By Sarah Knapton
'Intersex' athletes will learn next month whether they will be forced to take drugs to suppress their testosterone levels, amid an ongoing row which could tarnish the World Championships in London.
South Africa's Caster Semenya, Francine Niyonsaba of Burundi and Kenya's Margaret Wambui could all medal in the 800m final tomorrow, but there have been claims that they are helped to victory by naturally high levels of the male sex hormone.
Semenya, whose testosterone levels are roughly three times that of an average woman, has already been banned once from competing and ordered to take hormone lowering drugs by the The International Association of Athletics Federations (IAAF).
However, the practice of forcing hyperandrogenic athletes to take medication was suspended in 2015 following a challenge from Indian sprinter Dutee Chand. The Court of Arbitration for Sport (CAS) gave the IAAF two years to compile evidence demonstrating that high levels of testosterone had a significant impact on performance.
In the interim, Semenya, Niyonsaba and Wambui have swept the board at international competitions, including the Rio Olympics, leading Britain's Lynsey Sharp to complain that female athletes are effectively competing in 'two separate races'. Semenya won bronze in the 1500m on Tuesday, edging out Britain's Laura Muir by a whisker.
Next month the CAS is expected to rule on new evidence presented by the IAAF showing that high testosterone levels could shave about 2.5 seconds of an athlete's time. There is typically less than two seconds between runners in 800m heats.
However, sports science experts believe the court will refuse to take action for fear of opening themselves up to claims over other naturally occurring advantages, and accusations of sexism.
John Brewer, professor of applied sports science at Queen Mary University in Twickenham, said: "There is a reason that testosterone is a banned substance, it has an anaerobic affect and increases muscle strength and power, so someone with more of it is likely to have more speed. And that's clearly an advantage. It's not a level playing field.
"But what can you do about it? Do you ban them? Do you have a cut-off point? Do you have a separate category? The problem is there will always be athletes who are at the top of a range of physiological values whether it is oxygen uptake, or capillary density, or the ability to tolerate high levels of lactic acid.
"Do you ban all Kenyan athletes because they train at high altitude and so can use oxygen more efficiently? Testosterone levels is just one of many variables that impact performance. And it can work both ways. Someone with more testosterone generally gains more muscle mass and weighs more, so it can be like running with two extra bags of sugar. I think the court will keep things as it is, and this row will keep rumbling on."
Last month scientists from the IAAF published a paper in the British Journal of Sports Medicine concluding that female athletes with high testosterone had a 'significant' competitive edge and called for the advantage to be taken into consideration.
Compared with women with the lowest levels of free testosterone in their blood, those in the top third performed better the 400m sprint (2.73 per cent better), the 400m hurdles (2.78 per cent better); the 800m hurdles (1.78 per cent better); the hammer throw (4.53 per cent better); and the pole vault (2.94 per cent better).
The researchers said increased levels of testosterone could increase mental drive, aggressiveness, and could encourage lean body mass and more efficient oxygen uptake. It may even help pole vaulters and hammer throwers by improving 'visuospatial' awareness, the study concluded.
Stephane Bermon, who led the research from the Monaco Institute of Sports Medicine and Surgery, said: "This study brings new evidence of the performance-enhancing effects of androgens in elite female athletes. Although long suspected to be the case, until now there was no proof."