– literally "racing cycle" – is a form of motor-paced cycle racing in which track cyclists sprint for victory following a speed-controlled start behind a motorized or non-motorized pacer. It was developed in Japan around 1948 for gambling purposes and became an official event at the 2000 Olympics in Sydney, Australia. Riders use brakeless fixed-gear bicycles. Races are typically long: 6 laps on a track, 4 laps on a track, or 4 laps on a track. Lots are drawn to determine starting positions for the sprint riders behind the pacer, which is usually a motorcycle, but can be a derny, electric bicycle or tandem bicycle. Riders must remain behind the pacer for 3 laps on a track. The pacer starts at , gradually increasing to by its final circuit. The pacer leaves the track before the end of the race (3 laps on a track). The winner's finishing speed can exceed . Competition keirin races are conducted over several rounds with one final. Some eliminated cyclists can try again in the repechages. World championships Keirin, in its modified form, has been a UCI men's World Championship event since 1980 and a UCI women's World Championship event since 2002. Danny Clark of Australia and Li Na of China were the first UCI world champions. The 2019 men's and women's world champions are Matthijs Büchli of Netherlands and Lee Wai Sze of Hong Kong. Olympics Keirin made its debut at the 2000 Summer Olympics in Sydney as a men's event, after being admitted into the Olympics in December 1996. The women's event was added for the 2012 Summer Olympics in London. A BBC News investigation, reported in July 2008, found evidence that following admission into the Olympics, the Union Cycliste Internationale required (in writing) the Japan Keirin Association to support UCI projects in "material terms"; over a period of time the association subsequently gave US$3 million to UCI in consideration of "the excellent relationship the UCI has with representatives of the Olympic movement". The UCI and its then-president, Hein Verbruggen, denied any wrongdoing. At the Tokyo 2020 Olympics, the Men's keirin took place on 7 and 8 August 2021, with 30 cyclists from 18 nations competing, and the gold medal going to Jason Kenny from Great Britain. The Women's keirin took place on 4 and 5 August 2021, with 29 cyclists from 18 nations competing, and the gold medal going to Shanne