South African athlete Caster Semenya says she has a target on her back because she is the best at what she does. Speaking on the sidelines of a Top Women Conference in Johannesburg, she says people don't question differences in men who compete against each other, but they do in women. Semenya is banned from defending her world 800m title in Doha in September by a Swiss court ruling which revoked a temporary suspension on the IAAF's controversial testosterone-curbing rules.