Swimming: Peirsol heats upheading for worlds

American Aaron Peirsol broke his own men's 100m backstroke world record at the United States world championships trials yesterday.

The 21-year-old clocked 53.17s in Indianapolis to shave nearly three-tenths off his previous best set in the first leg of the men's 4x100m medley relay in the Olympic final in Athens last year.

Peirsol won three golds in Athens.