She began her career with the Calgary Aquabelles club in 1965 and won silver medals in the synchronized swimming team competitions at both the 1971 Pan American Games and the 1973 World Aquatics Championships.

[1] She competed in the 1971 Pan American Games in Colombia,[3][7] claiming the silver medal in the synchronized swimming team competition as a member of Canada's seven-athlete squad for the event.

[4] The following year, she coached Helen Vanderburg and Michelle Calkins to victory over the United States and Japan at the 1977 Pan Pacific Championships.

[3][11] Muir's first international victory as a coach came at the 1978 World Aquatics Championships in Berlin when Vanderberg claimed the gold medal in the solo competition and Vanderburg and Calkins paired up to win the duet discipline.

In 1979, swimmers coached by Muir won medals at that year's FINA Cup in the solo and duet events and at the Pan-American Games.

Her athletes achieved two gold medals in the duet and solo competitions at each of that year's Commonwealth Games and the World Aquatics Championships in Madrid.

[1] In the same year, Muir wrote a letter to Synchro Canada expressing concern that synchronized swimming would be excluded from the Olympic program.

[1][2] At the 1992 Summer Olympics in Barcelona, she helped to employ her underwater synchro abilities to enable Mark Tewksbury's gold medal win in the 100 meter backstroke.

Muir is a member on the board of directors of the Canadian Centre for Ethics in Sport and is a graduate of the Royal Roads University's Executive Coaching program.