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What are the 'twisties?' Simone Biles explains gymnastics struggle at Tokyo Olympics

It was “the strangest, weirdest feeling,” the four-time Olympic gold medalist told her followers on Instagram on Friday.

Simone Biles said she was still suffering with "the twisties” Friday and "literally can not tell up from down," raising serious doubts about whether she will be able compete in her individual events at the Tokyo Olympics.

Biles pulled out of the team all-around final Tuesday after struggling on her first routine and then withdrew ahead of Thursday's individual all-around final to focus on her mental health.

Suni Lee won gold in the event, defending the title for Team USA despite the reigning champion's absence.

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In a series of Instagram Stories posted early Friday, Biles invited her 6.1 million followers to ask about the phenomenon that can cause gymnasts to lose their sense of space and dimension in midair — even if they have performed the same maneuver for years without problems.

The four-time Olympic gold medalist also posted two videos of herself struggling with dismounts from the uneven bars. The first showed her landing on her back on the mat, the second showed her falling to the mat in apparent frustration after she still needed to complete another half twist.

She said the videos, which have subsequently been removed, were taken during practice Friday morning.

Biles, who appeared to become disorientated while performing a vault Tuesday before she stumbled on her dismount, said she had “no idea” how she landed on her feet.

“If you look at the pictures and my eyes, you can see how confused I am as to where I am in the air,” she told her followers.

The 24-year-old superstar is still scheduled to compete as an individual in the vault, bars, balance beam and floor exercise. The finals for those individual events are scheduled for Sunday, Monday and Tuesday.

Biles said that “the twisties” had “randomly started happening” the morning after preliminary competition, adding that it was “the strangest, weirdest feeling.”

She said she “literally can not tell up from down," which meant she had no idea how she was going to land or what part of her body she was going to land on. “It’s the craziest feeling ever," she added.

Getting rid of them “varies with time” and they had lasted for about two or more weeks in the past, she said, adding that they had “never transferred to the bars and beam before for me,” but this time it had affected her for every event “which sucks… really bad.”

Biles praised her teammates as “queens” for continuing without her in the team final and landing the silver medal. She also lauded Lee on Instagram on Thursday. "So so so beyond proud of you!!!" Biles said.

Addressing those who suggested she gave up by pulling out of the competitions earlier in the week, Biles said: “I didn't quit, my mind and body are simply not in sync.”

“I don't think you realize how dangerous this is on hard/competition surface,” she added. “Nor do I have to explain why I put health first. Physical health is mental health.”

She said she had “had plenty of bad performances throughout my career and finished the competition," but on this occasion she had "simply got so lost my safety was at risk as well as a team medal.”

While Biles' absence was felt on the floor of Tokyo's Ariake Gymnastics Centre, her decision to step back from competing to focus on her emotional well-being continued to make an impact across the sports world.

Her candid admission, which follows Naomi Osaka's decision this year to withdraw from tennis tournaments to protect her mental health, again put a global spotlight on the often taboo subject of mental health.