People walking through the Diag on a Wednesday evening may not have noticed, but Nate Juliar was suspended upside down twenty feet above the ground, his legs spread apart, blood draining to his head, grinning. He’d wrapped his torso and feet in the green fabric hanging down from a large oak branch. As he hung there, Abby Rudnicki gave his brother, Ben, a leg up to grab on to Nate’s hands. Ben secured his own feet in the fabric, legs sprawled. They hung on to each other, swaying slightly in the wind, until Ben let go and they dismantled, laughing.

The three were the first to arrive to the weekly meeting of aerial silks performers, a group formed a few years ago by locals Irene Cameron and Justin Tesmer.

The sport is thought to have begun with circus performers in Montreal in the 1980s. Despite the name, the fabric is mostly nylon or polyester, not silk.

Silks are a demanding art form. Rudnicki “considered myself active, but after a whole day of practicing, the next day, everything from the neck down hurt. I mean everything,” she says. Most of the strain is on the core and upper body muscles, and—something that not a lot of people think of—the fingers. A lot of newcomers make the mistake of using arm strength to position themselves, but it’s easier to use leg muscles.

The group tries to meet Wednesdays at 5 p.m. on the Diag when the weather’s nice. An average turnout is about ten to twenty people, but passersby often stop and watch—some of the brave ones even give it a try. Most participants are in their twenties, but there have been nine-year olds and some adults middle-aged and up.

Silks culture thrives on sharing knowledge; there’s an expectation that you’ll pass on whatever you know to the next person who wants to try.

Cameron talks U-M student Christine Alexander through a trick; Alexander has been up before, but wants to go higher this time. She climbs halfway between ground and tree limb, then wraps herself securely in the fabric. When she looks down, she laughs. “Oh I’m so high. Wow, that’s scary!” A moment later, “Oh, this is fun, I like being up in the air!”

Carefully studying Alexander’s position, Cameron tells her she can let go. When Alexander loosens her hold, the fabric gives a little but she remains safe in the air. After a few moments, she drops onto the tarp on the ground, grinning. Alexander later teaches the move to Rudnicki.

Most tricks consist of climbs, wraps, or drops. There’s no universal lingo—it’s regional, and people make up their own names. A lot of the terms Cameron uses come from yoga, like “pigeon” and “scorpion.” A move in which the climber falls a few feet after securing his or her torso and ankles, which many people call the “butterfly drop,” she calls “flailing cricket” because it “can be so awkward for new people.”

Cameron once broke her hand when she tried to create a new trick. But generally, she says, safety is not really a problem. If you fall, it’s probably slow, and “usually something will catch you,” she says. “It’s not common to just fall. Most people know their strength.” They might also set up mats underneath the performer or ask for a spotter.

The group seems to thrive and grow on curiosity and surprise alone. “It’s an interesting bridge between something a lot of people would never think they can do, and something they can just try,” Cameron says. Adds Tesmer, “It’s really awesome to see someone make the transition to ‘Oh my God, I can actually do this.'”