Does yawning in the heat of the moment mean you're bored — or what? And can sex improve your skin? Sexploration answers your queries. Got a question? E-mail us .

Q. During sex, I have an issue with yawning. As soon as we settle down, I start yawning big time. I explain it as an oxygen debt, nothing more, but it’s confusing to my lover. Why does my body want oxygen at a time like this?

A. Yes, yawning in your lover’s face could be a bit deflating, as if you’re saying “Can we move it along? I’m in the middle of the new Janet Evanovich.”

Good try with that whole “oxygen debt” thing, though. It sounds kind of scientific and a little like you are prepping for the sex equivalent of freestyle wrestling. Woo hoo! But you’re wrong. It’s not that your body wants oxygen at a time like that, your body wants oxygen … well, all the time and if you wanted more, you wouldn’t yawn, you’d just breath more deeply and rapidly.

No, yawning during sex has a much more interesting — and encouraging — explanation.

Sometimes, to do certain studies, scientists have to make horny mice. (Instead of wheel running and dissection, some lab mice luck out and spend their lives in the equivalent of Hugh Hefner’s smoking jacket.) And do you know how scientists can tell if the mice are in the mood? They check for “stretching and yawning behaviors.”

Yawning, argues Dr. Robert Provine, a neuroscientist, professor of psychology, and yawning expert (yes, yawning expert) at the University of Maryland, Baltimore County, is an evolutionary trait conserved across all vertebrate species. Fish do it, lions do it, we do it. It is so embedded in the primitive parts of our brains that fetuses do it in utero.

We do it for a variety of reasons, like boredom or as social instinct — the so-called contagious yawn. You may be yawning right now because you are reading about yawning. (Don’t worry, I won’t take it personally.) But as Provine, who has also authored a book called “Laughter: A Scientific Investigation,” has pointed out, paratroopers ready to jump out of airplanes and into battle are prone to yawning, as are dogs just before they attack and it’s safe to say they are not bored.

Yawning, in fact, is also a sign of arousal. Biochemically speaking, it may be caused by the release of dopamine in the brain which may trigger a cascade of other brain chemicals like oxytocin and nitric oxide, the stuff erections are made of, among them. For example, when scientists experimenting with Melanotan, or PT-141, ( a drug we’ve covered here before ) tried it on people, they found that in addition to creating erections, “nausea and yawning were frequently reported side effects.”

As Provine explained to me, a yawn “serves a number of functions but a common feature in all is that it is associated with a change of state, a shift, say, from sleep to wakefulness, wakefulness to sleep.” So when you shift from not aroused to aroused, you yawn. Yawning at the moment of impending sex, he said, “is not at all rare.”

Dutch scholar Wolter Seuntjens has an interesting Web site exploring the eroticism of the yawn, and Provine speculates that sexual climax and yawning may “share a neurobehavioral heritage.”

You’re not bored, or starved for oxygen. You’re just turned on.

Q. I am a very sexually active woman. I am 41 years old and I am full of energy. My question is, does having sex improve your skin? I have noticed a naturally bright glow after I have sex.

A. Next time you go to your gym and give yourself a good StairMaster workout, or walk vigorously in the park, or ride your bike to the store and back, look in the mirror. Actually, wait until after you’ve stopped sweating and feeling like you are going to pass out, then look in the mirror.

See that bright, glowing skin? When you exercised, your blood vessels dilated and you sent lots of blood closer to the surface of your skin to help cool your body. You also pumped a lot of oxygen into those red blood cells through all that heavy breathing. Now, can you think of any other activity that might make you perspire and breathe heavily?

Thought so. More blood and oxygen in skin is attractive to others. A recent study by researchers from the University of St. Andrews in Scotland found that men selected photos of women featuring a slightly rosier glow as being more attractive. Women liked a bit of rose in men, too, but not as much.

Many women, and some men, experience what is called a “sex flush” just before and during orgasm. NARS, the cosmetics maker, exploits this with blushers called “Orgasm” and “Super Orgasm.”

So we may like the glow because it reminds us of sex or because it signals health. In fact, you might have good health, and so have your rosy glow, and your health may be why you enjoy sex so much, not that sex is causing your glow.

Which is not to say that sex itself does not help your skin, necessarily. The skin is a wildly complex organ. Among other traits, it has lots of receptors for sex hormones like testosterone and estrogen. This helps explain why some women find acne relief by taking birth control pills.

But while researchers have documented a rosy blush when women are aroused, there’s never been a study that proves sex makes for good skin. Wouldn’t such a study be fun? You might even feel happier during it. You might smile a lot and feel good about yourself. You might glow.

Brian Alexander is the author of the book “America Unzipped: In Search of Sex and Satisfaction," now in paperback.