KEY POINTS:
Natalie Coughlin broke the women's 100m backstroke world record, clocking 59.21s in preliminaries at the Grand Prix of Missouri long course swimming meeting.
Coughlin sliced 23-hundredths of a second off her own world mark of 59.44s, set in March last year in Melbourne, where she added the 2007 world title to the Olympic title she won in Athens.
