Exercise is a trigger for the majority of people with asthma and for some people without underlying asthma. There are a number of ways that exercise triggers asthma symptoms: water loss in the lungs, cold air, and rapid breathing, as well as allergens, irritants, and pollution during outdoor exercise.

An exercise challenge test is designed to trigger water loss in the lungs and is usually done to confirm exercise-induced asthma. If an exercise challenge cannot be performed, indirect challenges can be done instead.

How is the exercise challenge done?

Laboratory tests on a treadmill or stationary bicycle are the preferred way to do an exercise challenge. Air temperature and humidity can be controlled in the laboratory. However, the exercise challenge can also be done after a free run or other activity that caused symptoms previously.

Heart rate is used to estimate exercise intensity. In the laboratory, this can be measured with an electrocardiograph or pulse oximeter. The goal is to get your heart rate up to about 80% of your maximum for 4 to 6 minutes. Some laboratories use more precise ways to measure exercise intensity by how hard you are breathing.

You will be asked to do spirometry before exercising to get a starting FEV1. After exercising, you will repeat spirometry every 5 minutes for 20 to 30 minutes. Usually, FEV1 is lowest 5 to 10 minutes after you stop exercising. The airways generally open up again, and symptoms go away 20 to 30 minutes later. If your airways do not recover on their own within 30 minutes or you are feeling breathless, you will be given rescue medications.

An alternative to spirometry is measuring PEF (peak expiratory flow) before and after exercising. Because a peak flow meter is portable, it can be used in the environment that caused symptoms. However, this test is less reliable than spirometry.

What do the results of the exercise challenge mean?

An FEV1 decrease of 10% or more after exercising indicates exercise-induced asthma.

How do I prepare for an exercise challenge?

Wear running shoes and comfortable clothing to the laboratory. Do not eat a heavy meal before the test, and avoid vigorous exercise in the 4 hours prior to the test. Medications that make your airways less responsive should not be taken before an exercise challenge or an indirect challenge. Your provider will tell you which medications to stop and how long to stop them before the test.