Nancy Jebet Langat of Kenya, Siham Hilali of Morocco, Faith Chepngetich Kipyegon of Kenya, Genzebe Dibaba of Ethiopia, Zoe Buckman of Australia and Elena Korobkina of Russia (L-R) race in the women's 1500 metres semi-final heat event of the IAAF World Athletics Championships at the Luzhniki Stadium in Moscow, August 13, 2013. REUTERS/Lucy Nicholson (RUSSIA - Tags: SPORT ATHLETICS)

Kenya's Nancy Jebet Langat (L), New Zealand's Nikki Hamblin (C) and Scotland's Stephanie Twell cross the finish line in the women's 1500-metre final at the Jawaharlal Nehru Stadium during the Commonwealth Games in New Delhi October 8, 2010. REUTERS/Suzanne Plunkett (INDIA - Tags: SPORT ATHLETICS) 

Kenya's Nancy Jebet Langat crosses the finish line in the women's 1500-metre final at the Jawaharlal Nehru Stadium during the Commonwealth Games in New Delhi October 8, 2010. REUTERS/Suzanne Plunkett (INDIA - Tags: SPORT ATHLETICS) 

Kenya's Nancy Jebet Langat (L) celebrates after crossing the finish line ahead of England's Hannah England (R) in the women's 1500-metre final at the Jawaharlal Nehru Stadium during the Commonwealth Games in New Delhi October 8, 2010. REUTERS/Suzanne Plunkett (INDIA - Tags: SPORT ATHLETICS) 

Nancy Jebet Langat of Kenya signs autographs after winning the women's 1500 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Arnd Wiegmann (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Nancy Jebet Langat of Kenya celebrates after winning the women's 1500 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Arnd Wiegmann (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Nancy Jebet Langat of Kenya signs autographs after winning the women's 1500 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Arnd Wiegmann (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Nancy Jebet Langat (R) of Kenya crosses the finish line to win the women's 1500 metres event at the IAAF Diamond League athletics meeting at the Letzigrund stadium in Zurich August 19, 2010. REUTERS/Ruben Sprich (SWITZERLAND - Tags: SPORT SPORT ATHLETICS)

Ethiopia's Gelete Burka (C) runs to win the women's 1500 metres competition at the IAAF Diamond League athletics meeting at the Stade de la Pontaise in Lausanne July 8, 2010. The picture shows from LtoR: Kenya's Nancy Jebet Langat, Gelete Burka and Ibtissam Lakhouad of Morocco. REUTERS/Michael Buholzer (SWITZERLAND - Tags: SPORT ATHLETICS IMAGES OF THE DAY) 

Nancy Jebet Langat of Kenya pulls ahead to win the women's 1500m during the IAAF Diamond League Grand Prix track and field meet in New York June 12, 2010. REUTERS/Keith Bedford (UNITED STATES - Tags: SPORT ATHLETICS) 

Nancy Jebet Langat of Kenya crosses the finish line to win the women's 1500m final of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 23, 2008. REUTERS/Kim Kyung-Hoon (CHINA)

Gold medallist Nancy Jebet Langat of Kenya poses during the medal ceremony for the women's 1500m final of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 23, 2008. REUTERS/Mike Blake (CHINA)

Maryam Yusuf Jamal of Bahrain (front) looks back at Nancy Jebet Langat of Kenya during the women's 1500m final of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 23, 2008. REUTERS/Dylan Martinez (CHINA)

Nancy Jebet Langat of Kenya reacts after winning the women's 1500m final of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 23, 2008. Lisa Dobriskey (rear) of Britain finished fourth. REUTERS/David Gray (CHINA)

Nancy Jebet Langat of Kenya walks on the track after winning the women's 1500m final of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 23, 2008. Lisa Dobriskey (rear) of Britain finished fourth. REUTERS/Dylan Martinez (CHINA)

Nancy Jebet Langat of Kenya gestures as she crosses the finish line to win the women's 1500m final of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 23, 2008. Iryna Lishchynska of Ukraine (back R) finished second and her compatriot Nataliya Tobias (back L) third in the event. REUTERS/Dylan Martinez (CHINA) 

Nancy Jebet Langat of Kenya gestures as she crosses the finish line to win the women's 1500m final of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 23, 2008. Iryna Lishchynska of Ukraine (3105) finished second in the event. REUTERS/Gary Hershorn (CHINA)

Nancy Jebet Langat of Kenya gestures as she crosses the finish line to win the women's 1500m final of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 23, 2008. Iryna Lishchynska of Ukraine (3105) finished second and her compatriot Nataliya Tobias (3069) third in the event. REUTERS/Gary Hershorn (CHINA)

Athletes compete in their women's 1500m heat of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 21, 2008. Running next to Corrigan is Iryna Lishchynska of Ukraine. From left: Lisa Dobriskey of Britain, Sylwia Ejdys of Poland, Nancy Jebet Langat of Kenya, Anna Alminova of Russia, Nataliya Tobias of Ukraine and Shannon Rowbury of the U.S. REUTERS/Jerry Lampen (CHINA)