A researcher at the University of Paisley has determined that having regular penetrative sex (and only penetrative sex) makes people into better, more relaxed public speakers:
For a fortnight, 24 women and 22 men kept diaries of how often they engaged in various forms of sex.
Then they underwent a stress test involving public speaking and performing mental arithmetic out loud.
Volunteers who had had penetrative intercourse were found to be the least stressed, and their blood pressure returned to normal faster than those who had engaged in other forms of sexual activity such as masturbation.
Those who abstained from any form of sexual activity at all had the highest blood pressure response to stress.
(Thanks, Olivia!)
Update: Ken sez, "Just because people who have sex
are less stressed doesn't mean that the sex causes them be that way.
At least as plausible is that they have more sex _because_ they are
less stressed and recover from stress more quickly– stress and
staying steamed being a turn-off, in general, not to mention
physiological effects of stress on performance, for men."
