LONDON — British former marathon runner Paula Radcliffe believes the verdict of a legal case involving Olympic champion Caster Semenya could open the door for transgender athletes to claim an unfair advantage in women's sport.

The Court of Arbitration for Sport (CAS) is expected to rule this month on whether the International Association of Athletics Federations (IAAF) can bring in rules forcing the South African and female athletes with differences of sexual development (DSD) to take testosterone blockers.

Under the new rules, which will apply to women events between 400 meters to the mile, athletes classed as having DSDs must reduce their blood testosterone level to below five (5) nmol/L for a period of six months before they can compete.

Radcliffe said it would be "naive" to think that countries would not actively start cherry-picking girls with hyperandrogenism and forcing them into sport.

"The IAAF has come in for a lot of vilification but there are probably a lot of other sporting federations, particularly where its contact and a physical strength sport, who are really watching this," Radcliffe, the women's marathon world record holder, told Sky news.

"They want to see what it means for the future of female sport and also what it will do in terms of the whole transgender question.

"Will it open the door up there to transgender athletes actually being able to say: 'You know what, we don't need to bring our (testosterone) levels down either, we don't need to have any surgery, we can just identify how we feel and we can come in and compete in women's sport?'

"That would be the death of women's sport."

Since coming out in support for tougher rules on testosterone levels, Radcliffe said she has received abuse on social media.

"A lot of these people that are attacking me wouldn't stand in front of me and say those things to me," Radcliffe added.

"It's very dangerous because there are vulnerable athletes out there who can't make the distinction between what's reality and what's not and what somebody truthfully stands by and someone just being a troll."

Double 800m Olympic champion Semenya has previously denied the claim that she is a threat to women's sport.

China bans Boston Marathon

trio in latest cheating scandal

China has banned for life three runners who broke the rules at the recent Boston Marathon, accusing them of giving the country a bad name and vowing to root out cheats.

Marathon running is growing fast in China but there have been numerous instances of cheating, including a woman who jumped on a bike in a recent domestic race and several others who took shortcuts.

In the latest cases, one entrant at Monday's prestigious Boston Marathon gave his bib to someone else while two other Chinese participants presented forged certificates of previous races to gain entry, the Chinese Athletic Association (CAA) said.

"All the three runners were hit with a life ban from all road running races under the CAA," said Xinhua news agency, citing the association.

"The CAA also reiterated that it will continue to crack down all kinds of cheats in marathons in order to build a healthy and clean environment of road running in China."

The trio's behavior "had a negative impact on China in the (international) community", said the CAA. More than 500 runners from China took part in the 123rd Boston Marathon, Xinhua said.

In 2011 there were just 22 marathons, half-marathons or other running events in China, but that number rocketed to about 1,500 last year. The surge has seen a spike in cheating and at a domestic marathon last month a woman was caught using a bicycle part of the way. China is deploying facial-recognition technology as one way to clamp down. — Agencies