TOKYO—Simone Biles used social media on Friday to document in detail the harrowing condition that prompted her dramatic withdrawal from gymnastics team and all-around competitions at the Tokyo Olympics earlier this week. 

In an Instagram story of more than a dozen posts, she indicated that the condition—which gymnasts call “the twisties”—persists and her status for individual apparatus finals at the Games remains uncertain. 

However, Biles also asserted that she remains committed to a 35-city “Gold Over America Tour” of exhibition performances that is scheduled for this fall in the U.S. 

The 24-year-old directly said for the first time that she believed she had a condition that gymnasts called “the twisties”—described by them as a sudden onset of disorientation in the air that causes them to lose skills they have comfortably performed for years, with potentially catastrophic consequences.

Simone Biles’s withdrawal from competitions at the Tokyo Olympics has put renewed focus on mental health in sports. WSJ looks at how the stigma and treatment for athletes’ state of mind has shifted. Photo: Mike Blake/Reuters

Biles posted videos of herself crashing off the uneven bars onto practice mats in an attempted dismount, which she said had been taken from her practice Friday morning in Japan.

“For anyone saying I quit,” she wrote. “I didn’t quit…as you can see here. I don’t think you realize how dangerous this is on hard/competition surface…I’ve had plenty of bad performances throughout my career and finished the competition.”

The problem has not gone away following her withdrawals this week and extends to all four apparatus. She said in the Instagram story that she has experienced the problem before on the vault and floor exercise, the most fear-inducing events because of the speed at which she is moving, and that it had never before transferred to the uneven bars and balance beam.

“But this time it’s literally on every event. Which sucks. Really bad,” she said.

Biles described a terrifying loss of control under the grip of the condition.

“Sometimes I can’t even fathom twisting,” she wrote on Instagram. “I seriously cannot comprehend how to twist…. It’s the craziest feeling ever. Not having an inch of control over your body. What’s even scarier is that since I have no idea where I am in the air, I also have NO idea how I’m going to land. Or what I’m going to land on,” she said. Biles added that landing on her head was one possibility. 

A broad array of international gymnasts and coaches have affirmed the existence of “the twisties,” described their own experiences with them, and said that if Biles had them, she had made the right decision to withdraw from the team event after her first, frightening vault. 

Those gymnasts included 2012 Olympic U.S. star vaulter McKayla Maroney, but also Russians such as the individual all-around bronze medalist in Tokyo, Angelina Melnikova, and Svetlana Khorkina, a highly decorated gymnast who has rarely been complimentary of Biles in the past.

By removing herself from competition, Biles immediately became a cultural flashpoint back home: lauded by some for consciously removing herself from a dangerous situation, and accused of selfishness or fragility by others. 

In a stretch of dominance that goes all the way back to 2013, she has racked up an insurmountable lead in competition over every gymnast in large part because of her ability to execute more of the most complex skills—in which she both turns and twists in the air more and better than anyone else.

Simone Biles stumbles upon landing after competing a vault.

Simone Biles stumbles upon landing after competing a vault.

Photo: Jamie Squire/Getty Images

Academics who have written about yips and “lost movement syndrome,” likening them to “feeling like someone, or something, other than the athlete was in control for a momentary period of time.” Maroney said that in her experience, they had occurred when she was depressed, or doing too many different skills, but that they could also appear out of nowhere. 

Biles said on Instagram that they “could be triggered by stress I hear, but I’m also not sure how true that is.”

She said she had not been having the problem before she left the United States, that it “randomly started” the morning after Sunday’s qualification round, in which a set of subpar performances by the United States left them in a surprising second to Russian gymnasts.

“An alternate was not allowed to be placed in my position, for you ‘know it alls’,” she wrote. Biles also said she had tried to push through ahead of the team final—warming up “ok-ish.”

She added: “I chose not to continue team competition in jeopardizing losing a medal (of any color) for the girls/US” and “also for my own safety and health.” After her withdrawal, teammate Jordan Chiles performed on bars and balance beam instead, and Sunisa Lee on floor, their scores securing a silver medal for the U.S.

She said she was trying to unlock herself in Tokyo by practicing with soft surfaces and foam pits, but that in the past, it has taken two or more weeks to get rid of the condition. “Something you have to take literally day by day, turn by turn,” she wrote, indicating that there is a strong possibility that she will not be able to compete in Tokyo on any of the four apparatus finals for which she has qualified. 

Biles is set to headline the tour in the fall, becoming the face of a post-Olympic event that was previously operated in the name of USA Gymnastics, the federation with which she has a strained relationship.

The tour has been billed as the “Gold Over America Tour Starring Simone Biles”—a play on Biles’s ‘greatest of all time’ moniker and the 23 Olympic and world gold medals she already holds. But that billing also anticipated she could bring home as many as five more from Tokyo.

Simone Biles and Grace McCallum watch as Jordan Chiles competes on the uneven bars.

Simone Biles and Grace McCallum watch as Jordan Chiles competes on the uneven bars.

Photo: Jamie Squire/Getty Images

Tour organizers will now have to promote the tour around the dramatic upsets in Tokyo — including the women’s team’s silver medal she shares. Lee also went on to win gold in the individual all-around on Thursday, continuing an unbroken line of champions for the U.S. stretching back to 2004—and Biles was cheering her on in person and on social media.

Biles said that she did not believe “the twisties” would prevent her from performing on the tour because she had in mind a “simple fix”: she can adapt her routines on tour if necessary, even avoiding twisting entirely if it were to still be a problem. 

“Unfortunately in my Olympic routines I do a ton of twists on each event,” she said.

Write to Louise Radnofsky at louise.radnofsky@wsj.com