[3] On 10 August 1965, aged twelve years, Muir became the youngest person to break a sporting world record in any discipline when she swam the 110 yards backstroke in 1m 08.7s at the ASA National Junior Championships in Blackpool, England.

[8] Due to the sporting boycott of South Africa during her active career, she was never able to participate in an Olympic Games.

After retiring from her sport, she qualified, through the University of the Orange Free State,[3] as a doctor and practiced in the African continent.

[10] Muir died of breast cancer at the age of 60 in Mossel Bay, South Africa on 1 April 2013.

[3] When Muir revisited the city in 2009 she donated her Springbok blazer to the Diamantveld High School.