Imaging studies in women have shown that their brains are undergoing a fascinating set of changes post orgasm. These include increased activity of the areas associated with relaxation, touch, reward, memory, and pain sensation.
Apparently, orgasm is a pretty reliable pain desensitizer for women. This effect may last for hours after. Along with this comes decreased anxiety and less activity in the parts of the brain associated with fear and what researchers describe as a "trance-like state."
While I don't have a double-blind study to quote here, I'd love to see a study that looked at whether these brain changes result in increased weight lifting PRs for females. Less fear, less anxiety, greater trace-like focus, and greater pain tolerance? Sounds like the optimal mental state. Could orgasm be a performance enhancer for women? It seems likely.
Sorry guys, there are no similar studies of the male brain. It look like the fear, anxiety, and pain reductions may be female specific.