What is the Cardiopulmonary Exercise Test? (CPET)

It is a test by which a person exercises to the point of exhaustion, where he/she can’t continue.  During this process, clinical data is obtained that will determine the limiting factors and endurance level.

What data is obtained and how is it useful to an individual?
These are some of the different measures that are obtained:

• The maximum oxygen consumption at peak exercise (VO2).
• The anaerobic threshold (the point at which the exercising muscles stop receiving oxygen, and lactic acid is accumulated).
• The maximal heart rate achieved.
• The maximal breathing rate.
• The efficiency of the heart and the lungs to mobilize during exercise.

Why is this useful?
Although many trainers and physicians predict the maximal heart rate based on age and sex, the fact is that every individual is different and has a different level of fitness. The CPET allows you to see how you measure compared to others of the same sex, age and size. Additionally, by identifying your anaerobic threshold you can target the important zone for training.

Is it difficult to do this test if are not in good shape?
No.  The test is performed on a bicycle ergometer.  There is no special skills needed and it is safe without the risk of falling or loosing your balance.

What is the anaerobic threshold and why is it important to determine it in a person?
Energy is needed for all bodily functions.  During exercise, the need for energy increases dramatically, especially in the primary muscles that are used.  Energy is provided by a substrate called ATP (Adenosine tri Phosphate).  Since this substance is so heavy, it cannot be stored to a great extent.  It must be constantly made and reused.

There are two ways in which ATP is made:

1. The aerobic pathway.  With this pathway, ATP requires oxygen that is delivered through the blood and exercise can be continued for a long time.
2. The anaerobic pathway.  With this pathway, exercise can only be continued for a limited period of time because oxygen no longer reaches the exercising muscle. As lactic acid accumulates, muscle fatigue will occur. 

The point where there is a shift from the aerobic to anaerobic pathway is the “anaerobic threshold.”  This threshold is important because once you know where your point lies you will know your “zone,” the point where exercise is most effective for you.

Is it possible or safe to exercise beyond the anaerobic threshold?
Yes, depending on your degree of fitness.  Muscles involved in exercise are capable of buffering lactic acid so that exercise can be carried out for longer periods of time. The length of time depends on training.  It is another reason to use the information obtained in the CPET before starting a fitness program.

What are some other measurements obtained in the CPET?