December 15, 2009 / Fun / 5 comments
As a man nears orgasm during stimulation of the penis, he feels an intense and highly pleasurable pulsating sensation of neuromuscular euphoria. These pulses begin with a throb of the anal sphincter and travel to the tip of the penis. They eventually increase in speed and intensity as the orgasm approaches, until a final “plateau” of pleasure sustained for several seconds, the orgasm.
During orgasm, semen is usually ejaculated and may continue to be ejaculated for a few seconds after the euphoric sensation gradually tapers off. It is believed that the exact feeling of “orgasm” varies from one man to another, but most men agree that it is highly pleasurable.
A typical woman’s orgasm lasts much longer than that of a man. It is preceded by erection of the clitoris and moistening of the opening of the vagina. Some women exhibit a sex flush, a reddening of the skin over much of the body due to increased blood flow to the skin. As a woman nears orgasm, the clitoral glans moves inward under the clitoral hood, and the labia minora (inner lips) become darker. As orgasm becomes imminent, the outer third of the vagina tightens and narrows, while overall the vagina lengthens and dilates and also becomes congested from engorged soft tissue. Elsewhere in the body, the breasts swell because myofibroblasts of the nipple-aerolar complex contract, causing erection of the nipples and contraction of the aerolar diameter, reaching their maximum at the start of orgasm. The uterus then experiences a series of between 3 and 15 muscular contractions. A woman experiences full orgasm when her uterus, vagina, anus, and pelvic muscles undergo a series of rhythmic contractions. Most women find these contractions very pleasurable. By the end of orgasm, breast size has returned to normal, but nipples take longer than the rest of the breast.
Recently, researchers from the University Medical Center of Groningen, the Netherlands, correlated the sensation of orgasm with muscular contractions occurring at a frequency of 8–13 Hz centered in the pelvis and measured in the anus. They argue that the presence of this particular frequency of contractions can distinguish between voluntary contraction of these muscles and spontaneous involuntary contractions, and appears to more accurately correlate with orgasm as opposed to other metrics like heart rate that only measure excitation. They claim to have identified “the first objective and quantitative measure that has a strong correspondence with the subjective experience that orgasm ultimately is”. They note that the measure of contractions that occur at a frequency of 8–13 Hz is specific to orgasm. They found that using this metric they could distinguish from rest, voluntary muscular contractions, and even unsuccessful orgasm attempts.