Kenya's Olympic 800 metres bronze medallist Margaret Nyairera Wambui can feel her career slipping away from her, with no idea when, or if, she will be able to compete internationally again.

The 24-year-old is one of several star female athletes affected by an International Association of Athletics Federations (IAAF) ruling this month that requires women with high levels of testosterone to take medication to suppress it.

Seated at a dirt-track stadium at the foot of the Ngong Hills outside Nairobi where she trains, Wambui has just returned from a disappointing sixth-place finish in the 800m at the Doha Diamond League.

She was meant to leave for the IAAF World Challenge athletics meeting in Nanjing next week, but now her future is one big question mark.

“I am very disappointed, I don't feel even like going on with the training because you don't know what you are training for,” she told AFP.

The new IAAF rules took effect on May 8 after South Africa's two-time Olympic 800m champion Caster Semenya lost a legal challenge against them.

The IAAF has maintained that the rules are necessary for fair competition, arguing that athletes with high levels of testosterone benefit from increased bone and muscle strength similar to men who have gone through puberty.

However, critics highlight that the very nature of elite athletic success is down to one physical advantage or another, such as swimmers with disproportionately big hands or feet, or basketball players who are taller than the average person.

“Why, when you have a high level of testosterone in men, you are likely to perform well and we celebrate that? But when it comes to women we have to tell them to lower it and we draw them out of competition. Why?” asked Wambui.

“Why don't we take maybe men with low testosterone and categorise them as women?”

The new rule applies to distances from 400m to a mile, and includes the heptathlon, which concludes with an 800m race.

Wambui said simply switching to another distance like 5,000m was not possible, with different skills and training needed that would take years to reach elite level.

“I am not going to take medication because I am not sick and … those are chemicals you are putting in your body, you don't know how it will affect you later,” she said.

She said that maybe the idea of having different categories of runners — comparing it to boxing, where heavyweights don't fight flyweights — might be “a good idea to make it fair.”