American teenager Michael Phelps [ Images ] broke his own 200 metres individual medley world record again on Saturday as he became the first man to win five titles at a U.S. national championships.

The 18-year-old won the final in a time of one minute 55.94 seconds, taking .10 of a second off the previous record he set at the world championships in Barcelona [ Images ] on July 25.

It was the fourth time Phelps had lowered the record in the event in the last six weeks -- in total taking more than two seconds off Finn Jani Sievinen's 1:58.16 which had stood since 1994.

Saturday's success at College Park, Maryland came after victories in the 100, 200 and 400 metres freestyle and the 200 metres backstroke -- all in personal best times.

Two women -- Tracy Caulkins in 1978 and Natalie Coughlin last year -- have won five events at the U.S. nationals, while the previous men's best of four was shared by Johnny Weismuller, Mark Spitz [ Images ] and Tom Dolan.