The Truth:

Come on! That can't be true, right? It's not like a boner has an actual bone in it.

No, but there are two cylinders of tissue that become rigid during an erection, and if she lands on it wrong, it can break, with "an audible cracking sound."

And strangely, this is more likely to happen when a man is cheating, according to University of Maryland Medical Center researcher Dr. Andrew Kramer, who studies penile fractures (and incidentally has by far the worst job in the world). Kramer's research shows that when a man is having an affair, he's more likely to end up with a sharp 90 degree bend in his Mini-Me. He reasoned that illicit sex is more likely to happen in unusual ways or places -- the guy is trying to impress her, after all -- and it's awkward positions and "acrobatic" sex that create the most danger to his brittle love stick.

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"So did you want me to straighten it back out or break it again and give you the Lightning Bolt Special?"

Incidentally, if this ever happens to you or someone you love, yes, you need to seek medical attention immediately. Fixing a break probably requires surgery. If you're embarrassed, just emphasize to the doctor how acrobatic the sex was.

The Myth:

"I heard from a friend of a friend about this guy who was banging some married chick. The husband came home without warning, and the dude tried to pull out and run away, but he couldn't. He was stuck. Inside her."

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"And don't think I didn't notice the WD-40 on your pants, too!"

The Truth:

It sounds like the dumbest of the sex horror urban legends, but sometimes even the dumbest stories have a kernel of truth to them. In this case, it's a rarely documented but not unknown phenomenon called penis captivus. You don't need to be fluent in Latin to guess what that means. For instance, doctors at a British hospital reported a young couple being brought in via ambulance and carried into the emergency room on a single stretcher, as they were stuck together like conjoined twins joined at the genitals. Once inside, they were presumably pried apart with a crowbar, making a kind of cork popping sound when they disengaged.

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... goes your weasel.

Legends of people getting their dirty bits stuck inside each other have persisted for centuries, and it was long said that it happened when people did the nasty with someone they shouldn't, like another man's wife. Modern medicine dismissed the idea for a long time, chalking it up to a hilarious scary story told to keep people from cheating on their spouses.

But medical science is always trying to discover new horrors for you to have nightmares about, and now experts say all it takes is for the female's southern regions to clench in such a way as to turn a vagina into a kind of Chinese finger trap. If you would like an illustration, go to YouTube and browse the many, many videos of it happening to dogs:

"Dude, c'mon on. Little privacy?"

Or don't. There are better uses of your time. Anyway, humans aren't dogs, and when this happens to us, it's usually only for a few seconds, and then everyone has a good laugh about it. Usually.

The Myth:

"Dude, my bro was railing this chick and he busted his nut so hard, he went blind! Said it was totally worth it, though."

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"Doggie style and a dog. Win/win."

The Truth:

Despite all those crazy liars telling you that masturbation is completely safe, your mom may actually have been right when she told you that flogging the dolphin would make you go blind. Well, kind of. It turns out that it is possible to have an orgasm so aggressive that you straight up lose your vision.

The blindness, known by the terrifying name of amaurosis fugax, usually only lasts for a few minutes before your sight comes back. And, bizarrely, it only happens in one eye, for some reason. When a 52-year-old man started going blind every time he had sex with his wife, he decided he should probably see a doctor. So did a Danish man and a woman from Texas. They made the right choice, because suddenly losing sight while working hard is a classic stroke symptom.

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No, not that kind.

In each case, the blindness was experienced right around the time of orgasm. When given a stress test on a treadmill, the patients were just fine -- it was only sex that set off the condition. And it isn't necessarily a one-time thing. In the case of the 66-year-old Danish guy, he'd been going blind two or three times a week, which is actually kind of admirable when you consider his age and realize he considered his vision less important than poontang.

Doctors aren't sure why it happens, but it's theorized that a particular kind of exertion that some people tend to put their bodies through at the point of orgasm can dam the blood vessels in the eye (some of the patients were cured by prescribing them blood-thinning medication to take before sex). You should also note that this is yet another reason not to have sex while driving or flying an aircraft.

"Holy shit, tell him not to do that, man! I met this kid at camp whose friend did that and died."

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Which still barely cracks the top 10 of disturbing vacuum cleaner sex tricks.

The Truth:

In case you don't know, a hickey, or love bite, is a sign of affection whereby your partner puts their mouth on your neck and sucks so hard that it leaves a long-lasting mark. Yeah, it's actually pretty fucking weird when you see it written out like that, but what's weirder is the fact that it can apparently give you a goddamn stroke, which is even less romantic.

A Maori woman from New Zealand freaked out a little when her left arm suddenly stopped working one day. Needing her arm to do various arm-related things, she decided she should hit up the local ER. When the doctors looked her over, they decided that she'd had a stroke and gave her some blood thinners as part of the standard treatment, although they had no idea what might have caused a healthy woman to stroke out like that.

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No, not that kind, either.

But then one of them noticed a bruise on her neck right next to a major artery. The woman told them it was a hickey, presumably rolling her eyes at the clueless nerds. But when they examined it closer, they discovered that the woman had been hickeyed so hard that it had bruised a major artery, which clotted to the point of stroke and potential paralysis. Doctors could find no other recorded examples of this happening, although obviously that doesn't mean it hasn't happened -- it's not like this is the first thing they check for on stroke victims.

Just ask the British woman who had what might be the first recorded case of a sexually transmitted allergic reaction. Her boyfriend ate a few handfuls of mixed nuts, but, knowing about his lady friend's debilitating Brazil nut allergy, he showered and brushed his teeth before making his move. Still, after they finished up, the woman began to experience the tell-tale signs of having ingested nuts, and not the kind of nuts that she thought she'd had in her mouth. After going to the doctor, their fears were confirmed when the doc did one of those skin-prick tests with his nutty semen.

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"Judging by the giggling coming from the lab, I'm pretty sure your results came back positive."

That's right -- in what must have been the most awkward hospital visit of all time, the doctor asked him to eat some Brazil nuts and then rub one out into a vial so that he could smear it on his girlfriend's arm, at which point he would have been right to ask whether he could check the guy's medical license.

The Myth:

"You'd better be careful if you're thinking of cheating on that nice girl, because karma will always catch up with you in the end. Death karma."

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The kind terrible Seagal movies are named after.

The Truth:

We mentioned earlier that boner fractures are more common among unfaithful partners, due to the "Let's try it on my motorcycle!" nature of the sex they're having. But it turns out those guys are getting off easy.

People have been spreading urban legends about infidelity causing death since time immemorial. It's easy to see why -- there's no better way to discourage immoral behavior than to perpetuate a rumor that God will strike you down for it. But surely, as far as biology is concerned, there shouldn't be anything dangerous about infidelity, because it's not like nature cares whether you and the person you're boning have matching rings, right? Well, here's where things get weird.

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Weirder, anyway. These are usually some off-the-menu hijinks to begin with.

Sure, people just stop being alive during sex sometimes. That's not really news, since TV and movies have been playing the "old man dies on top of his young girlfriend" bit for years. Studies report that roughly 1 percent of sudden deaths happen during some bedroom hanky-panky. But here's the thing: Of that group of people, almost all of them were cheating on their significant other.

That means that if you're getting some on the side, you might want to make sure you lay off the pork rinds and go for a jog once in a while. Also, some sad news for cheating d-bags everywhere: The fatalities are almost exclusively dudes. Although they were usually with a much younger woman, so we guess that's a trade-off you've got to choose for yourself.

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"He died as he lived: drunk under some woman he met on Craigslist."

As you can guess, the logic is similar to the penis breaks -- those older guys in full midlife crisis mode are trying to go extra hard, while also feeling the fear of getting caught and the excitement that comes with banging a secretary in their office. That winds up being a little too much for the ol' ticker (or whatever other organ was the weak link in their system), and before they know it, they've humped their way right off the mortal coil. We'd offer some word of caution here, but it's not like it would actually stop anyone, right?

Aaron Granger is a chemist and likes to write about science projects in his spare time. He updates his website, Impractical Science, roughly whenever.

For more on bumping genitals together, check out The Sex Ed Lessons You Wish They'd Taught You.

Related Reading: Cracked has plenty of sex myths to bust, too. Married people don't have less sex. But hey, some people totally do get their dicks stuck in pool filters. For a scientific explanation of the 'beer goggles' effect, click here.