LaShawn Merritt crosses the finish line first, in the men's 4x400-meter relay at the IAAF World Athletics Championships in Daegu, South Korea, Sept. 2. Once banned for doping, Merritt has been cleared to run in London next summer.

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South African runner Oscar Pistorius, right, runs in the 400 meter race in France, July 8, 2011. His time in a race in Italy Tuesday was good enough to send him to the World Championships. Franck Fife/AFP/Getty Images hide caption

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