Whether you’re a Kama Sutra advocate, a fan of Tantric antics or you just like to twist torsos into standard sexual positions, you’ve probably put the boundaries of human agility to the test on more than one occasion. Unlike the rest of the animal kingdom, humans like to explore all kinds of sexual positions. But if your luck runs out somewhere between the first exciting sensations of foreplay and the final throes of orgasm, you could soon learn why most animals favor doggy-style.

All it takes is a slight misjudgment of rhythm (you zig, he zags) and you could go from being ridden cowboy-style to taking a ride in an ambulance. Many a man has found himself hobbling into the ER with a seriously twisted piston.

The erect penis operates on a principal similar to a mechanical crane. Having received a message of erotic stimulation from the nervous system, the two sponge-like penile chambers called corpora cavernosa begin filling up, causing the phallus to thicken and rise. A strong attachment coming from the corpora chambers then works like an anchor, steadying the erect penis and preparing it for insertion. In the case of blunt trauma, this attachment—along with other parts of the penis—can be damaged.

There are generally two positions that are the riskiest for sex—standing while cradling your lover and the dual sitting position. The former might make you feel like your lover’s own personal superhero, but if your grip slips, you’ll discover that that the term “love muscle” is just a cliché.

The other perilous sex pose, the dual sitting position, is fine unless you slip out and come down hard on the tip of his schlong with your pelvic bone. If it does happen, with strong pressure your lover could experience a penile fracture. You’ll know this is the case when you hear a loud pop followed by an even louder scream.

Every year, according to hospital records, about 1,000 men across the United States stumble into emergency rooms with just such injuries. But according to Dr. Stephen Lamm, clinical assistant professor of medicine at New York University and author of The Hardness Factor, this figure is distorted by humiliation. “Penile fracture is fortunately uncommon, but more common than is actually reported because people are embarrassed about it,” says Lamm. “If this happens to you, don’t be embarrassed. Make sure you get medical attention right away, because it’s an overwhelming likelihood that you’re going to need surgery.”

So go forth, you proponents of alternative positions and enjoy the fruits of human nimbleness. Just remember that your carnal calisthenics never come without some degree of disabling risk.