Doug Turnbull started training in Kyokushin in 1971 under the then Sensei John Taylor (now 8th dan) . While part of the Australian Kyokushin Karate Association (AKKA), which was affiliated with the IKO in Japan, he attained shodan in 1975, nidan in 1980, sandan in 1985, yondan in 1990. In 1995, after Mas Oyama's passing and because of the political turmoil in Japanese Kyokushin, he joined Hanshi Steve Arneil's UK based International Federation of Karate, and shortly after took over the role as the chairman of the Australian branch, the International Federation of Karate Kyokushinkai Australia Inc. (IFKKA). In 1996 he was awarded godan by Hanshi Arneil, and in 2006 Hanshi Arneil promoted him to rokudan.

He participated in almost all major Australian Kyokushin tournaments as a judge and/or referee between 1981 and 1995, and in all the national training camps between and including 1983-1993.

In 1997, after joining the IFK, he was a referee at the finals of the 1st IFK World Championships in Moscow, and in 2005 he also refereed at the 3rd IFK World Championships in London.

He has been teaching karate since 1976, and founded his own dojo in Marrickville in 1982 at which he still teaches, though in 2005 it moved location to Tempe Public School.

He attained an International Referee's certificate, which is for full-contact kumite, is accredited for non-contact kumite, including mirror judging, Kyokushin kata judging, and, while the Federation of Australian Karatedo Organisations (FAKO) still existed, had a "C" level FAKO accreditation as a judge. (The organisation has since been restructured and renamed as the AKF (Australian Karate Federation).

In 1999 and 2000 he was voted the Best and Fairest Official for NAS NSW, and in 2005 he was accredited as a Level 4 referee with the National All Styles (NAS) .

His competition experience includes a first place in the NSW kumite championship, and two kata first place titles (one at State and the other at National level).

On the administrative side, he was on the judging panel for the AKKA State Senior Gradings during 1994 and 1995, and a Tournament Organising Committee member since 1983 until he left.. He was Editor-in-Chief of "SHIN", the national Kyokushin magazine, from 1983 to 1987. He was also Junior Vice Chairman for the New South Wales AKKA from 1990 until it split up in 1994, and is currently Chairman and Chief Referee of the IFKKA. in 2005 he was appointed to both the position of National All Styles national referee trainer and NSW NAS Technical Director.

He has also had the good fortune of training at Honbu dojo in Japan.