US gymnast Simone Biles says she is still struggling with the 'twisties', raising doubts over her participation in her remaining Olympic finals.
The 24-year-old withdrew from the team and all-around finals in Tokyo, saying she was prioritising her mental health.
"I seriously cannot comprehend how to twist," she said during a social media Q&A session on Friday.
She is due to compete in all four individual apparatus finals, starting on Sunday.
The four-time Olympic champion posted videos on Instagram of her training session, in which she attempts twisting dismounts from the uneven bars but fails to land on her feet both times.
The gymnast said she had experienced the 'twisties' before but never on all four pieces of apparatus.
"It's never transferred to bars and beam before for me. It strictly likes vault and floor... the hardest two. But this time it's literally on every event. Which sucks... really bad."
She added that it could often take more than two weeks to overcome the issue.
The vault and uneven bars finals are on Sunday, with the floor event on Monday and the beam on Tuesday.
What are the 'twisties' in gymnastics?
Gymnasts have described the twisties as a kind of mental block.
In some sports a sudden mental block - like the 'yips' in golf - may cost you a missed putt, or a lost game.
In gymnastics, it can cause a person to lose their sense of space and dimension as they are in the air, causing them to lose control of their body and do extra twists or flips that they hadn't intended. In the worst cases, they can find themselves suddenly unable to land safely.
The twisties can happen to a gymnast even if they've done the same manoeuvre for years without problems.
Read more about the 'twisties' here.
Biles explained the struggles she is facing, saying: "It's honestly petrifying trying to do a skill but not having your mind and body in sync.
"I don't think you realise how dangerous this is on a competition/hard surface.
"Literally cannot tell up from down... I also have NO idea where I am going to land," she said. "Or what I am going to land on. Head/hands/feet/back."
Biles explained that the sensation began the morning after qualification, and in order to overcome it, she has to go back to the basics and do skills on soft surfaces and into pits to regain her confidence and air awareness.
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