The rest, Coichetti said, is all physics, and it boils down to F=MA.
"When I have a pulley system on a ceiling, if you weigh 100 pounds, I have to exert 100 pounds to lift you off the ground," he said. "Now, you also have motion. You have to figure out the angle of motion, the rate of acceleration. I do it in my head. I have to figure out how much stress you are putting on the top rig, on the pulley, on the rope, on your hooks, on yourself, and I have to make sure everything is within a correct range."
To more easily hoist the weight of a human body, suspension artists make use of mechanical advantage, rigging up complex pulley systems that facilitate the raising and lowering of the suspended person. Coichetti once rigged a woman in a marionette suspension, where hooks were inserted on the woman's back, into her legs, and into her arms, so that the woman was suspended as a living, breathing marionette controlled by Coichetti with the movement of his hand and arm.
"I had to figure out a way to attach all her points to a glove," Coichetti said. "So that going like this," he moved two fingers up and down as if playing a piano, "would raise her left arm, would raise her right arm. And I had to rig it all so that just three inches of motion would create four feet of motion on her side." Moving his arm up and down lowered and raised the woman.
He acknowledged, though, that he had a little help with lifting the woman's limbs with his fingers--most people, he said, when they feel a hook pulling on their arm tend to raise their arm along with the upward pull.
The most visibly jarring thing about watching a suspension is seeing flesh stretch as it supports the weight of the body. It looks like it's about to rip -- sending the suspended person falling to the ground amidst a confetti of torn flesh and blood -- but it's actually quite safe. During a suspension, hooks are inserted under the dermis and into the subcutaneous fatty tissue, a very resilient chunk of flesh.
"Skin is pretty strong," Dr. Nelson Goldberg, a plastic surgeon at the University of Maryland Medical Center, said. "It's basically leather, and in the back it's basically double leather. I think it could easily handle the tension before it would rip."
Dr. Brett King, an assistant professor of dermatology at the Yale School of Medicine, sees suspension as an application of physics and a testament to the human body's remarkable toughness and healing ability.
"You're putting your body's weight worth of force across that tissue," King said, "and it's quite striking that the skin holds up as well as it does. My guess is that, whether or not the practitioners of suspension realize it or not, the people who plant the hooks in the skin understand that there's a tremendous amount of physics to all of this. They must use hooks that are appropriately thick to hook an appropriately broad swath of skin. You can imagine, if you were to take something as thin as a slim nail and kind of loop it under the skin and back out, and then pull the two ends away from the body, it might very well rip the skin. Alternatively, if a much wider nail or hook is sewn underneath and back out across a wide enough section of skin, then suddenly there is enough fabric to support the weight. It's a calculation that involves the total dimension of skin across which you're supporting some amount of weight."
"It's kind of dazzling," he said, "to conceive the entire body's weight being supported by a couple of hooks through the chest."
"It's pretty cool," he added.
When I asked Coichetti to describe the sensation of being suspended, he said, "It's this odd pressure, and it almost feels like--" he paused, thinking. "Do you ever stand in the sunlight, like at the beach, and, not that it hurts, but you can feel when you're burning? Like, 'Aw, man, I can feel the heat. I can feel myself burning. I know I've gotta get out of the sunlight.' That burning sensation. You feel that. It's not painful, but you definitely feel burning. And you feel this odd pressure happening. Once you're in the air for, like, 30 or 40 seconds, that burn fades away. And then you get hit with the euphoria. You still feel the pressure, but at that point in time, you're elsewhere."
"Grab the meat of our best friend's back and just yank up really hard," AJ Karras suggested. "Try to pick them up, too."
Karras, a young woman with pink hair, came to New York City from outside Amherst, Massachusetts, to be suspended for the first time by Coichetti. She was excited, and her boyfriend had come with her for his first suspension, too. Karras has been involved in the body modification scene for about five years, and has been helping out with suspensions and heavier body modifications, mostly types of cosmetic implants, for the last two.
"I saw suspension videos when I was 15 years old," she said, "and I was like, 'Dude, I have to try that. I just have to.' I just always knew that it was part of me."