Hurdles to clear

For the moment, the women's 400m hurdles world record stands at 51.90 seconds and belongs to 21-year-old Sydney McLaughlin. There's a heavy emphasis on "for the moment".

McLaughlin set the mark at US trials when she edged Dalilah Muhammad to earn the victory. McLaughlin's time was good enough to better Muhammad's old world record by 0.26.

"It's fun to be part of history and to be part of changing the women's 400 hurdles," Muhammad said. "I definitely think more is in store for me and definitely think Tokyo will be a good race."

In the men's version, Karsten Warholm of Norway will be the one to catch. The two-time world champion broke the world record on July 1. He finished in 46.70 seconds to eclipse the mark of 46.78 set by American Kevin Young in the 1992 Barcelona Olympics final. The world record could fall again in Tokyo with Warholm, Abderrahman Samba, who represents Qatar, and Rai Benjamin of the US all pushing each other.