Just 25 minutes after winning the 4x800m, USA added another set of gold medals to their collection at the IAAF/BTC World Relays, Bahamas 2015 by winning the 4x400m.
And, just as they had done in the longer event moments earlier, they broke their own competition record to successfully defend their title.
US indoor record-holder Phyllis Francis, who had clocked a sub-50-second split in yesterday’s heats, ran the opening leg this time and gave USA an early lead, covering the first lap in 51.40.
Natasha Hastings was challenged by 2014 Diamond Race winner Novlene Williams-Mills of Jamaica half way around the second leg, but Hastings kicked ahead to reopen the gap. Hastings covered her lap in 49.93 with Williams-Mills just a fraction slower, 50.02.
But the real damage was done on the third leg. Olympic champion Sanya Richards-Ross forged ahead with an incredible 48.79 lap. The one and only time she has ever run faster in a relay was at the 2009 IAAF World Championships, having won individual gold just days earlier
World indoor champion Francena McCorory already had a two-second lead before she started her anchor leg, but her 49.27 effort added another second to the USA’s winning margin. Their winning time of 3:19.39 was more than two seconds quicker than their winning time from last year.
Jamaica finished second in 3:22.49, almost four seconds ahead of the next team across the line. Britain’s Seren Bundy-Davies held off France’s Floria Guei on the last leg, the world bronze medallists finishing just ahead of the European champions, 3:26.38 to 3:26.68.
The remaining automatic qualifying places for the Rio 2016 Olympics went to Poland, Canada, Australia and Brazil.
Jon Mulkeen for the IAAF