Understanding Your COPD Better By Using These Exercise Tests
Exercise tests are an effective way to not only measure physical strength and endurance, but also how well you can breathe. They can reveal vital information about your lung function, your oxygen levels, and your general physical abilities.
This can help you and any health professionals you work with better understand and treat your disease. Because of this, both doctors and fitness specialists use a variety of different exercise tests to evaluate people with COPD and other lung conditions.
Why Take an Exercise Test?
If you have COPD, your doctor might ask you to take an exercise test for a several possible reasons, including to measure how severe your symptoms are, what kind of exercise you can tolerate, and to determine what kinds of treatments can help. They are also useful for monitoring general lung function and tracking improvements or decline in your ability to exercise over time.
Exercise test results also serve as a good measure of how your disease and respiratory symptoms affect your mobility and your everyday life on a practical level. Because of this, they are especially useful for evaluating people with advanced COPD, who often suffer from shortness of breath so severe that normal daily activities become a struggle.
There are many different types of exercise tests, each designed to measure your physical and respiratory abilities in a different way. The results can be used for a variety of different purposes, including to measure COPD symptoms, to design personalized exercise programs, and to determine whether or not a patient needs supplemental oxygen therapy.
That's why, in this post, we're going to introduce you to the five most common exercise tests that medical and fitness specialists use to evaluate COPD and other respiratory diseases. We'll explain what these tests are, how they work, and what each test can tell you about your health.
With this knowledge, you'll know what to expect and how to prepare the next time your doctor wants you to complete an exercise test. Most importantly, however, this will also give you the vocabulary and the information you need to actually read your test results and understand what they mean for you.
Field Walking Tests Versus Laboratory Tests
There are two main categories of exercise tests: field walking tests and laboratory tests. Laboratory tests are usually done on a treadmill or exercise bike in a lab, while field walking tests are performed on flat ground, usually in a large, open space.
Lab exercise tests tend to be more intense because the exercise machine sets the pace and pushes you to keep moving continuously. This makes it more difficult to pause, slow down, or stop for a rest during the test.
During most field walking tests, however, you can set your own pace, pause, and take breaks as often as you need to. That's why, in many cases, field walking tests are better suited for people with chronic respiratory diseases, who often have serious physical limitations and low exercise tolerance.
Laboratory exercise tests can also get pricey because they require an exercise machine and other specialized equipment (e.g. electrocardiogram sensors). On the other hand, field walking tests can be done with minimal equipment, making them a simpler and less expensive choice.
In this post, we are going to focus mainly on field walking tests, since they are the simplest and most common types of exercise tests used for people with COPD. However, we will also discuss one lab-based test, the cardio-pulmonary exercise test, which many researchers consider the most accurate and reliable form of exercise testing.
We'll go over each test in detail so you'll know what to expect from an exercise test and how to interpret your results. We've also included some extra tips at the end of this article to help you prepare for your exercise test.
The following sections include: the 6-minute walk test, the incremental shuttle walk test, the endurance shuttle walk test, the sit-to-stand test, and the cardio-pulmonary exercise test.
The 6-Minute Walk Test
The 6-minute walk test (abbreviated 6MWT) is a simple test that measures how far you can walk in 6 minutes. This is one of the most frequent types of exercise tests used for people with COPD and other respiratory conditions.
The results give you a general idea of how well your lungs function and how much physical endurance you have. This can be used to determine how much your disease affects your ability to get around and help your doctor determine the best course of treatment.
6-minute walk tests are often done multiple times for comparison, especially before starting a new COPD medication or another type of therapy. In that case, you will take one test before beginning the treatment and another shortly after in order to see if your test results change.
How the 6-minute Walk Test Works
To complete this 6-minute walk test, you will simply walk on hard, even ground for exactly 6-minutes straight. The goal is to measure how much distance you can cover in that time without pushing yourself too hard.
Before the test, you will sit and rest for about ten minutes so the test technician can get a baseline measure of your heart rate, blood pressure, and blood oxygen saturation. Then, the technician will ask you to rate your breathlessness via a standard scale, such as the Borg scale.
The Borg scale allows you to choose from a range of numbers, one to ten, with higher numbers representing more severe shortness of breath. To use it, you simply match the symptoms you feel with the number that best describes them on the scale.
This helps you quantify your breathlessness in a consistent way that you and your doctor can use to measure changes over time. Breathlessness scales are used all the time in COPD evaluations, including regular check-ups and other types of exercise tests.
After taking down your breathlessness rating, the technician will start a stopwatch timer and have you begin walking on the track. To complete the test, all you have to do is continue walking until the timer reaches six minutes.
You should try to walk as far as you can, but you may pause for breath or stop walking any time you need to. However, the timer will keep running and any rests you take will affect your test results.
During the test you may also use supplemental oxygen, if you're prescribed it, and any walking aids (such as a cane or walker) that you normally use to get around. Just make sure to bring the same aids for future exercise tests so your results will be consistent.
Let the technician know if you feel too exhausted to finish or experience any severe or dangerous symptoms. Intolerable shortness of breath, chest pain, and leg pain are all urgent indications that you should stop the test.
When you make it to the six minute mark, the walking part of the test will be over and you can sit down to rest. The technician will record the total number of laps you completed, ask you to rate your breathlessness again, and record your heart rate, blood pressure, and blood oxygen saturation once more.
What the Results of Your 6-Minute Walk Test Mean
The results of the 6-minute walk test reflect your general respiratory health and give you a baseline measure of your physical ability. The primary result of the test is your 6-minute walk distance (abbreviated 6MWD).
Interpreting Your 6-minute Walk Distance Score
A longer 6MWD indicates better exercise tolerance and better lung function, while shorter distances indicate poorer exercise tolerance and lung function decline. Research shows that you need to increase your distance by about thirty meters (about 98 feet) in order to determine that you've made a significant improvement.
You can also compare your 6-minute walk distance to standard reference values in order to see how your results compare to healthy people of your age, sex, weight, and height. Your doctor may provide you with a table of reference values, or you can plug your 6MWD into this online calculator.
Since walking is a light and simple activity that's part of normal living, the 6-minute walk distance is considered an excellent measure of how much your disease affects your everyday life. Studies show that short distances (especially distances less than 150 meters) are associated with more severe respiratory disease, more severe mobility limitations, and a higher risk of death.
Interpreting Your Breathlessness Scores
Your breathlessness scores are also important, because they specifically measure how severe your COPD symptoms are and how they change in response to light physical activity. If there is little change in your breathlessness score throughout the test, this indicates that you tolerate exercise relatively well.
On the other hand, a significant increase in breathlessness indicates that light physical activity puts a lot of strain on your lungs. This is a sign of low exercise tolerance and more advanced COPD.
Interpreting Your Heart Rate Measurements
In general, the lower your resting heart rate is, the better your cardiovascular fitness. That's because your heart rate is a good indication of how hard your heart has to strain in order to do it's job.
A lower heart rate means that your heart can pump your blood effectively with fewer beats. This usually indicates better exercise tolerance and better physical endurance.
A faster heart rate means that your heart has to work harder in order to pump enough blood around your body to meet your body's needs. This indicates low cardiovascular fitness and lower exercise tolerance.
A fast resting heart rate can also be a sign of other health conditions, including high blood pressure and narrowed arteries caused by cardiovascular disease. It can also indicate that your blood oxygen levels are low, which can be caused by poor lung function.
Low blood oxygen levels force your heart to pump blood faster, which often resulting in a higher resting heart rate. As a result, your heart rate and blood oxygen saturation readings can help your doctor determine how well your lungs are working.
Studies even show that resting heart rate can reliably predict the severity of a person's COPD. Higher resting heart rates are associated with more advanced COPD and a higher risk of death from the disease.
Interpreting Your Oxygen Saturation Reading
Another important measure is your blood oxygen saturation readings, which are usually recorded before, after, and sometimes during the test. This number is usually written as your SpO2%, and it can tell you if, and to what degree, basic exercise causes your oxygen levels to drop.
When your blood oxygen saturation falls to low—below 95%--it is known as hypoxemia, a potentially dangerous condition that requires treatment (often with supplemental oxygen therapy) to correct. This happens when your lungs can't absorb enough oxygen to supply your body with the full amount that it needs.
Some people with COPD experience chronic hypoxemia, meaning their blood oxygen levels tend to be too low most of the time. Hypoxemia tends to get more severe as COPD progresses, and the severity of hypoxemia is a good indication of how advanced your COPD is.
Blood oxygen saturation readings are also the main determining factor when deciding whether or not someone needs to use supplemental oxygen. In most cases, people with COPD and other chronic respiratory diseases begin supplemental oxygen therapy when their oxygen levels fall below about 90%.
However, some people with COPD only experience low blood oxygen saturation when they exercise, a condition commonly referred to as exercise-induced oxygen de-saturation. This can be difficult to catch during normal check-ups and exams, since it only occurs during physical activity.
Because of this, exercise tests like the 6-minute walk test (and especially the incremental shuttle walk test, which we'll discuss next) are useful for catching exercise-induced hypoxemia in people with respiratory diseases. By recording your oxygen saturation levels at different points during the test, it can reveal whether or not exercise causes them to drop.
Putting it All Together
All of this information helps your doctor determine how severe your symptoms are and make a more accurate prognosis for your disease. For instance, a variety of studies have shown that, in general, lower 6MWT scores in people with COPD are associated with a higher risk for hospitalization or death.
This isn't surprising, since studies have long shown that physical activity and exercise are vital for maintaining health, breathing efficiency, and physical mobility in people with COPD. Because of this, exercise capacity is generally a pretty good predictor of how advanced the disease is and what kinds of outcomes you can expect.
In many cases, however, the primary purpose of the 6-minute walk test is to establish a baseline to compare future 6MWT results against. Then, repeat tests will reveal how your endurance, which is representative of your overall lung function, improves or declines over time.
The Incremental Shuttle Walk Test
The incremental shuttle walk test (abbreviated ISWT) is another walking exercise used to measure both lung function and physical endurance. However, the ISWT is slightly more challenging than the 6-minute walk test because it pushes you to walk more quickly and for a longer period of time.
The goal of the ISWT is to see how many times you can walk up and down a short track while steadily increasing your speed. You'll be supervised by a technician who will record basic data about your heart rate, oxygen levels, and breathing symptoms at regular intervals during the test.
The goal of the test is to measure your lung function as you progressively work up to your maximum exercise capacity. This gives you a solid measure of your endurance and how your oxygen levels change as you increase your exercise intensity.
Like the 6-minute walk test, you may need to take the ISWT on more than one occasion in order to see if the results change. This is particularly useful for measuring whether or not a new medication, exercise program, or other treatment is helping you or not.
How the Incremental Shuttle Walk Test Works
To take an incremental shuttle walk test, you will walk on a course made up of two cones placed about thirty feet apart on hard, flat ground. The full path you walk from cone to cone is exactly ten meters (or about 32 feet) in length.
Each time you complete a trip from one cone to another, you've finished a single increment, or shuttle. When you take the test, you will complete multiple shuttles one after the other at gradually increasing speeds.
Before the test, your doctor will tell you when and if you should use your bronchodilator and other medications on the testing day. To be safe, you should always bring your bronchodilator medication, your supplemental oxygen (if you use it), and any walking aids you normally use.
In order to keep the test consistent, incremental shuttle walk tests are always led by a tape of recorded audio instructions. Although you will have a test technician to help you, the recording will be your main source of instruction throughout the test; it will tell you exactly when to start and set your walking pace.
As you walk, the recording will play tones (or beeps) in a steady rhythm to match the beat of your steps. To complete each shuttle, you will walk in time with recording, taking one step each time you hear a beep.
The tones will play slowly at first but speed up slightly every minute, forcing you to increase your walking pace gradually throughout the test. The recording is also timed so that you have to complete each full shuttle in a specific amount of time before an end tone plays.
As you walk, the technician running your test will record several physical measures at regular intervals, including your heart rate (in beats per minute), your blood oxygen saturation (written as SpO2 %), and what degree of breathlessness you experience. You may stop the test at any time if it becomes too difficult to breathe or if you get too exhausted to continue.
The incremental shuttle walking test ends when you can no longer go on or when you can no longer keep up with the pace set by the recording. Once you finish, the technician will immediately record your blood oxygen saturation, heart rate, and breathing symptoms again.
Then, after you've had two minutes to rest, the technician will take all these measurements one final time. He will also record the final number of shuttles you walked and your reason for stopping the test.
Check out this video to see an example of how an actual incremental shuttle walk test is performed.
What the Results of Your Incremental Shuttle Walk Test Mean
At the end of your incremental shuttle walk test, the results will show your SpO2, heart rate, and breathlessness at each minute during the test. It will also state why you had to stop the test and the total number of shuttles you were able to complete.
These are important measures that can tell you a variety of things about your physical fitness and your overall respiratory health. Some of these measures are very similar to the ones taken during the 6-minute walk test, so we will go over them only briefly again here.
Interpreting Your Blood Oxygen Saturation Scores
As we discussed earlier in this post, your blood oxygen concentration, or SpO2, tells you how much oxygen is in your blood. This indicates how well your lungs are functioning; an SpO2 above 95% is considered normal, while anything less indicates that you have hypoxemia.
One of the most important things an incremental shuttle walk test can reveal is how your blood oxygen saturation changes throughout the course of the test. This can reveal whether or not you experience exercise-induced hypoxemia and help your doctor determine the best way to treat it.
Compared to the 6-minute walk test, the ISWT is generally more intense, so it allows you to see how your oxygen saturation levels respond to heavier amounts of exercise. It also gives you a wider range of data points to analyze, since it measures your oxygen levels at regular intervals from rest all the way up to your maximum pace.
Interpreting Your Breathlessness Scores