All kinds of stimuli that can cause pain, in its stimulus intensity is very weak, does not feel pain; when the stimulus reaches a certain intensity to feel pain. The so-called “pain threshold” refers to the minimum amount of stimulus to cause pain. For example, we can fill a bottle that can hold 500ml of water, when filling 499ml of water, the water is still not overflowing, if you continue to add water will be overflowing. Physiologically, a weak stimulus to the pain threshold does not produce pain, but when the stimulus is increased to a certain extent, if the intensity is increased, pain will be produced, just like water spilling out of the bottle. Of course, the problem of the pain threshold is much more complex than bottles of water. The pain threshold varies from person to person and is influenced by a variety of factors, such as age, gender, personality, psychological state, and the nature of the pain-causing stimulus. Clinically, some pain is caused by injurious stimuli, and some pain has an unclear stimulus. When a person is weak, the bioelectrical energy decreases, and if the bioelectrical energy of an organ is abnormal, it will lead to a decrease in the pain threshold of the relevant pathologic response area. The “pain threshold” is an undefined value. Healthy people have a high pain threshold and a high pain tolerance, while sick people have a lowered pain threshold and a weak pain tolerance and become more sensitive. A lowered pain threshold increases sensitivity to pain, and normal stimuli, such as changes in the body’s physiological range, can be painful. Over time, this can cause emotional changes and dysfunctions in the body, leading to vascular disease. Persistent muscle contraction can lead to vasogenic headaches and myotonic headaches, causing pain to the patient. Elevated pain threshold for stimuli beyond the pain threshold, but also can not feel the pain or delayed response, the disease can not be early detection, early diagnosis, loss of early treatment opportunities. In short, the elevation or lowering of the pain threshold is detrimental to the human body. The most commonly used pain threshold has two kinds: one is the pain perception threshold (customary as the pain threshold), that is, the beginning of the stimulus to know the intensity of the pain; one is called the pain tolerance threshold, that is, the maximum intensity of the pain can be tolerated. There are individual differences in pain thresholds, and there are also differences in different parts of the body. Pain has the role of protecting the body to avoid injury, that is, nociception can be used as a warning for the body injury, causing the body to occur a series of defensive protective reactions. However, the generation of nociceptive impulses requires that the stimulus intensity of pathogenic factors reaches a certain level before they can be generated, which is known as the problem of the pain threshold The pain threshold is also divided into the pain perception threshold and the pain response threshold. The pain threshold is the smallest amount of stimulation when the subject reports pain in words, and the maximum amount of injurious stimulation that the subject can tolerate is called the pain threshold. The pain response threshold is the minimum amount of injurious stimulation required to elicit somatic reflexes (e.g., reflexes, yelling, etc.) and endogenous reflexes (blood pressure, pulse, pupil, respiration, etc.). The endobirth reflex is an objective indicator that is not subjective.