The human sexual response cycle is a four-stage model of physiological responses during sexual stimulation. These phases, in order of their occurrence, are the excitement phase, plateau phase, orgasmic phase, and resolution phase. The term was coined by William H. Masters and Virginia E. Johnson in their 1966 book Human Sexual Response.
The excitement phase (also known as the arousal phase) is the first stage of the human sexual response cycle. It occurs as the result of any erotic physical or mental stimulation, such as kissing, petting, or viewing erotic images, that lead to sexual arousal. During the excitement stage, the body prepares for coitus, or sexual intercourse, in the plateau phase.
During the female sex flush, pinkish spots develop under the breasts, then spread to the breasts, torso, face, hands, soles of the feet, and possibly over the entire body. Vasocongestion is also responsible for the darkening of the clitoris and the walls of the vagina during sexual arousal. During the male sex flush, the coloration of the skin develops less consistently than in the female, but typically starts with the epigastrium (upper abdomen), spreads across the chest, then continues to the neck, face, forehead, back, and sometimes, shoulders and forearms.
The sex flush typically disappears soon after orgasm occurs, but this may take up to two hours or so, and sometimes, intense sweating will occur simultaneously. The flush usually diminishes in reverse of which it appeared.
An increase in muscle tone (myotonia) of certain muscle groups, occurring voluntarily and involuntarily, begins during this phase among both sexes. Also, the external anal sphincter may contract randomly upon contact (or later during orgasm without contact).
The plateau phase is the second phase of the sexual cycle, after the excitement phase. Further increases in circulation and heart rate occur in both sexes, sexual pleasure increases with increased stimulation, muscle tension increases further.
During this phase, the male urinary bladder closes (so as to prevent urine from mixing with semen) and muscles at the base of the penis begin a steady rhythmic contraction. Males may start to secrete seminal fluid and the testicles rise closer to the body.
At this stage females show a number of effects. The areola and labia further increase in size, the clitoris withdraws slightly and the Bartholin glands produce further lubrication. The tissues of the outer third of the vagina swell considerably, and the pubococcygeus muscle tightens, reducing the diameter of the opening of the vagina and creating what Masters and Johnson refer to as the orgasmic platform. For the women who never achieve orgasm, this is the peak of sexual excitement. Both men and women may also begin to vocalize involuntarily at this stage.
Prolonged time in the plateau phase without progression to the orgasmic phase may result in frustration if continued for too long (see Orgasm control).
Orgasm is the conclusion of the plateau phase of the sexual response cycle, and is experienced by both males and females. It is accompanied by quick cycles of muscle contraction in the lower pelvic muscles, which surround both the anus and the primary sexual organs. Women also experience uterine and vaginal contractions. Orgasms are often associated with other involuntary actions, including vocalizations and muscular spasms in other areas of the body, and a generally euphoric sensation.
In men, orgasm is usually associated with ejaculation. Each spurt is associated with a wave of sexual pleasure, especially in the penis and loins. The first and second convulsions are usually the most intense in sensation, and produce the greatest quantity of semen. Thereafter, each contraction is associated with a diminishing volume of semen and a milder wave of pleasure.
Orgasms in females may also play a significant role in fertilization. The muscular spasms are theorized to aid in the locomotion of spermatozoa up the vaginal walls into the uterus.
Men and women may not experience this refractory period and further stimulation may cause a return to the plateau stage. This allows the possibility of multiple orgasms in both sexes. However, some may find continued stimulation to be painful after the orgasmic phase.
In addition, refractory periods range from human to human, with some being immediate (no refractory) and some being as long as 12 to 24 hours.
Intercourse often ends when the man has ejaculated. Thus the woman might not have time to have an orgasm. In addition, many men suffer from premature ejaculation.
According to a Kinsey study, just under half of men reported a time to ejaculation from intromission of five minutes or less. About a fifth claimed that coitus lasted 10 minutes or longer. Others may have taken over one hour. Taking too long, however, can turn pleasure into pain.
How long should sex last? A collaborative poll of the readers of Marie Claire and Maxim magazines conducted in July 2004 showed the following:
The survey shows the largest group for women not setting a time limit and the largest group for men setting a time limit at female orgasm. Male orgasm is not mentioned. Comparing as long as possible and forever shows that 44% of women and 32% of men prefer an undefined time greater than 30 minutes.
In spite of the common belief that women need more time to get aroused, recent scientific research showed that there is no considerable difference for time men and women require to get fully aroused. Scientists from McGill University Health Centre in Montreal, Canada used the method of thermal imaging to record baseline temperature change in genital area to define the time necessary for sexual arousal. Researchers studied the time required for an individual to reach the peak of sexual arousal while watching sexually explicit movies or pictures and came to the conclusion that on average women and men took almost the same time for sexual arousal - around 10 minutes. The time needed for foreplay is very individualistic and varies from one time to the next depending on many circumstances.
A survey of Canadian and American sex therapists said that the average time for intromission was 7 minutes and that 1 to 2 minutes was too short, 3 to 7 minutes was adequate and 7 to 13 minutes desirable, while 10 to 30 minutes was too long.
This article is based on "Human sexual response cycle" from the free encyclopedia Wikipedia (http://en.wikipedia.org). It is licensed under the terms of the GNU Free Documentation Licencse. In the Wikipedia you can find a list of the authors by visiting the following address: http://en.wikipedia.org/w/index.php?title=Human+sexual+response+cycle&action=history