Racers follow the stream -- jumping off small cliffs and through waterfalls -- and a final rock face at the base creates one of the last challenges, requiring concentration and crab-walking to climb down.

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Aly Raisman didn't use one in Thursday's all-around final, which her coach, Mihai Brestyan, called a strategy to sharpen her concentration.

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But just as striking for me has been the experience of sitting no more than a metre and a half away from Oscar Pistorius - able to hear his breathing patterns, his sobs, muttered prayers, and to see the muscles strain on his neck as he stares forward, with the concentration you would expect from someone braced for the start of an Olympic final.

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In truth, Jankovic's final steps to victory had more to do with the 12-time Grand Slam champion's lack of concentration than her own mental fortitude.

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