World champions Dana Vollmer and Elizabeth Beisel followed up their Shanghai triumphs on Tuesday with national titles at the US swimming championships. Vollmer won the women's 100m butterfly, the same event she won last week at the world championships in China. She showed few signs of fatigue, winning in 57.26 just a day after arriving in California from Shanghai. "I didn't know how I'd swim," Vollmer acknowledged. "I tried to stay really hydrated on the flight. I ended up watching, like, four movies. I didn't really sleep." Beisel won the 200m medley in 2:10.75, edging Katie Hoff and Madeline Dirado. Beisel won the 400m medley in Shanghai. The championships serve as a qualifier for the Pan American Games and the junior world championships. Not all of America's swimmers opted to compete in the wake of their world championships campaigns, with Michael Phelps and Natalie Coughlin among those who chose to skip this year's nationals. Ryan Lochte, who won five gold medals and a bronze and set a world record in Shanghai, didn't qualify for the finals in his only event on Tuesday, noting just the 24th-fastest time in the 100m breaststroke. The relatively low-key post-worlds championships were an opportunity for Brendan Hansen to press ahead with his comeback plans, three years after he retired in the wake of a disappointing Beijing Games. Hansen, the former world record-holder, won the 100m breaststroke, bolstering a comeback bid that he hopes will take him to the London 2012 Olympics. He clocked 1:00.08 to win the national title he last held in 2008. "I have no doubt my best races are in front of me," Hansen said. "I have no doubt. "This sport is 90 percent neck up and that is clear for me right now. I have to respect the next 10 months and make sure I race as much as I possibly can so I'm more prepared than everyone else."