Doctors and athletes are debating new restrictions on South African runner Caster Semenya's testosterone levels

South African middle-distance runner Caster Semenya, who has two Olympic gold medals in the 800-meter competition, received news on Wednesday that could severely alter the course of her illustrious career — and it's already stirred quite a debate in the sports world.

Semenya had appealed a new rule instituted by the International Association of Athletics Federation which would force female runners like Semenya, who have naturally elevated levels of testosterone, to take testosterone blockers to compete in races from 400 meters to a mile. But the Court of Arbitration for Sport denied the appeal, which means the 28-year-old Semenya will either have to take the medication or stop competing altogether. Either way, the ruling is surely a blow to one of the sport's most gifted athletes just one year before the next Olympics.

Some observers, including famed American sprinter Michael Johnson, said that while it was no fault of Semenya's, the court's ruling was the only way to ensure fair competition.

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Semenya has plenty of supporters, however, especially in her home country of South Africa. Several analysts have also pointed out that biology creates advantages for athletes in nearly every sport. USA Today's Nancy Armour, for example, asks what the reaction would be if legendary U.S. swimmer Michael Phelps was banned from competing because of his preternaturally long wingspan.

Others say the IAAF's decision could have other consequences beyond athletic records: One doctor says it could ultimately be a choice between competing and caring for her mental health. Tim O'Donnell