US gymnastics star Simone Biles will not defend her Olympic gold medal on floor exercise. The announcement on Sunday from USA Gymnastics came a day after she withdrew from the vault and uneven bars finals at the Tokyo Olympics.

Biles withdrew from the gymnastics team event on Tuesday and later decided not to compete in the all-around event, citing a need to focus on her mental health.

It remains to be seen whether she will compete in two remaining gymnastics finals that are slated to take place next week.

What is the latest?

"After further consultation with medical staff, Simone Biles has decided to withdraw from the event finals for vault and the uneven bars," USA Gymnastics said in a statement.

"She will continue to be evaluated daily to determine whether to compete in the finals for floor exercise and balance beam."

The US gymnastics body said it continues to stand behind Biles amid her recent battles with mental health.

"We remain in awe of Simone, who continues to handle this situation with courage and grace, and all of the athletes who have stepped up during these unexpected circumstances," USA gymnastics tweeted.

The US gymnastics federation said that MyKayla Skinner would replace the defending champion in the vault final alongside team member Jade Carey.

Skinner later tweeted that she "can’t wait to compete in vault finals. Doing this for us @Simone_Biles. It's go time baby!"

Why did Biles pull out?

Biles said on Friday she was struggling with the "twisties," a mental block where she "can not tell up from down."

She explained: "the strangest, weirdest feeling" of not being able to do basic twists on her Instagram feed followed by over six million fans.

One of the Instagram posts featured a video of Biles landing on her back in training while being visibly frustrated, She later removed the posts. 

"It's honestly petrifying trying to do a skill but not having your mind and body in sync," Biles added.

Canadian gold-medal-winning trampolinist Rosie MacLennan said she got the "twisties" while training for Rio 2016, having to relearn a lot of her technique from scratch.

"There (are) mental pieces to all sports, but in aerial sports where you're slipping and twisting, there's a huge mental component," MacLennan said on Friday in Tokyo.

"When you get lost in the air, it's one of the most terrifying experiences you can have."

jc/rs (AFP, Reuters)