Oxytocin is a lessor known hormone produced in several areas of the body including the testes, pancreas, pineal gland, thymus, adrenal glands, and ovaries. So it would seem apparent that this is an important hormone. You don't know the half of it yet.
In women, the level of Oxytocin dictates orgasm level and number. In fact the higher the Oxytocin level, the greater the number of orgasms. This hormone is also responsible for some smooth muscle contractions in blood vessels and organs. This is why women's uterus spasm and contract during orgasms. Some individuals are not aware of this tell-tale sign of a woman's lower abs pulsating (meaning they are achieving an orgasm). Oxytocin levels can also affect sexual sensitivity positively.
In men, Oxytocin causes smooth muscle in the pelvic area and prostate to contract which aids in ejaculation. In fact, there would be no post- sexual debate over who sleeps on the wet spot without Oxytocin.
So why is this fun hormone listed in a book about chemical muscle enhancement? Well, beside the fact that it is fun to write about it, Oxytocin has had reported beneficial bodybuilding effects.
Oxytocin triggers production of GH, IGF-1, PGE-1, PGF-2, and testosterone. Obviously those who claim sex before athletic competition is a bad thing are not only frustrated, but wrong as well. Oxytocin also induces vascular contractions which translates into significant vascularity if an athlete is lean enough. Unfortunately, the effects only last 40-60 minutes. But long enough for pre-judging.
There are only two methods of inducing elevated Oxytocin levels. First would be a trip to the closet with ones lover just before stepping on stage. (Yes, it is actually done) The second, is an exogenous source. Oxytocin is utilized to induce labor in farm animals, and is available in a powder form at many feed stores. Since the hormone is orally active, the rest should seem obvious. (But is not suggested!)
Hopefully exogenous Oxytocin use is wisely not your thing, remember that a good sex romp burns an average of 250 calories and aids in anabolic hormone production. Who says aerobics can't be mutually beneficial?
WARNING: The misuse use of oxytocin can be dangerous resulting in severe cramping and projectile defecation. Only a qualified trained medical person should administer oxytocin.
L. Rea (2002) - Chemical Muscle Enhancement Bodybuilders Desk Reference