If Simone Biles is to become the first female gymnast to win five gold medals in one Olympics, she'll need to do something she's never been done before: win the title of best vaulter in the world. At the last three world championships, Biles has won multiple gold medals in the all-around, team competition, balance beam and floor finals. But she's only ("only" is very relative here) managed two silvers and a bronze on vault.
All three times, Biles shared the vaulting podium with North Korea's Hong Un-Jong. In previous years, both Hong and Biles competed the same Amanar vault, which is two-and-half-twists off the vaulting table. But Hong had the advantage over Biles because her second vault was a Cheng, a vault with a half twist onto the vaulting table and one-and-a-half twists off, which was worth more difficulty points than Biles' second vault. In 2016, Biles upgraded to the Cheng so she would be on an even playing field with the other top vaulters in the world.
Hong may have regained her edge in a big way, though. In a training video from Rio, Hong is shown doing a triple-twisting Yurchenko, which is the Amanar plus an extra half twist. The tripe-twisting Yurchenko has never been done in competition before by a female gymnast.
27-year-old Hong won gold on vault at the 2008 Beijing Olympics, winning North Korea's first Olympic medal in women's gymnastics. But Hong had to sit out the London Games after all North Korean gymnasts were banned for falsifying the ages of one of their athletes. That athlete happened to be Hong Su-Jong, Hong's sister, or possibly her twin. The two have the same birthdate, but Hong Su-Jong competed under multiple birth years, one of which would have made her ineligible to compete at the 2004 Athens Olympics.
If a gymnast wants to compete a new gymnastics skill, they must submit it to the International Gymnastics Federation (FIG) before the competition so it can be rated and assigned a difficulty value. Hong has submitted the triple-twisting Yurchenko at the 2013, 2014 and 2015 World Championships, but never done it in competition. If she completes it at the Rio Olympics, it will be named after her and become known as the Hong vault. It would be worth 6.8 difficulty points, half a point ahead of the Amanar—and could launch her to a gold medal.