Cardiopulmonary exercise testing (CPET) is a method used to assess the function of the cardiovascular and respiratory systems during exercise. It involves measuring various physiological parameters, such as heart rate, oxygen consumption, carbon dioxide production, and ventilation, while a person performs incremental exercise on a treadmill or stationary bike. CPET is often used in clinical settings to evaluate exercise capacity, identify cardiovascular and respiratory limitations, and guide exercise prescription for individuals with chronic diseases or athletes. It can also be used to diagnose certain medical conditions, such as heart failure, pulmonary hypertension, and exercise-induced asthma. Overall, CPET provides valuable information about an individual's fitness level and helps healthcare professionals tailor treatment and exercise programs to optimize health and performance.