OMAHA, Neb. (AP) — Chase Kalisz qualified fastest in the 400-meter individual medley preliminaries Sunday at the U.S. Olympic swimming trials with Ryan Lochte trying to shake off the cobwebs on the meet's first day.

Kalisz (KAY-lish) out-touched defending Olympic champion Lochte to win their heat in 4 minutes, 11.86 seconds. Lochte was second-fastest in 4:11.98.

"My first race is always the worst one," Lochte said. "I didn't really press anything to full potential. There's a little juice left. There has to be."

Jay Litherland, who swims for Georgia, was third in 4:12.57.

At 31, Lochte is the oldest swimmer in the final. Tyler Clary edged his way in, finishing eighth in 4:15.41.

Michael Phelps dropped the grueling event in which he owns the world and American records. Kalisz is a training partner of Phelps in Tempe, Arizona, and the 18-time Olympic gold medalist has said he is always pushing Kalisz to get better.

"He's a great competitor," Lochte said. "He's the young buck. It's definitely going to be a good race."

Phelps begins his quest for a fifth Olympic berth on Monday.

The five fastest heats were swum from slowest to quickest, with the remaining heats to be swum at the end of the morning prelims. It was doubtful that swimmers from the later heats would bump any of the top-eight qualifiers out of the evening final.

In the women's 100 butterfly, Kelsi Worrell advanced to the semifinals as the top qualifier in 56.84 seconds, the fourth-fastest time in the world this year and a personal best for the 21-year-old swimmer at Louisville.

"I wanted to go under 57, that's for sure," Worrell said. "(Coach) Arthur (Albiero) just kept reminding it would come when it's time. This is a good time."

Defending Olympic champion Dana Vollmer was second-fastest in 57.50. Vollmer is trying to make her second Olympic team, this time as the mother of 15-month-old son Arlen who was in the stands.

"I kept wondering why I wasn't more nervous," Vollmer said. "It doesn't feel yet like I'm at trials, which is a good thing. It doesn't feel like it's the end-all that it used to be. It's just another meet. If I make the team, fantastic. If not, I go home to my son."

Cassidy Bayer, a 16-year-old from Alexandria, Virginia, competing in her first trials, was third-quickest in 58.91.

Zane Grothe topped the 400 freestyle heats in 3:47.03. The 24-year-old from Boulder City, Nevada, has never swum in a major international meet and finished 14th in the event at trials four years ago.

Conor Dwyer was second in 3:47.15.

In the women's 400 IM, Sarah Henry qualified fastest in 4:36.93, just ahead of 2012 Olympic silver medalist Elizabeth Beisel, who touched in 4:37.61.

"It's really nice to have that first swim out of the way. A lot of anticipation," Beisel said. "It felt real smooth and looking forward to tonight."

Maya DiRado, silver medalist at last year's world championships, advanced to the evening final in fourth at 4:38.54.

Kevin Cordes qualified fastest in the 100 breaststroke, leading 15 other swimmers into the semifinals in 59.05. He was one of five men to go under 1 minute in the prelims.

Cody Miller was second in 59.33. Michael Andrew, a 17-year-old who has already turned pro, advanced in fifth with a personal-best 59.96.