South African Penny Heyns said one breaststroke world record was a surprise, but two at this stage of the season was downright amazing.

"Never in my wildest dreams did I think I would do this," Heyns said after she twice lowered the 200 metres breaststroke world record on Saturday at the Janet Evans Invitational at the University of Southern California.

"I lifted weights on Monday, and I've been training hard. This is almost scary."

Heyns, the 1996 Olympic gold medallist in the 100 metres and 200 metres breaststroke, added the 200 metres breast world mark to her records at 100 metres and 50 metres in her signature stroke.

In the morning preliminaries, she broke Australian Rebecca Brown's five-year-old mark of 2:24.76 with a time of 2:24.69. She followed up with a 2:24.51 in the finals.

Heyns, competing in the meet for the University of Calgary, saw fellow South African Ryk Neethling win his third individual event of the meet, the 200 metres freestyle. He had already won the 400 and 800 metres free.