Micheen was born on 26 June 1987 in Harare, Zimbabwe. She has an older sister and a younger brother. Initially home-schooled for Grade One, Thornycroft went to Springvale House, an independent school in Mashonaland East for primary schooling and on to Peterhouse Girls' School, another independent school also in Mashonaland East, for her secondary education. Peterhouse was the school where she began rowing and met her coach, Rachel Davis. Thornycroft did her tertiary education in South Africa. At Rhodes University in Grahamstown, Eastern Cape, Thornycroft read Human Kinetics and Ergonomics, and Ichthyology and Fisheries studies for her undergraduate education. She then did her Honours in Ichthyology and Fisheries studies. Thornycroft was also president of the Rowing Club and in 2009, she won the Sportswoman of the Year Award at the Rhodes University Sports Council Awards Dinner. Afterward, she went on to do a postgraduate in Teaching at the University of Johannesburg in Johannesburg, Gauteng.
In the buildup to the Olympic Games, Micheen went on to compete in the Paulo D'Alorja regatta held in Italy, she attained sixth place in Final A race. At the World Rowing Cup II, in Lucerne, Switzerland, Thornycroft finished tenth overall. She participated in the 2012 Samsung World Rowing Cup III, held in Munich, Germany and came first in the Final C race and thirteenth overall. At the 2012 Summer Olympics in London, Great Britain, Thornycroft managed to attain fourteenth place overall as she finished second in the Final C race.
2013
In 2013, Thornycroft raced at the World Rowing Cup in Sydney and attained first place in the Final B race. She had training camps in Italy and Germany before participation at the 2013 World Rowing Championships in Chungju, South Korea where she finished fourth in the Final B race. Micheen won gold at the African Rowing Championships in the single sculls in Tunisia.
2014
In April, Thornycroft came out sixth at the Paulo D'Alorja regatta held in Italy. In June, at the World Rowing Cup II in Aiguebelette, France, Micheen finished second in the Final C race. At the 2014 World Rowing Championships held in Amsterdam, Netherlands, Thornycroft achieved a second-place finish in the Final D race and nineteenth overall. She was one of ten Zimbabwean athletes to receive an Olympic Solidarity scholarship to aid preparations for the 2016 Summer Olympics in Rio de Janeiro, Brazil. Micheen came first in the women's single sculls event at the 10th African Rowing Championships held at the Boukerdane Dam in Sidi Amar, Tipaza, a town in northern Algeria.
2015
In a bid to intensify her preparations for the qualifying phase to compete in the 2016 Summer Olympics hosted by Rio de Janeiro in Brazil, she moved to Pretoria, the South African capital, so as to train at the High Performance Centre, at the University of Pretoria, a renowned sport science and training facility. Thornycroft trained under the guidance and coaching of Roger Barrow, South African National Rowing coach credited with coaching the South African M4x crew that won gold at the 2012 London Olympic Games. Under Barrow's tutelage, Thornycroft set her personal best three times. She won gold at the women's single sculls at the SA Rowing Championships and attained Final B race finishes at the World Rowing Cup III in Lucerne, Switzerland and the World Rowing Championships in Aiguebelette, France where she was fifth and sixth respectively. Micheen came first in the women's single sculls event at the 2015 African Continental Qualification Regatta in Tunis, Tunisia and as a result, qualified for the 2016 Olympics.
2016
In February, Thornycroft participated in the women's single sculls event at the Buffalo Regatta in East London, Eastern Cape, South Africa, where she finished first.
Recognition
Micheen Thornycroft was nominated for an ANSA Sportswoman of the Year Award in 2013, with two other nominees, Cara Black and Rachel Goromonzi also being recognised as deserving of the award. The event was held at the Rainbow Towers Hotel in Harare on 11 December. Thornycroft received a silver medal for the accolade whilst Black and Goromonzi received gold and bronze medals respectively. In 2015, Thornycroft was again nominated for an ANSA Sportswoman of the Year Award. The other nominees were Kirsty Coventry and Helen Costa Sinclair. The award show was on 16 December, hosted by the Sports and Recreation Commission at the Rainbow Towers Hotel in Harare. The accolade was given to Helen Costa Sinclair.
Philanthropy
In 2012, Micheen Thornycroft was part of a team of rowers taking part in the rowing edition of the Ubunye Challenge. The 24-hour rowing challenge was an initiative expecting to raise £250,000 to finance educational projects in South Africa and Zimbabwe.
