Tennis great Martina Navratilova has come to the defence of Olympic 800 metres champion Caster Semenya ahead of next week's landmark hearing on proposed rules that aim to restrict testosterone levels in female athletes. The International Association of Athletics Federations (IAAF) has proposed rules that would force so-called "hyperandrogenic" athletes or those with "differences of sexual development" (DSD) to medically lower their testosterone levels below a prescribed amount.

Track and field's global governing body wants to introduce the rule changes in order to promote what it says will be fairer competition between all female athletes. But South Africa middle-distance star Semenya, the most high-profile athlete who would be affected by such an alteration to the rule book, is challenging the legality of the IAAF's proposals in a case which will be heard at the Court of Arbitration (CAS) in Lausanne from Monday.