It is a normal phenomenon that the heart rate is sometimes fast and sometimes slow, which is compatible with the daily physiological activities of human beings. For example, when a person is resting quietly, all organs of the body are in a state of low metabolism, in which the excitability of the vagus nerve increases and the excitability of the sympathetic nerve decreases, the effect on the heart is that the contraction of the heart muscle is weakened, the conduction of the heart slows down and the heart rate becomes slower, which helps rest of the patient as well as a good recovery of physical performance. During exercise or emotional excitement, the metabolism of all organs of the body is relatively strong, sympathetic excitability increases, vagal excitability decreases, the contraction of the heart is strengthened, heart conduction is accelerated, and the heart rate increases, which helps to engage in various activities.