While anal sex is commonly associated with male homosexuality, research shows that not all gay males engage in anal sex and that it is not uncommon in heterosexual relationships. Two women tapegagged and cuffed to iron bars Bondage and Discipline are two aspects of BDSM that do not seem to relate to each other because of the type of activities involved, but they have conceptual similarities, and that is why they appear jointly. A bisexual threesome may involve a man having sex with a man and a woman, the woman having sex with a man and a woman, or all three having sex with each other. The volume of semen that is ejaculated depends on several factors, including the male health, age, degree of sexual excitement, and the time since his last ejaculation. Irrespective of the legal or social view of pornography, it has been used in a number of contexts. John Stagliano is considered to have started the gonzo pornography genre with his Buttman series of films. Boots are seen as the perhaps most fetishistic of all footwear and boots may be the most popular fetish clothing attire. Yaoi is anime or manga that features gay males . Although there may be no connection between coprophilia and sadomasochism , the limited data on the former comes from studies of the latter. As a form of non-penetrative sex, it can be done for its own enjoyment or as foreplay. A survey by the New York City Department of Health and Mental Hygiene found that heterosexual women are more likely to bareback when engaging in anal sex than homosexual and bisexual men. Participants who exert sexual control over their partners are known as dominants or tops while participants who take the passive, receiving, or obedient role are known as submissives or bottoms. The term sadomasochism is derived from the words sadism and masochism . Mutual masturbation, porno gay mutual manual stimulation of the genitals between partners, can be a substitute for sexual penetration. However, various groups within society considered such depictions immoral, labelling them pornographic, and attempting to have them suppressed under obscenity laws, with varying degrees of success.