What are the twisties? How Simone Biles bounced back from the gymnastics phenomenon

Simone Biles is one step closer to her third straight Olympics, and it's been a long journey for the legendary gymnast over the last three years.

The seven-time Olympic medalist was looking to defend the individual all-around title at the 2020 Tokyo Games after winning gold in Rio four years prior. However, something was off by the time she started competing.

Biles realized she had the twisties and withdrew from the team final and individual all-around to focus on her mental health. She bounced back before competition ended, though, and walked away with a bronze medal in the balance beam to go along with silver in the team event.

On Friday, Biles will begin competition at the U.S. Gymnastics Trials with a chance to clinch her spot at the 2024 Paris Olympics. Before the event commences, here's a breakdown of the twisties and Biles' journey back to the top.

What are the twisties?

The "twisties" are a gymnastics phenomenon where an athlete suddenly loses their sense of where their body is in space. That sense is crucial in gymnastics, and the sudden loss of it could result in more than just a loss in competition, as it could lead to a serious injury or even paralysis.

Gymnast Laurie Hernandez, Biles’ 2016 Olympic teammate, told Olympics.com that the twisties can set in just as a gymnast attempts a high-level skill.

"The rhythm is off, and your brain will like, stutter step for half a second, and that's enough to throw off the whole skill," Hernandez said. "And, so, it happens, and it takes a second to get over that."

When did Simone Biles have the twisties?

Biles said she experienced the twisties more than two years before she withdrew from competition in Tokyo.

"2019, at the beginning of the year, I forgot how to twist and flip," Biles told Olympics.com in January 2020.

Once she got to Tokyo, Biles noticed she wasn't performing her vaults to her usual standard.

“It doesn’t feel comfortable, I have no idea where I am, but I’m twisting, praying I land on my feet,” Biles told Alex Cooper on an April episode of the "Call Her Daddy" podcast. “I felt like I was fighting my body and my mind to do these tricks.”

Biles cut herself and did not land steadily during her vault in the competition, only completing 1.5 rotations instead of the expected 2.5. From there, she did not return to competition until the balance beam final.

NBC Sports Gymnastics analyst Samantha Peszek previews the U.S. Gymnastics Trials.

What causes the twisties?

Biles said her twisties were likely caused by stress and other psychological factors.

"(The pressure) feels heavy," she told TODAY’s Hoda Kotb in 2021. "It’s like the weight of the world on your shoulders and I’m very small, so I feel like, at times, it’s very overwhelming, but whenever you get so overwhelmed and have triggers, it’s just like — I have to focus on my mental wellbeing and that’s what I did."

Aly Raisman, another member of the 2016 Olympic team, said Biles' unique level of difficulty could also have contributed to her getting "lost in the air."

"She’s doing such difficult skills, and she can twist so much more than the average person," Raisman Raisman told TODAY in 2021. She’s human. Sometimes it happens when you’re in the air, and we just kind of get confused.”

Has Simone Biles recovered from the twisties?

Biles returned from the twisties during the Tokyo Games to earn bronze in the balance beam. Now, she's poised to earn more hardware in Paris.

"I'm fine. I'm twisting again," Biles said last year. "No worries. All is good."

The 27-year-old is coming off her ninth career national championship as she heads into the U.S. Gymnastics Trials in Minneapolis on Friday. She can automatically qualify for the 2024 Olympics through the trials, and Team USA's Olympic committee will select four more women's gymnasts to assemble Team USA for Paris.