When Biles debuted this skill, other elite gymnasts had mastered a double layout with a full twist, but she was the first to do so on the world stage with just a half twist. That half twist leads to what is known as a “blind landing” because the gymnast cannot see the ground as her feet are approaching the floor.

In most cases, the more a gymnast twists, the harder the element is. However, with this skill, the half twist makes the landing more difficult. Still, in the Code of Points — in which skills are given a letter value based on their complexity, with A being the easiest — the full-twisting double layout is rated an H, while the Biles I is considered slightly easier as a G.

All of Biles’s named skills are complicated, but compared with the others, this is the easiest of the five. Sometimes she performs a jump immediately after she lands to increase her overall difficulty score.

Some of the world’s top vaulters perform a Cheng, named for Chinese gymnast Cheng Fei. That vault is the same as the Biles I but includes a 1½ twist rather than a double twist. By adding an extra half twist, Biles raised the difficulty. The Biles I has a difficulty score of 6.0 — four-tenths higher than the Cheng (5.6).

Biles performed this skill just a few times in 2018. Since then, she has opted for the Cheng or other vaults.

Many top gymnasts perform a double-flipping dismount in a tuck or pike position without twisting. A full-twisting double tuck off the beam is an extremely difficult dismount that just a few gymnasts perform. Before Biles debuted this element, a double-twisting double tuck beam dismount was nearly unthinkable. The height and power required to execute this skill safely is difficult to generate.

Biles unveiled this dismount in 2019, and she performed it again at the U.S. Olympic trials in 2021. Over the past two years, Biles has dismounted with a full-twisting double tuck instead. Her coach Cecile Landi said in 2023 that it wasn’t worth it for Biles to perform the double-double because she probably would incur more deductions on the landing than the only slightly higher difficulty score would be worth.

The women’s technical committee of the International Gymnastics Federation (FIG) determined Biles’s double-double dismount should be awarded an H difficulty rating. No other skill on beam has a higher value, but the rating is just one tier above the full-twisting double tuck dismount, which is a G. That means the extra twist leads to just a 0.1-point increase in Biles’s score.

After the FIG released the value for the skill, Biles responded to the decision in a tweet with a long series of “hahaha” followed by “bull----.” At the time, USA Gymnastics said in a statement that it “respectfully disagrees” with the value assigned.

The women’s technical committee said in a statement that it considers the safety of gymnasts when assigning values, noting there is increased risk in double-flipping beam dismounts, “including a potential landing on the neck.” The committee essentially decided to give this dismount a lower value in an effort to dissuade gymnasts from attempting it, rather than assigning it a value that matched its true difficulty.

From the time Biles debuted this skill in August 2019 until the Tokyo Olympics in 2021, she included the element in every floor routine she performed. However, when Biles returned in 2023 after a break from the sport, this difficult tumbling pass was no longer part of her competitive repertoire. The skill, often referred to as a triple-double, returned to her routine in 2024 ahead of the Paris Games.

The third twist significantly increases the difficulty of this skill. Completing two twists during one of the flips requires a gymnast to twist very quickly. American Jade Carey, the floor champion in Tokyo, practiced a triple-twisting double layout — which is more difficult than the tuck version — during a training session before a 2021 competition. The triple-twisting double layout would bear Carey’s name if she had performed it at a major event, but she never did. And when asked about the skill in 2023, Carey said: “I think that ship has sailed. I’m a little bit scared now.”

This skill is also known as a Yurchenko double pike. The term “Yurchenko” refers to the entry onto the vault and is named for Natalia Yurchenko, a world champion for the Soviet Union; it’s the most common type of vault at the elite level. Biles became the first woman to perform a Yurchenko-style vault with two flips in the air.

All other female elite gymnasts have performed Yurchenko vaults with just one flip. They opt to add twists to increase difficulty. (Some gymnasts, including Biles, have mastered 2½-twisting Yurchenkos, but the triple-twisting Yurchenko has yet to be successfully performed in women’s gymnastics.) The second flip in the Yurchenko double pike makes it extraordinarily difficult.

“The double pike, it’s never been normal, and it never will be,” said Joscelyn Roberson, an alternate for the U.S. Olympic team who trains alongside Biles.

Biles stunned the gymnastics community when she posted a video of herself practicing this skill in February 2020; before then, a double-flipping Yurchenko was not perceived to be a realistic element in women’s gymnastics. Biles has said she initially practiced this skill as a way to work on her push off the table to improve her other Yurchenko-style vault.

Eventually, Biles realized she could safely perform the Yurchenko double pike in a competition, and she unveiled the vault at the U.S. Classic in May 2021. She didn’t perform the skill again that season, including at the Olympics, where she withdrew from multiple events, including the vault final. But Biles did the Yurchenko double pike at about half of her competitions in 2023, and at the world championships, the skill officially became known as the Biles II.

“People, I hope, realize that maybe that’s one of the last times you’re going to see a vault like that in your life from a women’s gymnast,” Coach Laurent Landi said after Biles performed this vault at the world championships last year. “I think it’s time to appreciate that.”

Biles has performed the Yurchenko double pike at every competition in 2024, and it could propel her to a gold medal in Paris. This vault has a difficulty value of 6.4, which is higher than every other vault in women’s gymnastics.