Cardiopulmonary exercise testing What is cardiopulmonary exercise testing and what can it show? Cardiopulmonary exercise testing (CPET) is a type of exercise test. It can tell the healthcare team how much exercise you can do. How is cardiopulmonary exercise testing done? CPET involves breathing into a mouthpiece while riding an exercise bike or walking on a treadmill. You will also normally be connected to an electrocardiogram (ECG) machine to monitor your heart.