The world's sports court will decide today on South African runner Caster Semenya's challenge against rules regulating testosterone in female athletes, a verdict expected to have a profound impact on the future of women's sport.

Semenya, a double Olympic champion, is fighting regulations imposed by the International Association of Athletics Federations (IAAF) that compel "hyperandrogenic" athletes - or those with "differences of sexual development" (DSD) - to lower their testosterone levels if they wish to compete as women.