Los Angeles, Aug 14 (AFP) Simone Biles continues to push the boundaries of her sport to the point even the American gymnast's rivals can only watch in admiration.

Sunisa Lee said she was "super happy" to take the all-around silver medal at the US championships this weekend, where Biles capped her record-tying sixth national all-around title with a never-before-seen "triple-double" floor exercise landing -- a finale featuring two flips and three twists.

Even Biles admitted she couldn't wait to see the replay of the move, whipping out her phone between rotations to check out the video.

"I didn't want to be the last person to see it," she said.

Biles -- who already has a vault skill and a floor exercise maneuver named for her as their originator -- pressed the limits in balance beam in Kansas City, too, with a double-flip, double-twist beam dismount.

Lee was more than content with her silver, while Morgan Hurd, who finished fourth, called Biles "superhuman".

"I do consider it a win, just because she's unbeatable," Lee said. Biles' performance in Kansas City was a glimpse of what she has in store for the World Championships, which are being held in Stuttgart over October 4-13.

The German event is a forerunner to the 2020 Tokyo Games, where Biles will be aiming to add to the five medals -- four of them gold -- that she won at the Rio de Janeiro Olympics in 2016.

Even as Biles continues to astonish in competition, she admitted as the national championships began that it was "not easy coming back to the sport, coming back to the organization that has failed you."

She was among more than 200 athletes abused by former US gymnastics team doctor Larry Nassar and has been an outspoken critic of how US Gymnastics and the US Olympic Committee failed to protect athletes.

While she continues to wrestle with the aftermath, Biles's joy was evident on Sunday when she posted a picture of herself on Instagram.

"That feeling when you make history ... twice," the beaming gymnast wrote. (AFP)

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