Many people feel they are men and it is unfair to allow them run alongside women because it gives them an unfair advantage.
Although Caster Semanya has undergone genetic testing to prove she is a woman, many people still aren't satisfied.
The deal is: Semanya has a condition called hyperandrogenism (androgen excess), which naturally increases the level of testosterone in the body; a common feature of Polycystic Ovarian Disease (PCOS).
After her win in Berlin 2009, Semenya was considered ineligible to compete as a woman through the IAAF rules on testosterone levels created in 2011.
However, she appealed at the Court of Arbitration for Sports, who slapped a two-year ban on the IAAF rule restricting women with naturally high testosterone levels from competing in sanctioned competitions mid last year.
A fellow runner and competitor, Eunice Sum said: “It is unfair for us to compete against her and it is as well unfair for her to have all these questions since she never created herself like that.”