Libby Lenton is yet to become a mother but the way she describes it, breaking a world record is a bit like childbirth.

"As soon as you see the time, all the pain goes away," Lenton said after smashing the 100m freestyle record in a semi-final at the Olympic swimming trials.

The 19-year-old powered to the wall in 53.66 seconds to drown the former world mark set by Dutch Olympic champion Inge de Bruijn in the same pool.

Lenton became the first Australian woman to hold the record since Shane Gould in 1972.

Gould and triple Olympic 100m freestyle champion Dawn Fraser were both at the Sydney Aquatic Centre for the record swim - Gould brought to tears, Fraser to her feet.

The last time Fraser held the world record was 40 years ago.

Lenton's time on Wednesday night was more than five seconds faster than Fraser's best of 58.9s.

Fraser said the Queenslander's swim had brought back memories.

"She's taken her goggles off and she's gone: `Oh my God, I've broken the world record. The reaction that she did was so very natural," the Olympic great said.

"You look at the time and you think that can't be it, it's not my time, there's a mistake in the time keeping.

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