At the
2006 Commonwealth Games in
Melbourne, Koudinov was New Zealand's youngest representative at the age of 14. He placed eighth with New Zealand in the team competition, and he finished 20th in the all-around final. He competed in his first
World Championships in
2007 in Stuttgart, Germany. At the
2009 World Championships, Koudinov placed 59th in the all-around qualifications. He moved to the United States in 2010 to compete for the
Ohio State Buckeyes gymnastics team. He finished sixth in the individual all-around final. Koudinov finished eighth in the all-around at the
2014 Commonwealth Games. He then finished 50th in the all-around qualifications at the
2014 World Championships. Then at the
2015 World Championships, he finished 48th in the all-around qualifications and advanced to the
2016 Olympic Test Event. Koudinov was one of three New Zealand gymnasts who competed in the
2016 Summer Olympics in Rio; the other two were
Courtney McGregor and
Dylan Schmidt. Collectively, they became New Zealand's first Olympic gymnasts since 2000. He placed 45th in the all-around
qualifications and did not advance into any finals. Koudinov planned on retiring after the
2017 World Championships and moved back to New Zealand, but the national team head coach convinced him to continue for the
2018 Commonwealth Games. Koudinov won the all-around title at the 2021 Oceania Championships and also won the continental berth for the
2020 Summer Olympics. In 2022, Koudinov was selected to compete at his fifth Commonwealth Games. However, he had to withdraw from the all-around final due to an injury. Koudinov won the all-around title at the 2023 Oceania Championships and advanced to the
2023 World Championships. He was not able to compete at the 2024 Oceania Championships due to an injury and therefore could not qualify for the
2024 Summer Olympics. == Eponymous skill ==