Upon first observation, the human butthole does not seem capable of fitting an entire fist. This is a common challenge for all great architects and engineers striving to fit a square peg into a round hole. The science of fisting is similar to the popular misconception that a bee’s body is much too fat to be able to fly with those tiny little wings — yet bees do fly. They don’t violate any laws of aviation. Their wings generate the perfect balance between lift, drag, weight and thrust. In the same way, a hand all the way through a sphincter does not defy science or anatomy, it just might take some extra work.
Newton’s second law of motion says that force equals the mass times the acceleration of an object. If the average mass of a human hand is 0.61 kilograms and the acceleration into the anus is a gentle 0.01 meters per second squared, then the force exerted on the hole is 0.0061 Newtons. If you are fisting with a physicist, they might calculate this before you oil up and dive in, but what matters is that you are exerting just enough Newtons to the butthole to penetrate, but not to tear the tissue.
Especially if you are just starting out, it is important to fist with your hand in the shape of a cone. The cone can be made by holding your fingers together at a point, the pinky and index finger meeting beneath the middle finger. This is so that the penetration is skinnier at first and works its way up to the meaty thickness of the fist. Once the knuckles are in, the anal cavity forms neatly around the rest of the hand. This way, fisting is not like sticking a square peg in a round hole, but rather like sliding a leg into a pair of extra small, wet yoga pants.
In physics, kinetic friction is the force that resists the movement of an object once it’s in motion. Changing the roughness of the surfaces rubbing against each other will increase or decrease the amount of kinetic friction. You can describe the roughness of a surface using a coefficient of kinetic friction which quantifies the roughness of surfaces like wood or cement. For the skin of a hand against the inner lining of an anus, the kinetic friction coefficient is often too high for smooth sailing, so lube is essential. Lubrication lowers the heat and roughness between two surfaces by creating a slippery film between them. Some sex shops even sell latex fisting mittens so you don’t have to constantly apply lube, and the latex barrier protects your partner’s insides from unclipped fingernails.
When you are wrist-deep in someone, small movements feel monumental. There is an exponential magnitude to all sensations. Wiggle ever so slightly, and they will feel a seismic event. Gentleness is the name of the game, so it’s nothing to be ashamed of if you can’t get the fist in as far as you would like, even if it isn’t your first time. If you want to know how far your anus or vagina will stretch, you can calculate the elastic modulus, which is equal to how much stress is applied to the hole divided by the strain you are inflicting on it. This way, you could calculate the potential energy stored in the sphincter when you put your fist through it. Figuring this out might turn the bedroom into a laboratory, since it requires measuring force divided by a cross-sectional area as well as finding the change in the hole’s length divided by its length before you fisted it. I highly recommend this for anyone whose kink is science. You might just win a Nobel Prize.
Fisting brings order to our chaotic world. It is one of the times when things can fit inside each other with great pleasure. It’s the relief of discovering lubed ease when you expect to struggle, and having your favorite orifice filled to its quivering capacity. It’s akin to when Einstein penned his theory of relativity, turning a concept like mass and energy being interchangeable into a simple yet abstract equation: orgasm equals fist plus anus squared.
Anya Neeze is a student at Cornell University. Comments can be sent to [email protected]. Boink! runs during alternate Sex on Thursdays this semester.