Eighteen-time Olympic gold medallist Michael Phelps won the 100m butterfly at the USA National Championships in a world-best time - a day after doing the same in the 200m butterfly.

Multiple Olympic champion Michael Phelps sent a message to his fellow competitors by posting the fastest time of the year in the 200 meters butterfly at the U.S. Nationals on Friday.

The women are getting it done at the world swimming championships.Sarah Sjostrom of Sweden lowered her own world record in the 100-meter butterfly to win gold Monday night, and then Katinka Hosszu of Hungary erased a world mark from the high-tech suit era to claim the 200 individual medley.