Barely pausing for breath

Record breakers

Also impressing in 2018 were men's backstroke specialist Xu Jiayu and women's sprinter Liu Xiang

Xu, the reigning long-course 100 back champion, set a new 25m-pool world record of 48.88 over the distance at a World Cup meet in Tokyo in November, while Liu claimed the women's long-course 50 back mark by clocking 26.98 at the Asian Games.

Both results made the rest of the world's elite take note.

"You always assume with a guy like that they are going to be right there," US star Ryan Murphy said of Xu after pipping his Chinese rival to gold in the 100 in Hangzhou.

"He is really one of the best and he's got tons of talent. It's not easy to race a guy like him. He puts up a great fight every time."

Murphy owns the 100 and 200 backstroke golds from the Rio Olympics, but was beaten by Xu in the 100 at the 2017 long-course worlds.

And the American expects their seesaw battle to bring out their best.