Aaron Peirsol overshadowed Michael Phelps' first appearance at the US National swimming championships on Wednesday, reclaiming his 100 meters backstroke world record with a stunning swim. Peirsol clocked 51.94 seconds, slicing .44 seconds off the mark set by Spain's Aschwin Wildeboer Faber in the lead off leg in a 4x100m medley relay at the Mediterranean Games on July 1. Matthew Grevers had taken the race out in world record pace and led Peirsol at the turn but the Olympic champion took command over the final 50, pulling away for the win and securing his spot for the world championships in Rome later this month. While Peirsol stole the spotlight, it was Phelps, the winner of 14 Olympic gold medals, the capacity crowd had come to see. Phelps delighted his fans picking up wins in the 200 freestyle and 200 butterfly. In other races, Dana Vollmer won the women's 200m freestyle in 56.20 ahead of Allison Schmitt (1:57.25), while American record-holder Katie Hoff finished eighth. Hayley McGregory made up for past disappointments with a victory in the 100m backstroke that sealed her spot on the world team. McGregory won in 1:00.07, ahead of 15-year-old Elizabeth Pelton. Canadian breaks record Teenager Amanda Reason broke the world record in the women's 50-meter breaststroke (clocking 30.23sec) on Wednesday at the Canadian trials for the world swimming championships.