage the symptoms of exercise-induced bronchoconstriction.
- Warm up before you exercise.
- Keep as fit as possible.
- Exercise in an environment that is warm and humid.
- Avoid exercising in environments where the air contains a lot of allergens or irritants.
- Try to breathe through the nose or consider using a mask.
- Do some cooling down exercises after strenuous exercise.