MENDRISIO, Switzerland — Kristin Armstrong won the women's time trial at the road cycling world championships Wednesday, then confirmed she will retire after competing in this weekend's road race.

The reigning Olympic champion timed 35 minutes, 26.09 seconds over two laps of the 16.7-mile course, beating Noemi Cantele of Italy by 55 seconds. Linda Villumsen of Denmark trailed by 58 seconds to take the bronze medal.

"I can't think of any better way of saying goodbye to the sport," Armstrong said, cradling her gold medal with both hands as she spoke. "I had a little bit of motivation today. Now I hope another American can come out on top on Saturday."

The 36-year-old Armstrong dominated the 41-rider field to win her second time trial world title. The first came in 2006.

"It doesn't matter how many times you become world champion, it's always the best feeling in the world," Armstrong said. "I just wanted to focus on going as hard as I could possibly go."

Armstrong led at every time check and extended her lead the farther she went, recording an average speed of 28 mph. The effort on a hot day in the Swiss Alps left her slumped over her handlebars after crossing the finish line.

One year after a disappointing fifth at the worlds in nearby Varese, Italy, Armstrong said she'd had trouble motivating herself so soon after her gold medal triumph in Beijing.

"I wanted to support the sport and come back for the worlds," Armstrong said. "I had one year to prepare and I had a perfect day."

Cantele, who started three riders before Armstrong, said her coach told her with 3.11 miles left that she was setting the fastest time splits.

"I gave everything," the 28-year-old Cantele said through a translator. "The gold medal was pretty far away from me."

Defending champion Amber Neben of the United States finished sixth, trailing her teammate by almost 90 seconds. French veteran Jeannie Longo-Ciprelli finished 10th, one minute 48 seconds behind. The 50-year-old Longo-Ciprelli is a four-time champion.

Armstrong said she will return to the U.S. to help young riders develop their careers. She recently launched a cycling academy in her home city of Boise, Idaho, and will work with a professional team based in California.

"I will be helping young riders come over to Europe," she said. "I want to give back to the sport and spend some time at home."