Ryan Lochte of the United States has set the first individual world swimming record since hi-tech bodysuits were banned at the start of 2010.
He won the 400m individual medley at the World Short Course Championships in Dubai in 3:55.50 - nearly two seconds faster than the previous mark.
Russia's men set the 4 by 200 freestyle world record, shaving more than two seconds off the previous best time.
With China's women swimming to a new record in the 800m freestyle relay, only three new world marks have been set since the ban was introduced - all in Dubai.
In 2009, 29 world records were set in the first five days of the Fina World Championships in Rome.