The most common type of erotic spanking is administered on the bare buttocks, but can also be combined with bondage, in order to heighten sexual arousal and feelings of helplessness. Diaper fetishism is totally independent from pedophilia as the wearer derives pleasure only from the diaper and/or use of it. Many cultures describe pain as an aphrodisiac. Those with diaper-related paraphilias differ widely in their focus of attention. The use of the word creampie to describe such scenes originated in U. Both sexes sometimes apply lubricating substances to intensify sensation. The most common male masturbation technique is simply to hold the penis with a loose fist and then to move the hand up and down the shaft. They may regard it as an enhancing element of their sex lives or as their primary form of sexual activity. In humans, females generally have more round and voluptuous buttocks, caused by estrogen that encourages the body to store fat in the buttocks, hips, and thighs. The act may be carried out face to face, or head to tail, with the woman recommended to be on top if she has smaller breasts. When used as an alternative to penile-vaginal penetration, the goal may be to preserve virginity or to prevent pregnancy. In Japanese, the term describes any type of perverse or bizarre sexual desire mature milfs or act; it does not represent a genre of work. Additionally, the buttocks give an indication of the shape and size of the pelvis, which impacts reproductive capability. Mammary intercourse is known as titty-fucking, titfuck, or a titjob in the United States, as well as tit wank or French fuck in the United Kingdom - the latter term dating back to the 1930s; while a more jocular equivalent is a trip down mammary lane. Buttocks are sometimes emphasized in pornography, where gay movies they are often referred to as booty. Crush pornography features objects being hentai movies crushed by an actress or actor, who generally plays an overtly dominant role. Clothed female, naked male pornography features naked men and clothed women; typically, the women humiliate and abuse the men or perform fellatio and/or handjobs on the men.