Olympic gold medalist Michael Phelps is trying a midcareer shift. He has shelved events such as the 400-meter individual medley, which he has dominated for nearly a decade, to involve himself in shorter races, including the 100 freestyle, according to media reports.

U.S. swimmer Michael Phelps prepares to compete in the men's 100 meter freestyle event during the Santa Clara International Grand Prix swim meet in Santa Clara, California June 14, 2009.[Xinhua/Reuters Photo]

At the U.S. swimming championships that begin Tuesday and at worlds in Rome this month, Michael Phelps will perfect his skills in shorter games.

In recent warm-up meets, he has won the 100 freestyle once and finished second twice. He has set a personal best in the 100 butterfly but also has finished second twice in the 100 backstroke.

"It's going to be really difficult for him," says swimming analyst Rowdy Gaines "I think it takes a tremendous amount of courage, swimming-wise, to step out of your comfort zone."

"I have unfinished business," Phelps said Monday. "When I look back on my career, I want to say I did everything that I wanted to do."

"In the 100 free, I know I'm not the best. But if I have the opportunity to step up and race the best, that's something I've always enjoyed,"

At this week's U.S. championships, Phelps is entered in the 100 and 200 freestyle and the 100 and 200 butterfly. The top two finishers in each event at nationals will qualify for worlds.

Phelps won a record eight gold medals at the 2008 Summer Olympics in Beijing, China, four years after he won six gold medals at the Summer Olympics in Athens, Greece.

(Agencies via Xinhua News Agency July 7, 2009))