The United States broke the world record for the second time in as many days in the mixed 4x400m as Michael Cherry anchored the squad to a new benchmark of 3:09.34*, taking almost three seconds off the first-round performance and delivering a 12th world gold to their second-leg runner, Allyson Felix.
The US had swapped their entire quartet of world record breakers from the previous day, bringing in four runners who had missed individual places but were selected for the men’s and women’s relay squads. The effort earned the team a US$100,000 bonus as part of the world record programme supported by TDK.
Silver in an event that will make its Olympic debut in Tokyo next year went to Jamaica in a national record of 3:11.78, and Bahrain, fielding world 400m silver medallist Salwa Eid Naser, took bronze in an Asian record of 3:11.82.
Poland was the only team to diverge from the man-woman-woman-man format, seeking to create a lead through male runners Wiktor Suwara and Rafal Omelka that could be maintained by their two new women runners – Iga Baumgart-Witan and Justyna Swiety-Ersetic, both members of the victorious team at last year’s European Championships in Berlin.
It was a gamble that captured the attention of the crowd, who roared their support as the slight figure of the Pole set off with seven men in pursuit.
But the gamble failed to pay off as the 30-metre lead Omelka handed to Swiety-Ersetic proved insufficient.
Cherry swept by the individual European champion halfway down the back straight, Javon Francis of Jamaica was the next to pass, and the teams from Bahrain and Great Britain & Northern Ireland also got past her before the line.
The British squad, anchored by two-time European champion Martyn Rooney, finished fourth, improving their European record to 3:12.27, and Poland’s boldness at least gained them a national record of 3:12.33 in fifth place.
The first round had produced a world record as the US quartet of Tyrell Richard, Jessica Beard, Jasmine Blocker and Obi Igbokwe had reached the final in 3:12.42.
At that point the new line-up was employed, with Wil London handing over to Felix, who passed to Courtney Okolo, who then sent Cherry on his way.
The victory means that, at 33, Felix now has a dozen world golds in five different events: 200m, 400m, 4x100m, 4x400m and the mixed 4x400m.
Mike Rowbottom for the IAAF
* pending the usual ratification procedures