According to his Olympic profile, Yang started his gymnastics career at the age of 9, following his brother's footsteps. Yang is currently attending the Korea National Sport University. Yang's parents are Yang Gwan-gwon and Ki Suk-hyang. Their impoverished family previously lived in one of Gwangju's shantytowns, before relocating to North Jeolla Province's Gochang, in South Korea's countryside, in 2010, after his father, a construction worker, suffered from serious injuries. His family currently lives in a makeshift converted greenhouse constructed from PVC pipes. After Yang's father lost his job, Yang supported the family with a modest income from the Korea Gymnastic Association. Yang's coach Cho Sung-doe admitted that he had been unaware of the family's precarious financial situation before Yang won the gold medal.
Career
Yang placed fourth and just missed medaling in the individual vault final at the 2010 World Championships in Rotterdam, and would later become vault champion at the 2010 Asian Games and then 2011 World Artistic Gymnastics Championships in Tokyo, Japan. In 2012, he became the first Korean gymnast to win Olympic gold in gymnastics, winning the vault competition in London. In 2013, he went on to win gold in vault at the 2013 Summer Universiade in Kazan, Russia. He is famous in the gymnastics world for performing one of the five hardest vaults in the world, the Yang Hak Seon, which is a front handspring on and into three twists off in a layout position. It was unveiled at the in the individual vault final at the 2011 World Championships, and initially carried the highest ever difficulty score of 7.4 in men's vault at the time under the 2009-2012 Code of Points. The difficulty value of the Yang Hak Seon has been adjusted at the beginning of subsequent quads since, initially down to 6.4 under the 2012-2016 CoP and now further to 6.0 under the current 2017-2020 CoP. The International Gymnastics Federation regularly reassesses and adjusts D-scores due to the steady advancement of general skill levels over time in gymnastics, especially on vault because of its D-scores being assigned numeric values instead of alphabetical representations like with the other apparatuses—vault is the only apparatus in gymnastics to have that simply due to the nature of the apparatus. Yang is additionally said to be working on a second difficult vault, but this one is a sideways entry. Yang was a reigning world champion, having won gold in vault at both the 2011 and 2013 World Championships in Tokyo and Antwerp respectively. However, at the 2014 World Championships in Nanning, China, he fell on both of his vaults—the first for which it was announced in Nanning that he has received naming credit for a brand new top then 6.4 difficulty vault, now officially named the Yang Hak Seon 2, or a straight Tsukahara with 3½ twist—failing to defend his title and finished in seventh place with a final average combined score of 14.416 after qualifying in first place. Without any worthy competition, Ri Se Gwang of North Korea won the gold medal with two top then 6.4 difficulty vaults that were both named after him, the Ri Se Gwang and Ri Se Gwang 2, and outscored Yang by exactly one full point. He was similarly unable to defend his Olympic title at the 2016 Summer Olympics in Rio de Janeiro due to injury. At the 2017 Artistic Gymnastics World Championships in Montreal, Canada, Yang had "qualified" in first place for the vault event final but pulled out after that because he had sustained a hamstring injury during qualifications. Unimpeded and with little resistance, Kenzo Shirai of Japan won his world individual vault title with an averaged combined score of 14.900 ahead of vault's 2012 Olympic bronze medalist Ihor Radivilov of Ukraine by 0.001, the absolute slimmest of margins. At the 2019 World Artistic Gymnastics Championships in Stuttgart, Germany, Yang had qualified for the individual vault event final in first place, but finished eighth after falling out of the first vault—his own the Yang Hak Seon on vault, or front handspring triple twist—as well as incurring a 0.300 penalty for stepping out-of-bounds because of that.
The difficulty above is in line with the 2017–2020 Code of Points. Yang currently shares the honour with only Kenzō Shirai of Japan and Ri Se Gwang of North Korea for having at least one of the five skills with the highest D-score of 6.0 in men's vault under the FIG's most current 2017–2020 Code of Points to be named after them. The Yang Hak Seon is a front handspring entry family vault, and it has a front handspring take off entry onto the vaulting platform and then into a triple-twisting layout off the platform to finish in a blind landing. The Yang Hak Seon 2 is now a straight forward-entry Tsukahara with 3½ twist, or Kasamatsu with 2½ twist. Currently, Yang has two, Ri has two, and Shirai has one. Even though some may refer to the Yang Hak Seon vaults by just using Yang's surname, it is not quite accurate. This is because Yang's surname, like in Korean and Chinese names, is not customarily listed at the end; hence, Yang's entire name in customary order must officially be used in the naming of any skill he has originated. Although a gymnast may have officially received naming credit for a skill, it is becoming more common for that name not to necessarily be used in practice. This is in light of the ever increasing number of eponymous skills across all events for MAG as well as identical corresponding skils for WAG, which would receive an official second name as well. Moreover, using eponymous names is getting more confusing outside of experts in the field. Therefore, technical abbreviations are also extensively used over official names when describing certain skills for them to be more readily understood by everyone. For example, the Yang Hak Seon 2 is more widely just called "Tsukahara 3½" as the latter is easier to identify by more people. Also, the "2½-twisting Yurchenko" has two official names: the Shewfelt for MAG and Amanar for WAG. The latter is more popular in practice, and confusion has occurred depending on which situation the skill is being described.
