10 August 2012 Last updated at 20:40 GMT USA smash world 4x100m relay record to win Olympic gold By Sam Sheringham BBC Sport at the Olympic Stadium The United States shattered a 27-year-old world record to win gold in the women's 4x100m relay at London 2012. The team of Tianna Madison, Allyson Felix, Bianca Knight and Carmelita Jeter blazed round the track in 40.82 seconds, beating East Germany's record of 41.37, which had stood since 1985. Jamaica were second in a national record time of 41.41, with Ukraine third in 42.04 and Nigeria fourth.