Muscle worship (also called sthenolagnia) is a form of body worship in which one participant, the worshiper, touches the muscles of another participant, the dominant, in a sexually arousing manner. The practice of muscle worship can involve various wrestling holds and lifts, as well as the rubbing, massaging, kissing, or licking of a dominant's body. Although muscle worship participants may be of any gender or sexual orientation, the dominant (often a professional bodybuilder, fitness competitor, or wrestler), is almost always an individual with either a large body size or a high degree of visible muscle mass, while the worshiper is often, but not always, skinnier or smaller.
The Encyclopedia of Unusual Sex Practices lists sthenolagnia ("sexual arousal from displaying strength or muscles") and cratolagnia ("arousal from strength") as paraphilias associated with the practice of wrestling for erotic purpose, although there have been no studies concerning them. Forensic and Medico-Legal Aspects of Sexual Crimes and Unusual Sexual Practices, the 2008 comprehensive monograph of Anil Aggrawal, only defines the two terms, and does not provide any additional information.
As with many BDSM-related practices, the amount of force and pain involved depends on the desires of the participants. While some dominants might use their size and strength to pin a smaller worshiper, thereby forcing that worshiper to come in contact with the dominant's muscles, others might only display their muscles and allow a worshiper to touch them. People who participate in muscle worship generally find the practice sexually arousing, but some male bodybuilders offer muscle worship sessions only for monetary gain, as bodybuilding does not always guarantee a steady income. For well-known competitors, this can also draw in fans who want a chance to meet with and touch the muscles of bodybuilders whom they idolize.
Muscle worship is very prevalent among gay men, hence the large number of websites that display bodybuilders posing for admirers and offering private online posing shows. There are also sites devoted to women who enjoy worshiping male bodybuilders. Many other sites are oriented towards straight men who enjoy worshipping female bodybuilders and other fit, muscular women, either virtually or by arranging for in-person sessions.
- John Edward Campbell, Getting it on online: cyberspace, gay male sexuality, and embodied identity, Routledge, 2004, ISBN 1-56023-432-6, pp. 141-145
- Benoit Denizet-Lewis, America Anonymous: Eight Addicts in Search of a Life, Simon and Schuster, 2009, ISBN 0-7432-7782-1, pp. 94-96
- Hunks, hotties, and pretty boys, Cambridge Scholars, 2008, ISBN 1-4438-0018-X, pp. 159-164
- Shaun Assael, Steroid Nation, ESPN Books, 2007, ISBN 1-933060-37-9, book excerpt
- American Beauty, HBO Special Real Sports with Bryant Gumbel, #160 aired on July 14th, 2010 official synopsis, a text summary and critique, streaming video: part 1, part 2 (the muscle worship proper coverage starts at 3:30 in the 2nd part)
- Love, Brenda (1994). The Encyclopedia of Unusual Sex Practices. Barricade Books, Incorporated. p. 313. ISBN 1-56980-011-1.
- Google scholar search returns only  as of 3 Oct. 2010
- Aggrawal, Anil (2008). Forensic and Medico-Legal Aspects of Sexual Crimes and Unusual Sexual Practices. CRC Press. p. 372 and 380. ISBN 1-4200-4308-0.
- Muscle Worship, Hidden Lives series, Channel Five, 9 Apr. 2007, imdb entry, streaming video