Every Friday on the blog, I answer people's questions about sex, love, and relationships. Today’s question comes from a reader who wanted to know the following:

“What’s your favorite sex fact?”

That’s a tough question! I mean, asking a sex researcher to pick their favorite sex fact is kind of like asking a parent to choose their favorite child. Well, maybe not quite like that—but it is really hard because I have come across so many interesting sex facts over the years. Below, I give you eight of my personal favorites because I couldn’t narrow the list down any more than this. Enjoy!

1. The most orgasms ever documented in an hour for a woman is a mind-boggling 134! For men, the record is *just* 16 [1].

2. Nocturnal orgasms aren’t just for men—women can have them too! In fact, in Alfred Kinsey’s groundbreaking research on female sexuality, he found that 37% of women reported having at least one nocturnal orgasm by age 45. You can read more about research on female nocturnal orgasms here.

3. “Morning wood” isn’t just for men either—women often wake up with the clitoral equivalent of morning wood [2]! People naturally experience 4-5 penile or clitoral erections per night as they cycle in and out of REM sleep.

4. A recent study demonstrated that, on average, sex burns 101 calories for men and 69 (hee hee!) calories for women. Learn more about this research and how sex stacks up to other forms of exercise here.

5. Some women experience orgasms from nipple stimulation, and science tells us why: fMRI research has revealed that stimulation of the nipple activates the same region of the brain (the genital sensory cortex) as stimulation of the vagina, cervix, and clitoris. You can learn more about the “nipplegasm” here.

6. Men demonstrate enhanced functioning of their immune systems right after orgasm [3]. Could this ultimately improve their health? It would seem so. Research has also found that men who orgasm more frequently tend to live longer [4]!

7. The vibrator was originally invented as a treatment for women suffering from “hysteria,” a once common but bogus medical condition that doctors thought was caused by inadequate or insufficient sex. When vibrators first entered the market, demand was so strong that they became just the fifth electric device approved for home use after the sewing machine, fan, teakettle, and toaster! Read more about the “hysterical” history of the vibrator here.

8. The distance between a woman’s clitoris and her vaginal opening predicts her likelihood of having an orgasm during intercourse [5]. Here’s a handy rule of thumb: when the distance is less than the width of her thumb, a woman is more likely to reach orgasm without the need for added clitoral stimulation.

Do you have a favorite sex fact (or eight)? Include your personal favorites in the comments section below. Bonus points if you include the source of the fact!

For previous editions of Sex Question Friday, click here. To send in a question for a future edition, click here.

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[1] Campbell, B., Hartman, W.E., Fithian, M.A., & Campbell, I. (1975). Polygraphic survey of the human sexual response. Physiologist, 18, 154.

[2] Siegel, J. M. (2005). REM sleep. Principles and practice of sleep medicine, 4, 120-135.

[3] Haake, P., Krueger, T. H., Goebel, M. U., Heberling, K. M., Hartmann, U., & Schedlowski, M. (2004). Effects of sexual arousal on lymphocyte subset circulation and cytokine production in man. Neuroimmunomodulation, 11, 293-298.

[4] Davey Smith, G., Frankel, S., & Yarnell, J. (1997). Sex and death: Are they related? Findings from the Caerphilly Cohort Study. British Medical Journal, 315, 1641-1644.

[5] Wallen, K., & Lloyd, E. A. (2011). Female sexual arousal: Genital anatomy and orgasm in intercourse. Hormones and Behavior, 59, 780-792.

Image Source: 123RF.com

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