Michael Phelps won the 18th gold of a mind-boggling career in the 4x100 metre medley relay on Saturday, retires with twice as many golds as any other Olympian.
The United States set a short course world record of three minutes, 25.09 seconds in the men's 4x100 metre individual medley relay at the world championships on Monday.
Brendan Hansen has broke the 200 metres breaststroke record at the US trials.
Americans Michael Phelps and Brendan Hansen broke their own world records at the Pan Pacific Championships.
American Brendan Hansen broke his own world record in the men's 100 metre breaststroke at the US swimming championships.
The 21-year-old is hoping to provide Japan with their first male Olympic champion since Daichi Suzuki won the 100m backstroke in 1988.
Brendan Hansen has broken the world record for 100 metres breaststroke on the second day of the U.S. Olympic swimming trials.