Six-time Olympic gold medallist Sir Chris Hoy decided to retire from cycling after using "every last ounce of energy and effort" at London 2012.
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America's Shawn Crawford, the 2004 Olympic 200m gold medallist, has been banned for two years for not complying with out-of-competition drugs testing.
The US Anti-Doping Agency (Usada) said the 35-year-old had failed to provide details of his whereabouts for testing on three occasions within 18 months.
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