Metabolic Exercise Stress Test

A metabolic exercise stress test, also called a cardiopulmonary exercise test (CPET), measures how your lungs and heart respond to physical activity. The test measures the levels of oxygen and carbon dioxide in your blood and shows how much air your lungs can take in. It’s valuable for people with heart failure, COPD and many other conditions.


What is a metabolic exercise stress test?

A metabolic exercise stress test involves exercising on a bike or treadmill while a healthcare provider monitors you. It’s the gold standard for checking your cardiorespiratory fitness (CRF). CRF refers to how well your heart, lungs and blood vessels can send oxygen to your muscles during physical activity.

You may hear your healthcare provider call this test a cardiopulmonary exercise test (CPET). That’s because it evaluates your heart (cardio) and lung (pulmonary) function at the same time. This test helps providers diagnose and treat a range of conditions, including heart failure and chronic obstructive pulmonary disease (COPD). It also helps providers determine your prognosis, or expected outlook, as you live with one or more chronic conditions.

Important: If you have a pacemaker or defibrillator, your healthcare provider must check it before your test. Call your provider to schedule a device check.

Cardiopulmonary exercise testing vs. stress test

A metabolic (cardiopulmonary) exercise stress test evaluates your heart and your lungs. This makes it different from a stress test that your cardiologist may order to evaluate your heart. Both tests involve exercising on a bike or treadmill while lab technicians monitor you and record data. But in a metabolic stress test, you breathe through a piece of equipment (a facemask or a mouthpiece). This device measures the amount of oxygen and carbon dioxide in the air you exhale as well as how much air your lungs can take in.

You can think of a metabolic stress test as a stress test with all the bells and whistles. Your technician connects you to more equipment than in a standard stress test, and as a result, the test produces much more data. This data helps your pulmonologist, cardiologist and other providers understand how your heart and lungs respond to exercise.

What does a metabolic (cardiopulmonary) exercise stress test show?

A metabolic exercise test shows which cardiovascular diseases and/or lung diseases are limiting your ability to exercise. If you have shortness of breath or chronic fatigue, a metabolic exercise test can get to the bottom of the situation and figure out the cause.

Your provider may order this test in order to:

  • Find the cause of your exercise intolerance (why you feel short of breath or very tired during physical activity).
  • Identify how much exercise your heart and lungs can handle.
  • Diagnose cardiovascular disease and lung disease.
  • Check the severity of your condition and form a prognosis.
  • Evaluate your risk for complications before having a major surgery.
  • Guide your treatment plan.
  • See how well your body is responding to treatment.
  • Assess your progress with physical training (like cardiac rehab).
  • Help you develop a safe and effective exercise program.

Who needs a metabolic (cardiopulmonary) exercise stress test?

Your healthcare provider will determine if you need this test. In general, it’s suitable for children aged 10 and older and adults of all ages. Providers order metabolic stress testing to diagnose and manage the following conditions:

Providers also order metabolic stress testing before certain surgeries, including:

Cardiopulmonary exercise testing in heart failure

Cardiopulmonary exercise testing (CPET) is a vital tool that providers use to help people with heart failure. This test evaluates your breathing and accurately determines how much oxygen you can breathe in at a time. The data from this test shows the severity, or stage, of your heart failure and guides your treatment plan.

Who shouldn’t have a metabolic (cardiopulmonary) exercise stress test?

There are some reasons why it’s not safe for you to have this test. Healthcare providers call these reasons “contraindications.” This test may not be safe for you if you have:


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Test Details

How do I prepare for the test?

Follow your healthcare provider’s guidance on how to prepare for your metabolic exercise stress test. Below are some general guidelines.

  • Avoid all products that contain caffeine for 24 hours before the test. Caffeine will interfere with the results of your test. Caffeine is in coffee, tea, soft drinks and chocolate. There’s also a trace amount in strawberries and any product labeled as decaffeinated or caffeine-free.
  • Don’t eat or drink anything except water for four hours before the test.
  • Don’t smoke or vape for eight hours before the test (ideally, avoid it for 24 hours beforehand). Nicotine will interfere with the results of your test.

Should I take my medications the day of the test?

Ask your provider if you need to adjust your medication schedule. In general, you should avoid any over-the-counter medications that contain caffeine for 24 hours before your test. These include some diet pills, NoDoz®, Excedrin® and Anacin®.

Guidelines for people with diabetes

If you take insulin to manage your blood sugar, ask your provider what amount you should take the day of the test. Often, providers will advise you to take only half of your usual morning dose and to eat a light meal four hours before the test.

If you take pills to manage your blood sugar, wait to take your medication until the test is done.

What should I wear on the day of the test?

Wear comfortable clothes that allow you to move easily. You may also want to choose clothes that are cool (like a sleeveless tank or light cotton top) since you’ll work up a sweat. You can wear these clothes to your appointment or change once you’re there. Also, be sure to wear comfortable shoes (like athletic sneakers).

You’ll have access to a locker to store your belongings during the test. But it’s a good idea to leave any valuables at home.

How is a metabolic (cardiopulmonary) exercise test performed?

Your test will take place in a stress lab (a room where people have stress tests). A lab technician will perform the test while a physician supervises. You’ll either cycle on a stationary bike or walk on a treadmill. Cycling is the more common method. Your provider will determine the better method for you based on your age, overall health, fitness level and other factors.

While you exercise, you’ll breathe into a device that evaluates your breathing. You’ll use either a facemask or a mouthpiece, and you may be able to choose which device is more comfortable for you.

You can expect the following steps during your test:

  1. Electrocardiogram (EKG) connection: A technician places electrodes (small, flat stickers) on different areas of your chest. These electrodes connect with a monitor that charts your heart’s electrical activity during the test.
  2. Resting phase: This usually takes three minutes. Your technician helps you get comfortable with the facemask or mouthpiece, and you start breathing through it. Your technician takes baseline vital signs including your blood pressure and blood oxygen level. They also monitor your heart rhythm on the EKG monitor. If you need arterial blood gas measurements (to check oxygen and carbon dioxide levels in your blood), your technician inserts an arterial catheter. This is a small tube that goes into an artery in your arm (radial artery) and collects periodic blood samples during your test.
  3. Unloaded phase (warmup): This usually takes two to three minutes. “Unloaded” means you cycle or walk without any added resistance. Your technician gathers “active baseline” information. This is data on how your heart and lungs respond to the lowest possible level of exercise.
  4. Incremental exercise phase: This usually takes eight to 12 minutes. You cycle or walk steadily, without stopping, as your technician gradually adds resistance to the machine. It’ll feel harder and harder to continue. During this phase, your technician asks you to share how you’re feeling. It’s crucial to cycle or walk as long as you can.
  5. Recovery phase (cooldown): This lasts three to five minutes. You cycle or walk with no resistance, as you did at the start. Your technician checks your vital signs and measures your heart rate recovery. Once your heart rate and blood pressure return to normal, you can prepare to leave.

Rating of perceived exertion (RPE) scale

During the test, you share how you’re feeling by using a rating of perceived exertion (RPE) scale. Healthcare providers use several possible RPE scales. The most common one for CPET involves raising your fingers and signaling how hard it is to breathe, and how tired your legs feel, on a scale of 0 to 10. The higher the number, the more exhausted you feel.

All the equipment captures a wealth of data about what’s going on inside your body, but you’re the only one who can say how you feel. So, it’s important to ask your lab technician any questions you have about the scale before beginning.

How will I feel during the test?

To get the most accurate and helpful test results, you should exercise until you’re exhausted. It’s normal for your heart rate, blood pressure and breathing rate to go up. You’ll also feel sweaty, and your legs will feel more and more tired. Your mouth may feel dry from breathing through the mouthpiece.

This is a workout, and it’ll feel like a workout. But if you have unusual symptoms during the test, stop exercising and tell your technician immediately. These symptoms include:

  • Pain, discomfort or tightness in your chest, arm or jaw.
  • Extreme shortness of breath.
  • Dizziness or feeling like you’re going to pass out.

Such symptoms could signal a heart attack or other medical emergency. Lab technicians will watch for any worrisome changes on the EKG monitor, and they’ll stop the test immediately if needed.

How long does the test take?

Your appointment will take about 75 minutes. You’ll actually be exercising for up to 20 minutes, including your warmup and cooldown.


Results and Follow-Up

How do I get the results of my test?

Your healthcare provider will tell you when and how you can access your results. You’ll likely see your results in your electronic medical record, and you’ll also meet with your provider to discuss them.

This test records thousands of measurements into a format known as a nine-panel plot. This is a set of complex, technical graphs that show extensive detail about your heart and lung function. Your provider will interpret these results and explain them to you.

A note from Cleveland Clinic

Anticipating your metabolic exercise stress test might make you feel stressed out. And that’s normal. But don’t panic or worry too much about what’ll happen during the test. This test is a routine procedure that gives you and your provider extraordinary insight into the inner workings of your heart and lungs.

It might feel strange to have electrodes and various devices hooked up to your body as you’re trying to exercise. But know that each device is capturing vital information that’ll help your provider coordinate the care you need. Don’t hesitate to reach out to your provider before your test with questions about how to prepare or what you can expect when you arrive at the lab.

Medically Reviewed

Last reviewed on 09/28/2022.

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