With regard to pain or being uncomfortable during anal sex, some research indicates that, for 24% to 61% of gay or bisexual men, painful receptive anal sex (known as anodyspareunia) is a frequent lifetime sexual difficulty. indicated that orgasm rates are similar among men across sexual orientations. A study sampling single people in the U.S. A study by the National Survey of Sexual Health and Behavior (NSSHB) indicated that men who self-report taking a receptive position during anal sex in their last encounter were at least as likely to have reached orgasm as men who adopted an insertive role. While the nerve endings in the anus can provide pleasurable feelings, an orgasm may be achieved through receptive anal penetration by indirect stimulation of the prostate. Pleasure, pain, or both may accompany anal sex. When MSM engage in anal sex without using a condom, this is referred to as bareback sex. Īmong men who have anal sex with other men, the insertive partner may be referred to as the top, the one being penetrated may be referred to as the bottom, and those who enjoy either role may be referred to as versatile. Many MSM, however, do not engage in anal sex, and may engage in oral sex, frottage or frot, or mutual masturbation instead. Historically, anal sex has been popularly associated with male homosexuality and MSM. The penetrating man on the right is the 'top' and the receptive man on the left is the 'bottom' in missionary position.