Rounding out Sci's first week of the Great Oxytocin Posting of 2009 (oh yes, there will be two weeks of this, hang tight), we've gotta do something weird. And luckily for everyone, oxytocin does lend itself to the strange types of studies. Like multi-orgasmic studies. Complete with measurements of anal contraction. You know you wanna volunteer for this one.
And luckily for all of you, Sci is the one doing the reading and the retelling of this study. Because reading the methods for this one might cause you to do this:
(Sci reading the methods)
Carmichael et al. "Relationships among cardiovascular, muscular, and oxytocin responses during human sexual activity". Archives of Sexual Behavior, 1994.
Also, we're stuck with another group of people who PUT ALL THEIR DATA IN TABLES!!! AUGH!!! Not only that, all of the tables in the pdf were in landscape, as opposed to portrait, which means Sci spent the entire time reading the paper like this:
Sci will fix for you. She graphs because she loves.
So anyway, as you may know from my previous post on the topic, oxytocin levels change during sexual arousal in women. They ALSO change during sexual arousal in men. In this study, the authors wanted to see whether oxytocin levels correlated specifically with orgasm, and what aspects of orgasm they correlated with.
So take 23 people, 13 women, 10 men. Make sure none of them are uncomfortable about the prospect of masturbating (apparently they have a questionnaire specifically for this, and I hope it also addresses the prospect of masturbating for a bunch of scientists who are going to be taking recordings of all of your physiological parameters). Put them in a sound-attenuated room with a TV (for those who requested porn) and a nice chair. Then, add a blood pressure cuff, a butterfly needle indwelling catheter for continuous blood level monitoring, and anal probes for monitoring of smooth muscle contraction. All these things are on really long leads that go into the next room, so the subjects can get some privacy.
Now, GO! What, you mean that's not comfortable?!
Luckily, they gave them two test sessions, one to get used to the room and surroundings, and another one to get used to the idea of blood sampling and anal probing during self-stimulation. So hopefully the discomfort became less of a factor. Finally, measures were taken twice for each subject, starting 6 minutes prior to self-stimulation, and continuous recording until 5 minutes AFTER.
And he's what they got:
(It shows what frame of mind Sci was in that she read the circled bit as "penis deflection")
You can see there a graphed representation of anal muscle contractions (a physical sign of orgasm), the volume of the anus at the time (another measure of anal contractions), and systolic blood pressure over the buildup to orgasm and the 5 minutes after. You can see that the blood pressure and anal contractions all peaked very nicely right at orgasm and fell off right after. The blood pressure showed the smallest change, and the APG (the anal volume measure) showed the largest change. The authors found no difference between the time the subjects SAID they were orgasming and the duration of the peak bodily effects, showing that (1) the subjects weren't lying, and (2) that the physical aspects go right along with the subjective experience.
And now we get into the stuff Sci had to look sideways to graph.
You can see above the mean duration of orgasm (how long it lasted) in seconds for men (in blue), for women who only had one orgasm (light pink), and for women who had two orgasms (the dark pinks). You can see that duration of orgasm didn't really differ between any of the groups, but hey, at least the multi-orgasmic women got to enjoy it twice. They did have ONE multi-orgasmic man, who had FOUR orgasms prior to actual ejaculation, but he was in a class all his own and I'm not going to bother graphing him if he doesn't come with a standard error and an n higher than one (though I will note that his longest orgasm was along the lines of 47 sec!).
They found that oxytocin levels in men and women peaked with orgasm, and that the oxytocin levels correlated with the "strength" of the orgasm, both in physical measures and in the patient's self-reports.
This is the second major graph, showing the strength of anal muscle contraction during orgasm for men, mono-orgasmic women, and multi-orgasmic women. You can see that the men appear to have the strongest anal muscle contraction by a good bit, while the women peak at about the same whether they have single or double orgasms.
But what's really cool about this study? What it actually LOOKED LIKE (no, not that, sicko)
Here you can see the simultaneous recordings for two different types of orgasm (apparently they were able to separate the orgasms easily into two different types). It shows very nicely how the muscle contractions and volume (the APG and EMG) go right along with the subjective measures of orgasm (the tick marks in 1 sec intervals. I really hope they didn't make the subjects fill out a sheet during or that's going to be one heck of a confound, maybe they just said "oh, right then!"?). You can also see that there's a little burst of muscle activity right before orgasm, and while the muscle contractions are pretty rhythmic, there are some pauses as well. You can also see that the EMG and APG measures correlated with each other in little bursts.
In measures of the two different types of orgasm, it appears that the second type (classified as type B) was generally longer (26.9 sec vs 16.3 sec), but had the same number of muscle contractions, so I guess you could call it "slower" as well.
Interestingly, in subjective measures afterward, the subjects all reported brief or long orgasms to be equally satisfying, despite the differences in the physical measures. So there were some subjective differences involved. But overall, the subjective measures of WHEN the orgasm occurred, the physical responses, and the hormonal responses (the peaks in oxytocin) all correlated very well.
The authors concluded several things:
1) Based on previous studies as well as the current one, blood pressure goes along with oxytocin levels, and some studies have shown that injection oxytocin increases blood pressure. So oxytocin could be having direct effects on blood pressure.
2) That oxytocin helps to stimulate the muscle contractions that occur with orgasm. Oxytocin is known to stimulate muscle contraction (like in the alveoli during lactation and in the uterus during birth), and so this isn't a particularly big stretch. Not only that, knowing that oxytocin can help stimulate the muscle contractions that occur with orgasm could help those who have problems with it, perhaps using supplemental oxytocin as the next Viagra (I really hope I didn't get people ideas with that one, I'm going to assume someone's thought of it already).
The take home message? For your next orgasm, thank oxytocin. It's about time it got credit for something fun.
Carmichael, M., Warburton, V., Dixen, J., & Davidson, J. (1994). Relationships among cardiovascular, muscular, and oxytocin responses during human sexual activity Archives of Sexual Behavior, 23 (1), 59-79 DOI: 10.1007/BF01541618