Although each individual differs in how he or she enjoys and reacts to sexual stimuli, the American researchers W.H. Masters and V.E. Johnson have identified four distinct physical stages that everyone, male and female, passes through if they achieve orgasm. They called these stages excitement, plateau, orgasm and resolution.
Excitement stage
The excitement stage can last from a few minutes to several hours and may begin through physical stimulation such as kissing or fondling. Equally, you can become excited by thinking about somebody you love or desire, or by being near that person. The most noticeable part of this phase is the effect it has on the erectile tissue, primarily the penis in the man and nipples in the woman. Within 10 to 30 seconds of becoming sexually excited, most men will have an erection as blood flows into the spongy tissue (the corpus cavernosa) of the shaft of the penis. At the same time, the scrotal sac tightens and pulls the testes up towards the body. Some men also experience nipple erection.
The female body exhibits a wider range of reactions during the excitement stage. Not only do the nipples themselves become engorged and erect but the areola, the dark area around the nipple, also enlarges. Veins on the breast fill and stand out. In most women, the clitoris swells and lengthens and the labia minora and majora (the inner and outer vulval lips) also react, with the outer lips increasing in size by two to three times and the inner lips flushing dark red. Changes also occur inside the vagina, which becomes purple in patches and secretes a clear liquid to make intercourse comfortable and to give the sperm easy passage on their way to the Fallopian tubes. The vagina itself changes shape and size: the innermost two-thirds expands and the uterus, or womb, is pulled up into the pelvic cavity, giving more room for the thrusting penis.
Signs of sexual excitement are also visible on the face of both the man and the woman. Lips and ear lobes mimic other erectile tissue by flushing and swelling, and the cheeks may flush as well. Eyes appear to sparkle and pupils dilate. There are also marked increases in pulse, blood pressure and rate of breathing. Pulse rates may climb from a normal 70 to 80 beats per minute to more than 100 as the sexual response becomes more intense.
Paradoxically, during sexual excitement, although it may seem that your senses are heightened, you can in fact become surprisingly insensitive to what is happening around you. You can be scratched or hit or even have people walk into the room and move near you, without noticing a thing.
Plateau phase
At some point during the excitement phase, the couple are likely to start intercourse, in which the penis enters the vagina. Excitement can continue for some time, however, before the second, or plateau, phase is reached. Reaching the plateau phase is a clear signal that orgasm is near and will probably occur within a few minutes. There are unmistakable signs that the plateau phase has begun, and if you want to prolong your love-making, you should learn to recognize these, and stop for a short time.
As the plateau phase starts, a mottled flush may spread over the stomach to the chest, neck, face and sometimes even the arms, thighs and buttocks of both partners. This rash is particularly noticeable on the woman's breasts. These will swell, sometimes by as much as one-fourth their normal size, and the areolae may enlarge so much that the nipples seem to disappear. The man's testes enlarge as well, his penis increases further in size and the glans deepens in colour to purple. In the woman, the clitoris actually retracts at this stage, withdrawing into the swollen wall of flesh (the prepuce) that surrounds it. If orgasm is delayed, the shaft of the clitoris may relax and retract several times. The outer lips of the vagina can become so enlarged and thick that they appear to hang like folds of cloth, and the inner lips flush a deep red. The vagina continues to flow with secretions and its walls now turn a deep purple. The innermost two-thirds expands still further, while the outer third contracts around the man's penis. This allows the clitoris to get maximum stimulation from the thrusts of the penis stretching the labia and clitoral prepuce. As orgasm approaches, the womb starts to have contractions similar to those during labour.
Orgasm phase
As the third phase, orgasm, becomes imminent, pulse rates may leap to as much as 180 beats a minute – as high as that of a sprint athlete or someone doing heavy physical work. Blood pressure is dramatically increased, and, in very rare cases, men and women do actually ‘black out', momentarily losing consciousness during orgasm.
In the man, orgasm is characterised by ejaculation. The vas deferens, seminal vesicles, prostate and urethra all contract spasmodically to force seminal fluid up the penis and out into the woman's vagina. In the woman, the womb contracts strongly, as does the outer third of the vagina and even the inner labia. Both the man and the woman momentarily lose control of muscles, both those normally under conscious control and those under reflex or involuntary control. In most men, and some women, the anal sphincter muscle contracts and hands may flex, toes curl, and stomach, buttock and thigh muscles ‘jump'. The face and neck muscles may also tense; during orgasm, some people look as if they are in intense pain and their eyes take on a fixed and glaring expression. Women can have multiple orgasms but men usually have only one Immediately after orgasm men go through a refractory phase during which they cannot achieve a further erection, no matter what the stimulation. Some young men at their most sexually potent, at about the age of 18 years, may find that they can indeed have another orgasm once the refractory phase is over, perhaps within 30 minutes. Older men, however, usually need a longer period, as much as 12 hours being quite normal.
Resolution phase
The final phase of coitus is resolution. This can last from 10 to 15 minutes. If orgasm has not been reached, the changes that occur during resolution can take up to 24 hours. Not surprisingly, if this is the case you can be left not only emotionally tense, but physically drained and sore. During resolution, the flush that covered both man and woman fades. The man's penis shrinks to its normal, flaccid size, and his testes decrease and drop. The woman's breasts also return to normal size and the nipples soften and flatten. Her clitoris and labia become less swollen and the vagina retracts to its original position.
