The pubococcygeus (PC) muscles control urine flow and hold pelvic organs in place, but they're also the muscles that contract during climax. (businessinsider.com)
The intrepid participants start by inserting a jade egg tied to a light pouch full of crystals, and proceed to swing the pouches between their legs while clenching their pubococcygeus (aka the muscle you use to stop peeing). (health.com)
When you orgasm, a special area of your pelvic floor called the the pubococcygeus (PC) muscles contracts, leading to that big moment. (health.com)