In 1966, Masters and Johnson concluded that the human sexual response cycle is a systemic cycle of arousal, orgasm, and return to a calm state, mainly in the sexual organs. In order to better understand the changes of anatomical structure and physiological response during sexual activity, the sexual response cycle is divided into four successive periods, i.e., excitement, plateau, climax and remission. The entire duration of the sexual response cycle varies from person to person, with the excitement period ranging from a few minutes to a few hours, the plateau period ranging from 0.3 to 3 minutes, the climax period ranging from 10 to 15 seconds, and the receding period ranging from 10 to 15 minutes. Generally speaking, about 3 / 5 men from the penis into the vagina about 2 minutes that ejaculation, 2 / 5 men can last 6 to 30 minutes, there are very few can be more than 1 hour. 1, the period of excitement Sexual excitement is caused by the physical or mental aspects of sexual stimulation. When a variety of stimuli caused by human sexual desire, and then triggered a series of conditional or unconditional reflexes, and entered the excitement period. After entering the arousal period, the white membrane around the spongy body is tensed due to the filling of the spongy body of the penis with blood, the penis becomes engorged and erect, the scrotal skin is filled with blood and thickened, the surface becomes smooth and stretchy, the contraction of the smooth muscle of the inner membrane makes the inner and outer diameter of the scrotum shrink, and the scrotum becomes hard and fixed. However, since the time of scrotal immobility or fixation is usually 5-10 minutes, the tight scrotum can be partially or completely relaxed if its sexual tension cannot reach the level of the plateau period. Therefore, in the case of conscious prolongation of the arousal period, the phenomenon of scrotal tightness and relaxation may occur for a long time, so that the levator muscle produces involuntary contractions and the testes can be specifically lifted in the direction of the perineum in a mobile manner. During the period of sexual excitement, it can be subject to any inappropriate stimulation, and the sexual excitement is weakened or disappeared, so that the erection of the penis becomes soft, such as the sudden appearance of panic in the environment, strong light, unfocused thoughts, mental laxity, pain, etc. 2, platform period In the platform period sexual tension is above the baseline level of sexual excitement, sexual excitement has reached a fairly high degree, but below the threshold level of orgasm. During this period, the penis is erect and firm, the glans becomes purplish red due to venous stasis or purplish red spots, overflow is common on the urethra, and the urethral bulbous glands are severely congested and secreted, especially when the platform period is consciously prolonged, the overflow is more. The overflow is often seen with motile sperm, which can lead to conception and is a detrimental aspect of in vitro ejaculation contraception. The urethra widens further in preparation for the massive outflow of semen, and the rapid expansion of the urethral bulb is often an important sign that the climacteric phase is approaching. The pumping action of the penis in the vagina during the platform stage can develop rapidly from a conscious and controlled random pumping to an uncontrollable mechanical violent lifting and thrusting impact, resulting in a rapid accumulation of sexual energy and a rapid growth of sexual tension in preparation for a smooth climax. In addition to the obvious thickening and tensing of the scrotal perineum, the phenomenon of hardening and fixation is more prominent, the testes are more engorged and their volume may increase by 1/2 to 1, and the elevation of the testes is also more obvious, and a rotation of 30 to 35 degrees may occur so that the posterior wall of the testes can finally adhere to the perineum. This process of elevation, rotation and fixation is necessary to obtain the most effective ejaculation. This lifting, rotation and fixation is not only an important indication that the climax phase will be entered, but also an important sign of the strength of ejaculation. 3, the climax period Sexual excitement and sexual continuity to a certain degree, after the sexual stimulation fully accumulated, will enter the climax period, only a few seconds, expressed as a high degree of penile erection, rhythmic contraction and ejaculation, changes in the scrotum and testicles similar to the platform period. Once ejaculation occurs, the testicles will soon begin to rotate again, and the scrotum gradually relaxes and gradually declines. 4, the receding period sexual excitement gradually fades, the penis from the erection of the receding to the swelling of the receding, until the complete return to the original state of weakness. In the ejaculation can still maintain close physical contact with the sexual partner, it can make this period longer. The non-response period is a special phase in men after ejaculation, characterized by the absence of sexual excitement to any sexual stimulation and the possibility of pain or discomfort to various direct stimulation of the penis. This is an instinctive human response. The period of inactivity lasts from a few minutes to a few hours, for most men, the period of inactivity is prolonged with age, newlywed husbands can have sex 2 to 5 times a night, while older people have more than enough heart, the period of inactivity up to a few hours or even a few days long.