- By ITV News Video Producer Natalia Jorquera
South African track star Caster Semenya has arrived at court in Switzerland for a case which could alter the future of women's athletics.
The Olympian is challenging a proposal by athletics' governing body to limit testosterone levels in female athletes competing in distances of between 400m and one mile.
- Why is it up to Semenya to challenge the ruling?
Semenya has a condition called hyperandrogenism which means her testosterone levels are naturally elevated.
The average testosterone levels for women are between 0.52 and 2.43 nmol/L (nanomoles per litre of blood), while for men it is between 10.41 to 34.70.
After winning the 800m at the World Championships in 2009 at the age of 18, Semenya was forced to spend 11 months on the sidelines while she underwent sex verification testing.
The results of the tests were never made public, but the 28-year-old was cleared to compete again in women's events in 2010.
Unconfirmed reports suggest that Semenya may have up to three times the testosterone levels of the average woman.
Now, the International Association of Athletics Federation (IAAF) plans to reduce the testosterone limit level from 10 nanomoles per litre to five for female athletes.
The International Olympic Committee is planning to do the same.
If such rules are implemented, Semenya could be barred from competing.
- What does this mean for Semenya?
The IAAF's proposals would require women with elevated testosterone levels to either take medication to reduce their levels, or run against men if they wish to continue competing.
Semenya currently holds the South African record of 1.54.25 for the 800m, not far off the world record of 1.53.28, set in 1983 by Jarmila Kratochvílova of Czechslovakia.
Estimates suggest that if she were to take medication to suppress her testosterone levels, she could end up running between five and seven seconds slower over 800m.
- Is Semenya the only athlete with hyperandrogenism?
Dutee Chand, a sprinter from India was barred by the IAAF from competing against other female runners and was twice dropped from her country's team over hyperandrogenism.
Her 2014 ban was overturned the following year and she has returned to competing.
As a 100m and 200m sprinter, the IAAF's proposed ruling would not affect her.
- When could the new rules come in?
The new IAAF rules were intended to be brought in on November 1, 2018, but were delayed until March 26 after the legal challenge from Semenya and Athletics South Africa (ASA) who are seeking to overturn the ruling.
The case began on Monday at the Court of Arbitration for Sport (CAS) in Lausanne, Switzerland.
- What has Semenya said about the issue?
As she arrived at the court on Monday, Semenya did not take questions, instead only making the peace sign with her fingers.
Semenya’s legal team has argued in papers at the CAS that the IAAF’s regulations are “discriminatory, irrational, unjustifiable, and in violation of the IAAF Constitution”.
The athlete herself has remained tight-lipped on the subject, but frequently posts emotive quotes on her Twitter and Instagram accounts urging people to accept themselves and others for who they are.
- What has the IAAF said?
Arriving at the court on Monday, IAAF President Sebastian Coe said: "The core value for the IAAF is the empowerment of girls and women through athletics.
"The regulations that we are introducing are there to protect the sanctity of fair and open competition."
- What have others said?
The Foundation for Human Rights - a South African organisation - has backed Semenya and criticised the IAAF's proposals as "deeply problematic" and "aimed at excluding certain individuals for no reason other than being what they were born to be”.
They also argue that there a "health risks" associated with making athletes take medication to lower their testosterone levels and the proposal "may indicate a potentially deliberate attempt to focus on attacking outstanding female athletes from developing countries".
South Africa's Sports Minister Tokozile Xasa has backed Semenya.
Nine-times Wimbledon winner Martina Navratilova has also given Semenya her support, hitting out at athletics' governing body for "leaving out sprints and longer distances" from their ruling, something she argued "seems to me to be a clear case of discrimination by targeting Semenya".
- What happens now?
We'll have to wait and see.
A court ruling on the IAAF's proposals is expected before the end of the month, with implications which could change the future of women's athletics.