World record-holder Kaylee McKeown ramped up preparations for the defence of her Olympic 100m backstroke crown with the second-fastest swim of all time on Tuesday.

The 22-year-old blitzed home at the Australian Olympic trials in 57.41secs, just shy of her world-record 57.33 and ahead of Mollie O'Callaghan who became only the fourth swimmer ever to dip below 58. O'Callaghan's 57.88 in Brisbane was enough to also easily qualify, but she may not swim the event in Paris this summer given her likely heavy freestyle and relay schedule.