Unfortunately this was handled appallingly by the South African authorities and the innocent Semenya painted as the villain of the piece. After this debacle, the IAAF gathered a large, multidisciplinary group of experts to examine the problem of how best to determine eligibility for women's sport. After meetings in Lausanne and Miami, the group issued a consensus decision in 2011 to introduce an upper limit for testosterone levels of 10 nmol/L. This was subsequently endorsed by the IOC in 2012. This level is well above levels normally found in female athletes (99% have levels below 3 nmol/L) and ensures that the only athletes recording higher levels are transgender athletes (or are doping!). As a result, intersex athletes such as Semenya had the choice of taking medications, or having surgery to remove the organ producing the excess testosterone, in order to reduce testosterone levels to under the limit. After Berlin, Semenya got silver medals in the London Olympics in 2010 and the 2011 World Championships. However in the last couple of years since the introduction of the IAAF rules, she has struggled to perform at anywhere near world class level, failing to even qualify for the 2014 Commonwealth Games or advance beyond the semi-finals in last year's World Championships in Beijing. This season though Semenya has already produced some remarkable performances. A month ago, she won the 400m, 800m and 1500m at the South African championships, all on the same day. The 400m and 800m, 50 minutes apart, were run in 50.7s and 1:58. Since then Semenya has won two Diamond League meets in times of 1:56.46 and 1.56.64 seemingly with ease.

It is likely that if she pushed herself harder, Semenya could break the World 800 metre record of 1.53.28. This is the longest standing record in womens athletics and was set in 1983 by the Czech athlete Jarmila Kratochvilova who at the age of 32 was running the event for the first time. The record was set at a time when doping in womens' athletics was rife and is generally regarded as having been pharmacologically assisted (though vehemently denied by the athlete herself). There is an obvious reason for Semanya's dramatic return this season to the sort of form she showed as an 18 year old. In July last year the Court of Arbitration for Sport (CAS) threw out the IAAF's ruling on an upper limit of testosterone as a result of a case brought by the Indian athlete Dutee Chand who had been outed in her country as an intersex athlete. The CAS ruled this way because they felt that there was insufficient evidence for the performance benefits of elevated testosterone level, a decision described by Tucker as "one of the stupidest, most bemusing legal/scientific decisions ever made". The IAAF has two years from the time of the ruling to make a better case for the HA regulations or CAS will abolish them. So now athletes such as Semenya no longer have to artificially reduce their testosterone levels. As a result Semenya has gone from someone struggling to run 2.01 in the last couple of seasons to her current status as hot favorite for the gold medal in Rio and likely to beak the longstanding world record. In the same blog mentioned above, Ross Tucker interviewed Joanna Harper who describes herself as a "scientist first, an athlete second, and a transgender person third" and as such is the only transgender person in history to be part of the team to advise the International Olympic Committee (IOC) on gender-based issues.

Harper fears that "much of the anticipation for the upcoming Rio Olympics will be overshadowed by the spectre of intersex athletes dominating some events in women's athletics, the premier sport of the games. It is also unfortunate that many people will blame the medal-winning intersex athletes whose only crime is to compete with the gifts that nature gave them. The real problem is that sports need some policy governing intersex athletes and currently there is none". She also points out that Semenya will not be the only intersex athlete likely to medal at the Games. Harper suggests that in the 800 metre event alone, we could see an all intersex podium with five of the eight finalists being intersex athletes. There is no doubt that this is an extremely complex and emotional issue involving human rights issues, medical definitions of transgender, and sporting ethics. There is no perfect solution to the problem and as a result of the CAS ruling, the issue of transgender and intersex athletes will dominate the headlines in Rio. Let's leave the last word to the scientist, athlete, transgender Joana Harper. "I believe that billions of potential female athletes deserve the right to compete with some semblance of a level playing field, and that requiring all women to compete within a given testosterone range is the best way we currently have to create such a playing field". Sadly that will not be the case in Rio.

Peter Brukner is Professor of Sports Medicine at La Trobe University. Ross Tucker's blogs can be found at sportsscientists.com