Simone Biles might have made it seem too easy to fly through the air. It’s not, a fact that Simone Biles and other gymnasts have long known.

No matter how simple the leap may seem, it requires an intuitive sense of time and place. It is important to be able to calculate how much time it takes for your body to perform the task. You must also know how much time you have to accomplish it before the ground gives you a verdict.

Simone Biles was undefeated for eight consecutive years. Gravity is always-and-0.

The four-time Olympic gold medalist, who qualified at the Tokyo Olympics on Sunday afternoon, lost her way. She kept telling her body that it was time to turn. It kept repeating, “How about no?”

They were called the “twisties” in the gymnastics world. And Biles knew it, leading her to withdraw from the team final after one rotation and skip the all-around final. She watched from the stands on Thursday as U.S. teammate and good friend Sunisa Lee claimed the gold.

Biles isn’t ruling out the possibility of competing in finals for each event — she’s qualified to compete in all four — which will be held starting Sunday. But even a brief break from the competition floor hasn’t helped her. During a series of social media posts on Friday, the 24-year-old provided an inside look at the “twisties.”

So, WHAT ARE THEY?

Twisties are sudden inability of a gymnast make the required spins, or any spins, for a particular maneuver.

Biles uploaded a video of herself doing a dismount on uneven bars during training. She later deleted it. Biles kept failing to complete 2 1/2 twists. On Tuesday night, she also failed to complete an Amanar vault. She had to abandon the competition after coming up short by one twist.

“Sometimes I can’t even fathom twisting,” Biles posted. “I can’t even understand how to twist,” Biles stated.

It was described by her as the “strangest, weirdest thing”

WHY DO THEY POP-UP?

Nobody knows. None, not even the greatest. Biles claimed that the “twisties”, despite some mistakes during qualifying, didn’t appear until Monday.

They’ve dealt with her before. What’s the difference? They aren’t just affecting her on floor and vault, as they did in the past. They’re now following her to bars, beam, and floor exercise, as well.

She wrote that it was “truly terrifying” to try to master a skill while your mind and body are not in sync.

HOW LONG WILL THEY LASTEN?

It all depends on the athlete. Biles can wait for up to two weeks, so her availability for the event finals is unlikely.

Rosie MacLennan, a Canadian trampolinist who has twice won gold at the Olympics, struggled to overcome her “the twisties” during training for Rio de Janeiro 2016. Although she was able to recover in time to reach the top of the podium in Brazil after a lot of hard work, it took her a while to re-learn her skills.

After finishing fourth, MacLennan stated that there are mental components to all sports. However, aerial sports which involve slipping and twisting have a significant mental component. “It’s one of most frightening experiences you can have, especially when you get lost up in the air.”

The terror that never truly goes away.

MacLennan, 32 years old, said that “it sticks with you.” It’s something you have to do, even if you don’t think so. It takes hard work, patience, and support from others.