I had never heard of Traumatic Masturbatory Syndrome until today, but its apparently a medical theory that says that guys masturbating while laying face down are more prone to severe sexual dysfunction. [via Go Ask Alice]

Some TMS practitioners rub their penises against the mattress, pillow, or other bedding, while others thrust into their hand. Some rub against the floor.
Masturbating face-down puts excessive pressure on the penis, and especially on the base of the penis. These sensations are not easily replicated in conventional masturbation or in sexual intercourse. This can make TMS practitioners unable to have normal sexual relations.