Jamaica's Melaine Walker starts in her women's 400m hurdles semi-final at the London 2012 Olympic Games at the Olympic Stadium August 6, 2012. REUTERS/Lucy Nicholson (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

Nigeria's Muizat Ajoke Odumosu (L) celebrates next to Ukraine's Hanna Titimets (C) and Jamaica's Melaine Walker after winning the women's 400m hurdles semi-final at the London 2012 Olympic Games at the Olympic Stadium August 6, 2012. REUTERS/Lucy Nicholson (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

Zuzana Hejnova of the Czech Republic (R) clears a hurdle ahead of (L- R) Melaine Walker of Jamaica, Lashinda Demus of the U.S., and T'Erea Brown of the U.S during the women's 400m hurdles event at the Herculis Athletics Meet at Louis II stadium in Monaco July 20, 2012. Hejnova won the race. REUTERS/Eric Gaillard (MONACO - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica blows a kiss to the camera after winning the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Fadi Al-Assaad (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica runs during the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Fadi Al-Assaad (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica (R) runs during the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Fadi Al-Assaad (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica reacts as she crosses the finish-line to win the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Mohammed Dabbous (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica (C) runs during the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Mohammed Dabbous (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica (L) runs during the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Mohammed Dabbous (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica (L) runs during the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Mohammed Dabbous (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica prepares to start the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Fadi Al-Assaad (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica reacts as she crosses the finish-line to win the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Fadi Al-Assaad (QATAR - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica reacts as she crosses the finish-line to win the women's 400m hurdles at the IAAF Diamond League athletics meet in Doha May 11, 2012. REUTERS/Fadi Al-Assaad (QATAR - Tags: SPORT ATHLETICS)

Silver medalist Melaine Walker of Jamaica reacts on the podium after the women's 400 metres hurdles event at the IAAF World Championships in Daegu September 2, 2011. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SPORT ATHLETICS)

Silver medalist Melaine Walker of Jamaica reacts on the podium after the women's 400 metres hurdles event at the IAAF World Championships in Daegu September 2, 2011. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SPORT ATHLETICS)

Gold medalist Lashinda Demus of the U.S. (C) reacts between silver medalist Melaine Walker of Jamaica (L) and bronze medalist Natalya Antyukh of Russia (R) after their women's 400 metres hurdles event at the IAAF World Championships in Daegu September 2, 2011. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SPORT ATHLETICS)

Gold medalist Lashinda Demus of the U.S. (C) stands on the podium between silver medalist Melaine Walker of Jamaica (L) and bronze medalist Natalya Antyukh of Russia (R) after their women's 400 metres hurdles event at the IAAF World Championships in Daegu September 2, 2011. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica celebrates placing second in the women's 400 metres hurdles final at the IAAF World Championships in Daegu September 1, 2011. REUTERS/Phil Noble (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica celebrates placing second in the women's 400 metres hurdles final at the IAAF World Championships in Daegu September 1, 2011. REUTERS/Phil Noble (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica competes in the women's 400 metres hurdles final at the IAAF World Championships in Daegu September 1, 2011. REUTERS/Michael Dalder (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica celebrates placing second in the women's 400 metres hurdles final at the IAAF World Championships in Daegu September 1, 2011. REUTERS/Phil Noble (SOUTH KOREA - Tags: SPORT ATHLETICS IMAGE OF THE DAY TOP PICTURE)

Lashinda Demus of the U.S. leads Melaine Walker (L) and Kaliese Spencer of Jamaica (C) over a hurdle on her way to winning the women's 400 metres hurdles final at the IAAF World Championships in Daegu September 1, 2011. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SPORT ATHLETICS)

(L to R) Melaine Walker of Jamaica, Anastasiya Rabchenyuk of Ukraine and Natalya Antyukh of Russia compete during the women's 400 meters hurdles semifinal second heat at the IAAF World Championships in Daegu, August 30, 2011. REUTERS/Michael Dalder (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica clears a hurdle during her women's 400 metres hurdle semi-final heat at the IAAF 2011 World Championship in Daegu, August 30, 2011. REUTERS/Mark Blinch (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica clears a hurdle next to Natalya Antyukh of Russia (L) and Jasmine Chaney of the U.S. (R) during their women's 400 metres hurdles heat at the IAAF World Championships in Daegu August 29, 2011. REUTERS/Mark Blinch (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica clears a hurdle during her women's 400 metres hurdles heat at the IAAF World Championships in Daegu August 29, 2011. REUTERS/Mark Blinch (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker of Jamaica arrives for a news conference ahead of the IAAF World Championships in Daegu August 25, 2011. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SPORT ATHLETICS)

Melaine Walker (L) and Kaliese Spencer of Jamaica attend a news conference ahead of the IAAF World Championships in Daegu August 25, 2011. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SPORT ATHLETICS)

Jamaica's Prime Minister Bruce Golding (C) stands with gold medallists Shelly Ann Fraser (L), Melaine Walker (R) and Usain Bolt (back) at the Berlin Salute fun day in Trelawny October 4, 2009. The Berlin Salute was organised to honour Jamaican athletes who participated in the 12th IAAF World Championships in Berlin, Germany. REUTERS/Andrew P. Smith (JAMAICA SPORT ATHLETICS)

Melaine Walker, 400 metres hurdles gold medal winner at the IAAF World Championships, looks at Usain Bolt (R) at the Berlin Salute fun day in Trelawny October 4, 2009. The Berlin Salute is to honour Jamaican athletes who participated in the 12th IAAF World Championships in Berlin, Germany. REUTERS/Andrew P. Smith (JAMAICA SPORT ATHLETICS)

Lashinda Demus of the U.S. displays her medal during the awards ceremony for the women's 400 metres hurdles at the world athletics championships at the Olympic stadium in Berlin August 20, 2009. Melaine Walker of Jamaica won the gold, ahead of Demus who won silver and Josanne Lucas of Trinidad and Tobago who won bronze. REUTERS/Wolfgang Rattay (GERMANY)

Lashinda Demus of the U.S., Melaine Walker of Jamaica and Josanne Lucas of Trinidad and Tobago (L-R) display their medals during the awards ceremony for the women's 400 metres hurdles at the world athletics championships at the Olympic stadium in Berlin August 20, 2009. Walker won the gold, ahead of Demus who won silver and Lucas who won bronze. REUTERS/Wolfgang Rattay (GERMANY SPORT ATHLETICS)

Melaine Walker of Jamaica displays her medal during the awards ceremony for the women's 400 metres hurdles at the world athletics championships at the Olympic stadium in Berlin August 20, 2009. Walker won the gold, ahead of Lashinda Demus of the U.S. who won silver and Josanne Lucas of Trinidad and Tobago who won bronze. REUTERS/Wolfgang Rattay (GERMANY)

Melaine Walker of Jamaica poses next to a hurdle as she celebrates winning the women's 400 metres hurdles during the world athletics championships at the Olympic stadium in Berlin August 20, 2009. REUTERS/Max Rossi (GERMANY)

Melaine Walker (R) of Jamaica celebrates with her compatriot Kaliese Spencer after she won in the women's 400 metres hurdles final during the world athletics championships at the Olympic stadium in Berlin, August 20, 2009. REUTERS/Tobias Schwarz (GERMANY)

Melaine Walker of Jamaica celebrates winning the women's 400 metres hurdles during the world athletics championships at the Olympic stadium in Berlin August 20, 2009. REUTERS/Dominic Ebenbichler (GERMANY)

Melaine Walker of Jamaica celebrates winning the women's 400 metres hurdles during the world athletics championships at the Olympic stadium in Berlin August 20, 2009. REUTERS/Dominic Ebenbichler (GERMANY)

Melaine Walker of Jamaica holds up her national flag as she celebrates winning the women's 400 metres hurdles during the world athletics championships at the Olympic stadium in Berlin August 20, 2009. REUTERS/Dominic Ebenbichler (GERMANY)

Melaine Walker of Jamaica holds up her national flag as she celebrates winning the women's 400 metres hurdles during the world athletics championships at the Olympic stadium in Berlin August 20, 2009. REUTERS/Dominic Ebenbichler (GERMANY)

Melaine Walker of Jamaica celebrates after she won in the women's 400 metres hurdles final during the world athletics championships at the Olympic stadium in Berlin, August 20, 2009. REUTERS/Tobias Schwarz (GERMANY)

Melaine Walker of Jamaica poses next to a hurdle as she celebrates winning the women's 400 metres hurdles during the world athletics championships at the Olympic stadium in Berlin August 20, 2009. REUTERS/Dominic Ebenbichler (GERMANY)

Melaine Walker of Jamaica poses next to a hurdle as she celebrates winning the women's 400 metres hurdles during the world athletics championships at the Olympic stadium in Berlin August 20, 2009. REUTERS/Dominic Ebenbichler (GERMANY)

Melaine Walker (C) of Jamaica reacts as her compatriot Kaliese Spencer (L) and Josanne Lucas of Trinidad and Tobago congratulate her with winning in the women's 400 metres hurdles final during the world athletics championships at the Olympic stadium in Berlin, August 20, 2009. REUTERS/Phil Noble (GERMANY)

Melaine Walker (R) of Jamaica reacts next to her compatriot Kaliese Spencer after she won in the women's 400 metres hurdles final during the world athletics championships at the Olympic stadium in Berlin, August 20, 2009. REUTERS/Phil Noble (GERMANY)

Melaine Walker of Jamaica clears a hurdle in the women's 400 metres hurdles third heat during the world athletics championships at the Olympic stadium in Berlin, August 17, 2009. REUTERS/Max Rossi (GERMANY)

Former 100 metres world record holder Asafa Powell of Jamaica answers question from the media at the team hotel in Berlin, August 12, 2009. Powell's participation at the World Athletics championships starting this week will be clarified later on Wednesday, an IAAF official said. Powell and club mates including Olympic champions Shelly-Ann Fraser and Melaine Walker had failed to report for Jamaican national team training in Nuremberg prompting speculation they could be taken off the national team. The IAAF World Championships in Athletics will start on August 15 and run till August 23. REUTERS/Fabrizio Bensch (GERMANY SPORT ATHLETICS HEADSHOT)

Former 100 metres world record holder Asafa Powell of Jamaica leaves a media briefing room at the team hotel in Berlin, August 12, 2009. Powell's participation at the World Athletics championships starting this week will be clarified later on Wednesday, an IAAF official said. Powell and club mates including Olympic champions Shelly-Ann Fraser and Melaine Walker had failed to report for Jamaican national team training in Nuremberg prompting speculation they could be taken off the national team. The IAAF World Championships in Athletics will start on August 15 and run till August 23. REUTERS/Fabrizio Bensch (GERMANY SPORT ATHLETICS)

The accreditation card of former 100 metres world record holder Asafa Powell of Jamaica is pictured as he answers question from the media at the team hotel in Berlin, August 12, 2009. Powell's participation at the World Athletics championships starting this week will be clarified later on Wednesday, an IAAF official said. Powell and club mates including Olympic champions Shelly-Ann Fraser and Melaine Walker had failed to report for Jamaican national team training in Nuremberg prompting speculation they could be taken off the national team. The IAAF World Championships in Athletics will start on August 15 and run till August 23. REUTERS/Fabrizio Bensch (GERMANY SPORT ATHLETICS)

Former 100 metres world record holder Asafa Powell of Jamaica gestures as he answers question from the media at the team hotel in Berlin, August 12, 2009. Powell's participation at the World Athletics championships starting this week will be clarified later on Wednesday, an IAAF official said. Powell and club mates including Olympic champions Shelly-Ann Fraser and Melaine Walker had failed to report for Jamaican national team training in Nuremberg prompting speculation they could be taken off the national team. The IAAF World Championships in Athletics will start on August 15 and run till August 23. REUTERS/Fabrizio Bensch (GERMANY SPORT ATHLETICS)

Former 100 metres world record holder Asafa Powell of Jamaica gestures as he answers question from the media at the team hotel in Berlin, August 12, 2009. Powell's participation at the World Athletics championships starting this week will be clarified later on Wednesday, an IAAF official said. Powell and club mates including Olympic champions Shelly-Ann Fraser and Melaine Walker had failed to report for Jamaican national team training in Nuremberg prompting speculation they could be taken off the national team. The IAAF World Championships in Athletics will start on August 15 and run till August 23. REUTERS/Fabrizio Bensch (GERMANY SPORT ATHLETICS HEADSHOT)

Former 100 metres world record holder Asafa Powell of Jamaica, leaves the team hotel in Berlin, August 12, 2009. Powell's participation at the World Athletics championships starting this week will be clarified later on
Wednesday, an IAAF official said. Powell and club mates including Olympic champions Shelly-Ann Fraser and Melaine Walker had failed to report for Jamaican national team training in Nuremberg prompting speculation they could be taken off the national team. REUTERS/Thomas Peter (GERMANY SPORT ATHLETICS)

Former 100 metres world record holder Asafa Powell of Jamaica, leaves the team hotel in Berlin, August 12, 2009. Powell's participation at the World Athletics championships starting this week will be clarified later on
Wednesday, an IAAF official said. Powell and club mates including Olympic champions Shelly-Ann Fraser and Melaine Walker had failed to report for Jamaican national team training in Nuremberg prompting speculation they could be taken off the national team. REUTERS/Thomas Peter (GERMANY SPORT ATHLETICS IMAGES OF THE DAY)

Lashinda Demus of the U.S. sprints to the finish line during the women's 400m hurdles event at the Herculis athletics meeting at Louis II stadium in Monaco July 28, 2009. Demus is ahead of Sheena Tosta of the U.S. (R) and Melaine Walker of Jamaica. REUTERS/Eric Gaillard (MONACO SPORT ATHLETICS)

Melaine Walker clears the final hurdle to win the Women's 400 meter Hurdles final at the Jamaican Athletics National Championship in Kingston, Jamaica June 27, 2009. REUTERS/Hans Deryk (JAMAICA SPORT ATHLETICS)

Jamaica's Melaine Walker celebrates after winning the women's 400 metres hurdles event at the IAAF World Athletics Final in Stuttgart September 14, 2008. REUTERS/Michaela Rehle (GERMANY)

Jamaica's Melaine Walker celebrates after winning the women's 400 metres hurdles event at the IAAF World Athletics Final in Stuttgart September 14, 2008. REUTERS/Michaela Rehle (GERMANY)

Jamaica's Melaine Walker competes to win the women's 400 metres hurdles event at the IAAF World Athletics Final in Stuttgart September 14, 2008. REUTERS/Michaela Rehle (GERMANY)

Melaine Walker of Jamaica celebrates as she won her women's 400m hurdles race event at the IAAF Super Grand Prix athletics meeting in Lausanne September 2, 2008. REUTERS/Michael Buholzer (SWITZERLAND)

Melaine Walker of Jamaica clears a hurdle to win her women's 400m hurdles race event at the IAAF Super Grand Prix athletics meeting in Lausanne September 2, 2008. REUTERS/Pascal Lauener (SWITZERLAND)

Gold medallist Melaine Walker of Jamaica poses during the medal ceremony for the women's 400m hurdles event of the athletics competition at the Beijing 2008 Olympic Games August 21, 2008. REUTERS/Mike Blake (CHINA)