U.S. sprinter Allyson Felix

United States' Allyson Felix celebrates her in win the women's 200-meters during the athletics in the Olympic Stadium at the 2012 Summer Olympics, London, Wednesday, Aug. 8, 2012.

Allyson Felix of the United States celebrates after winning gold in the Women's 200m Final on Day 12 of the London 2012 Olympic Games at Olympic Stadium on August 8, 2012 in London, England. (Photo by Ezra Shaw/Getty Images)

Allyson Felix of the United States celebrates winning gold in the Women's 200m Final on Day 12 of the London 2012 Olympic Games at Olympic Stadium on August 8, 2012 in London, England. (Photo by Paul Gilham/Getty Images)

Allyson Felix of the United States celebrates after winning gold in the Women's 200m Final on Day 12 of the London 2012 Olympic Games at Olympic Stadium on August 8, 2012 in London, England. (Photo by Stu Forster/Getty Images)

Allyson Felix of the United States celebrates after winning gold in the Women's 200m Final on Day 12 of the London 2012 Olympic Games at Olympic Stadium on August 8, 2012 in London, England. (Photo by Ezra Shaw/Getty Images)

Allyson Felix of the United States celebrates after winning gold in the Women's 200m Final on Day 12 of the London 2012 Olympic Games at Olympic Stadium on August 8, 2012 in London, England. (Photo by Michael Steele/Getty Images)

Allyson Felix of the United States celebrates after winning gold in the Women's 200m Final on Day 12 of the London 2012 Olympic Games at Olympic Stadium on August 8, 2012 in London, England. (Photo by Quinn Rooney/Getty Images)

Allyson Felix of the United States celebrates after winning the Women's 100m during the Seiko Golden Grand Prix Kawasaki at Todoroki Stadium on May 6, 2012 in Kawasaki, Japan. (Photo by Kiyoshi Ota/Getty Images)

Track athlete, Allyson Felix poses for a portrait during the 2012 Team USA Media Summit on May 13, 2012 in Dallas, Texas. (Photo by Ronald Martinez/Getty Images)

Jeneba Tarmoh (L) and Allyson Felix look on after competing in the women's 100 meter dash final during Day Two of the 2012 U.S. Olympic Track & Field Team Trials at Hayward Field on June 23, 2012 in Eugene, Oregon. (Photo by Michael Heiman/Getty Images)

Allyson Felix competes in the women's 100 meter dash semi-final during Day Two of the 2012 U.S. Olympic Track & Field Team Trials at Hayward Field on June 23, 2012 in Eugene, Oregon. (Photo by Andy Lyons/Getty Images)

Allyson Felix of the USA wins the 200m at the Samsung Diamond League Prefontaine Classic at Hayward Field on June 2, 2012 in Eugene, Oregon. (Photo by Craig Mitchelldyer/Getty Images)

Track athlete, Allyson Felix poses for a portrait during the 2012 Team USA Media Summit on May 13, 2012 in Dallas, Texas. (Photo by Ronald Martinez/Getty Images)

Track athlete, Allyson Felix poses for a portrait during the 2012 Team USA Media Summit on May 13, 2012 in Dallas, Texas. (Photo by Ronald Martinez/Getty Images)