The following year she won the vault final at the World Championships. She performed the two most difficult vaults in the final.[3] In 2015 Hong again represented North Korea at the World Championships held in Glasgow. Though she retained her full difficulties and performed impressively, she failed to defend her title and won a silver medal instead. She was behind Russia's Maria Paseka by 0.033 point. At the 2016 Summer Olympics, she qualified second into vault finals behind Simone Biles. In the finals she performed a solid Cheng to start. For her second vault, she became the first female gymnast to ever attempt a triple twisting yurchenko vault; however she under rotated and sat down the vault, getting the vault devalued to an Amanar, and ultimately missed the podium.
Hong Un-jong is the sister of Hong Su-jong, with whom she shares a 9 March birthday. Hong Su-jong had three different birth dates listed for her (1985, 1986, or 1989) at various competitions.[4] At the 2004 Summer Olympics, she competed under the 1985 birth date, but the 1989 birth date would have meant that she was too young to compete.[5] In November 2010 Hong Su-jong was permanently banned from all international competition as a consequence of providing inconsistent age information. North Korea was also banned from all international competition until October 2012 due to this incident, which most significantly included the 2012 Summer Olympics.[6] Hong Un-jong has never been personally implicated in the age falsification, but the consequent country-wide ban meant that she could not defend her Olympic title on vault.
In a video, Hong Un-jong appeared to admit that Hong Su-jong is her twin.[7] If accurate, this would mean that Hong Su-jong was in fact born in 1989, confirming the age falsification.
North Korea
