Career
His last appearance as a speed skater was at the 1980 Winter Olympics in Lake Placid, where he placed 5th in the 1,000 m, 1.93 seconds behind the winning time of Eric Heiden. After ending his speed skating career, Mueller became a very successful skating coach. In addition, several speed skaters winning a total of five World Sprint Championships, one World Allround Championships, and one European Allround Championships titles were also coached by him.
Since the 2003/2004 season, Mueller was the coach of the Norwegian team
He quickly added to his list of successes as a coach when, at the World Single Distance Championships of 2005 in Inzell, Even Wetten (on the 1,000 m) and Rune Stordal (on the 1500 m) became World Champions. Mueller was fired as coach of the Norwegian team in November 2009, due to allegations of harassment of skater Maren Haugli.
He and Timmer are now divorced. An autobiography, called Op dun ijs ("On thin ice"), was published in the Netherlands in 2006.