Natalie Coughlin and Hayley McGregory blitzed to back-to-back world records and Katie Hoff secured her second Olympic berth at the U.S. swimming trials in Omaha, Nebraska, on Monday.

Just two days into the eight-day competition, four world records have fallen as American swimmers engage in a cut-throat battle for places in the Beijing Olympic team.

With only the top two finishers in each event qualifying, the competition has been fierce.

Even though McGregory and Coughlin posted world records in the 100 metres backstroke preliminaries, that was only good enough to take them as far as the final.