Men are often criticized for sleeping their asses off after sex, but there may be good reasons for this.
first of all, the most obvious reason why men feel sleepy after sex is the sleep-inducing “rocking back and forth” part of sex. this is usually done at night and in bed, and it is very tiring work. it is often much more tiring for men than for women. so it is natural for men to feel physically tired and sleepy when sex is over.
Secondly, research with positron emission tomography shows that in order for a person to reach orgasm, they need to let go of all fear and anxiety, which may have a relaxing and sleep-inducing effect.
third, there is the biochemistry of orgasm itself. research shows that when men ejaculate, their brains release a cocktail of chemicals. these chemicals include norepinephrine, serotonin, oxytocin, vasopressin, nitric oxide and prolactin. prolactin is associated with sexual satisfaction. it is also the hormone that determines the regeneration time needed for men to prepare for sex again. as all men know, they have to wait a certain amount of time before they can “do it again”. this is the regeneration time. research shows that men who are low in prolactin are able to have sex more often.
prolactin levels are naturally higher during sleep. in animal experiments, animals injected with prolactin appear to fall asleep instantly. this suggests a strong relationship between prolactin and sleep. therefore, the hormone’s secretion during orgasm may be the reason why men feel sleepy.
