TOKYO — Imagine flying through the air, springing off a piece of equipment as you prepare to flip on one axis while twisting on another. It all happens fast, so there's little time to adjust. You rely on muscle memory, trusting that it'll work out, because with so much practice, it usually does.

But then suddenly, you're upside down in midair and your brain feels disconnected from your body. Your limbs that usually control how much you spin have stopped listening, and you feel lost. You hope all the years you've spent in this sport will guide your body to a safe landing position.

When Simone Biles pushed off the vaulting table Tuesday, she entered that terrifying world of uncertainty. In the Olympic team final, Biles planned to perform a 2½-twisting vault, but her mind chose to stall after just 1½ twists instead.

"I had no idea where I was in the air," Biles said. "I could have hurt myself."

Biles, who subsequently withdrew from the team competition and then the all-around final a day later, described what went wrong during that vault as "having a little bit of the twisties."

The cute-sounding term, well-known in the gymnastics community, describes a frightening predicament. When gymnasts have the "twisties," they lose control of their bodies as they spin through the air. Sometimes they twist when they hadn't planned to. Other times they stop midway through, as Biles did. And after experiencing the twisties once, it's very difficult to forget. Instinct gets replaced by thought. Thought quickly leads to worry. Worry is difficult to escape.

"Simply, your life is in danger when you're doing gymnastics," said Sean Melton, a former elite gymnast who dealt with the twisties through his entire career. "And then, when you add this unknown of not being able to control your body while doing these extremely dangerous skills, it adds an extreme level of stress. And it's terrifying, honestly, because you have no idea what is going to happen."

The twisties are essentially like the yips in other sports. But in gymnastics, the phenomenon affects the athletes when they're in the air, so the mind-body disconnect can be dangerous, even for someone of Biles's caliber.

After Tuesday's team final, Biles described mental health challenges that went well beyond gymnastics, with roots in the overwhelming pressure to perform as one of the faces of these Olympics and in the stresses of the pandemic year. Her experience with the twisties is impossible to separate from those broader issues, and regardless, it's irrelevant to the dangers posed by them.

Biles had started to have trouble with some skills leading up to these Games. Fellow Olympic team member Jordan Chiles, who trains with Biles in Spring, Tex., said Biles had been "giving us a little heart attack."

Biles performs some of the world's hardest skills, including a double-twisting double tuck dismount off beam and a triple-twisting double tuck on floor. To execute those elements safely, Biles said, "you have to be there 100 percent or 120 percent, because if you're not the slightest bit, you can get hurt." As a 24-year-old veteran, Biles realized she might not have been able to regain that mental fortitude.

When Biles mentioned that she had struggled with the twisties, former gymnasts flooded social media with empathy. Some detailed injuries they suffered after getting lost midway through a skill. One person called the twisties the "the scariest, most uncontrollable sensation."

"It's like a nonserious stroke," 1988 Olympian Missy Marlowe tweeted.

Ariana Guerra, a former U.S. elite gymnast, dealt with the twisties multiple times during her career. At one point, she trained a double layout on floor and that same skill with a full twist during the second flip. She needed to warm up the double layout first and would worry that she would twist accidentally. The trouble spiraled, and soon, she couldn't perform a simple back tuck without twisting. She worried about how the twisties could spread to skills on other apparatuses.

Guerra would go to the trampoline and tell herself: "Just a back handspring. Just a back handspring." At the last second, she'd pick up her hands so they didn't touch the ground. That was the only route toward performing a flip without her body adding an unintentional twist. After practice, she would do backward rolls — a skill that preschoolers learn — in hopes of regaining that feeling of only rotating without spinning.

"That's how mental it was," Guerra said.

It took about two weeks to overcome, Guerra said, and she was in the midst of her preparation for an important competition. She thinks the twisties are more likely to surface during moments of stress.

Melton had the same issue in which his "body, for some reason, just automatically starts twisting and you just have no control over it." Then, rather than focusing on technique, he'd start thinking about the twisties, which would lead to more trouble. At one competition, when Melton saluted the judges and looked down the runway, he couldn't remember which direction he twisted on his new vault.

For Melton, the twisties turned into a recurring problem. He eventually tailored his routines to include skills that didn't lead to getting lost in the air. "There was no point in trying to fight the twisties at that point in my life," said Melton, who recently retired from the sport.

Earlier in his career, Melton's coaches would have him progress through basic elements — first a back tuck, then a back layout, a half twist and a full. But doing so took time. And at his gym, Melton could use the pits to eliminate the risk of injury while he focused on working through the issue.

"But when you're at the Olympic Games, you don't have that luxury of training in a facility where you can take a day to do basics, re-control your gymnastics and go into pits," Melton said. "It's tough when you're at a competition and you're dealing with it, because the stress of the competition's weighing on you."