Holding your breath does not test lung function. Breath-holding refers to the conscious not-breathing, in which a deep or shallow inhalation is followed by a tightly closed vocal fold without breathing. Holding the breath reflexively induces an increase in muscle tone, which can create the most effective contraction support conditions for the relevant motor link. Therefore, usually in the completion of the maximum static exertion of the movement, need to hold your breath to cooperate, such as large loads of weight bearing, weight lifting exercises, wrestling, tug of war, “arm wrestling” and so on. The length of breath-holding time is only used to measure the body’s tolerance to hypoxia, not to test lung function. For patients with bronchial asthma, chronic obstructive pulmonary disease (COPD), pulmonary heart disease (PHD) and other diseases, lung function status can be assessed through specialized pulmonary function tests. Lung function includes ventilation function and gas exchange function. Ventilation function refers to the exchange of gases between the lungs and the outside world, and gas exchange function refers to the exchange of arterial and venous blood of the body within the lungs. Through pulmonary function tests, you can clearly know what level of lung function you have reached, which is a guide for treatment and daily exercise.