MRI of sex - vaginal size + positions

Discussion in 'Sex With a Large Penis' started by ShannonH, Sep 16, 2011.

  1. ShannonH

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    The inside of a vagina during sex is sort of mysterious to everyone -- we generally know what feels good, but how things actually fit together down to the angles, cervical position, and vaginal tenting is another thing entirely. People here talk a lot about the measurements of their dicks, so it'd be good to learn a little bit about how the other puzzle piece fits.

    Here's the MRI study (linked from wikipedia) : http://www-psych.stanford.edu/~knutson/ans/faix02.pdf

    So the guy in this study was 16cm long erect (BPEL I believe after reading it.) That's about 6.3" long, so a fairly long fellow (who else would volunteer to get MRI'd during sex?) but more of a high average than a huge one.

    The whole thing's a good read, but here's some good stats to summarize:
    - 3cm (1.2") - dick remaining outside of vagina at apex of thrust in missionary. This isn't really just wasted in my opinion - the little bit coming out is still pushing against the labia + clit, so if you're super-girthy at the base then you've got that going for you.
    - 13cm (5.1") - amount of dick that actually gets in to the vagina
    - 7.5cm (3") & 11cm (4.3") - the length to the anterior fornix & posterior fornix (A-spot & cul-de-sac) before intercourse but after arousal
    - 13cm (5.1") - the length to both the fornices during sex. Basically, it stretches to fit the whole dick.
    - 9cm (3.5") - distance to the uterus during sex
    - The uterine position changes significantly on missionary vs doggy - on doggy, the uterus goes forward and down, while in missionary it goes up & backwards. I think this one's really interesting, since many girls remark that I go "way deeper" in doggy, yet due to my love of an ample bottom I'm sure I'm getting more dick buried in their thick butt. What's probably really happening is the cervix has just moved somewhere where it's closer to the front, so it feels way deeper.
    - The "impact point" (where most of your force of thrusting goes) is on the AFE in missionary, and the cul-de-sac + cervix in doggy. This again says a lot about feeling like doggy's a lot deeper, and explains why women's preferences vary a lot on position, since it's very different physical sensation.

    There's such an incredible amount of misinformation on this topic, with sites trying to sell big cock porn & dick pills (e.g. penissizedebate.com) acting like unless you're fucking with a thermos, a woman's just all empty space in there. It's good to see something more rigorous and accurate.

    Since women vary at least as much as men, these measurements don't apply for everyone, but I think serve as a useful baseline. This 6.3" guy is able to push well past his girlfriend's cervix, and compared to every accurate measurement study he's significantly bigger than average (at least one standard deviation above the mean.) It does take about 11cm to reach this woman's posterior fornix, and since you lose 3cm on the outside, that means you'd need a minimum of ~14cm (5.5") to reliably hit that cul de sac. That's pretty close to most medically verified averages (5.1"-5.5"), which makes total sense since men and women are supposed to fit together. I don't want to mix much anecdotal evidence in here, but this sounds right since many women (but not all) care a _lot_ more about having a dick that's a little longer than average (or just not too short), than they do about having one that's enormously long.

    An interesting thing to see in the diagrams is how good the uterus & cervix are at getting out of the way. If a 6.3" dick goes well past the cervix, then a lot of people could ram the cervix without really needing a very long dick. Hitting that thing is more about angle & position than anything else. [more anecdotes] - I had a girlfriend who I'd had regular sex with for months without any major problems (that couldn't be fixed with a little lube..); she complained that being on top made her legs tired, so she almost never did it. I finally convinced her to get on top one day, and she got on facing me but leaning way back. She had a quick sharp pain and flew off crying, and described it as like going to the gynocologist but much more intense.

    Anyway, maybe so much reality is out of place on a forum ripe with outrageous fantasies (e.g. "my wife wants to fuck my 15" friend", "I'm only 7" long - am I too small to please a woman?", etc.) but I just love numbers. Take a read and share your thoughts :)
     
  2. Meetmee

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    I've read this before. I'm glad that reading my post made you curious. That was my whole point. I know from my limited experience that women's bodies are very different. I Think that since there was only one couple in this experiment, that the results are less than conclusive. Just for full disclosure I am 7.5x6. I have found that just burying it to the hilt isn't enough. Indeed, if your dick is long enough, you'll just keep sliding right past those fornices without fully stimulating them. Maybe some women are sensitive enough that that's all it takes. Others may have smaller vaginas that receive enough stimulation from the unfocussed insertion of a large penis. For my wife, I have to get my penis at the right angle and apply steady pressure with short strokes, never taking my penis off the AF or PF. I guess I got lucky a couple of times over the years and hit the spots the right way by accident, but ramming away blindly usually wouldn't work. I can't imagine how limiting it must have been to try and have sex in that MRI chamber.
     
  3. B_Coconutz

    B_Coconutz New Member

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    Interesting study. Kinda mirrors the experiences I have had with ALL the women I have been with. One thing missing in the study is how the penis responds to pressure or bottoming out in the vagina. The head will compress, the shaft will slightly compress and bend or 'boomerang' more, and the base of the penis will be partially pushed back into the man's body. The longer the penis, the more these factors apply (moreso the bending). This would explain how some of the longer guys can get more in. Just physical engineering.:wink:
     
  4. ShannonH

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    Yeah the bending notion is kind of neat. I'm happy to have an upward curve in mine, and usually feel more like I'm getting even more curved as I stick it in.

    I think this study also really questions the traditional definitions of "bottoming out." Most guys are going to hit a "bottom"; you can hit the cervix more because of the angle than anything, so when most guys think they're "hitting bottom" and hurting their partner, they really just need to be more aware of the woman's body and adjust position.

    As much as we obsess about size, mainly because it's easy to measure, men and women are all different and this paper really shows that it's just as important how we fit together. Size is one factor, but shape and how that pressure gets applied makes a big difference. It's just one more factor you have no control over that you can worry about :)
     
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