Much to his relatives' disappointment, Jonathan Hamm has forbidden them from attending next week's U.S. Olympic Trials for boxing in Mobile, Ala. Though the event isn't far from his hometown of Atlanta -- and he hasn't seen his parents or siblings in eight months -- the heavyweight worried that he would be too nervous if they were in the stands.

It's not that Hamm isn't used to a public stage. The part-time resident of St. Paul played one season with the New Orleans Saints, two more in the Arena Football League and landed a leading role in the well-reviewed independent film "Big Fan," where he portrayed a football star who nearly beats an admirer to death. But making the Olympic team would trump all of that, particularly for a guy who only took up boxing 20 months ago.

Hamm has spent countless hours at St. Paul's Rice Street Gym, working with coach John Johnson to transform himself from a 6-7, 280-pound defensive end into a promising heavyweight. He can proudly name all the honors he's won so far: USA Boxing national champion, Upper Midwest Golden Gloves champ, Minnesota state USA Boxing champion, top-ranked super heavyweight at the Olympic Trials that begin Sunday. At this moment, though, he's focused solely on what lies ahead.

"It feels pretty good to have done those things, but you have to forget about it pretty quick," said Hamm, who is 25-1 in the amateur ranks. "I have so much more to accomplish. The goal is to win a gold medal at the Olympic Games and become a world champion.

"In football, you're representing a state or city. On the Olympic team, you're representing the whole USA. That alone makes this the biggest thing I've ever done in my life. It would be one of the ultimate accomplishments."

It would also be something of a surprise, considering Hamm's brief time in the sport. But his life has been full of surprises going back to his days at Clark Atlanta University. An art lover, Hamm majored in art education and studied 3-D design while becoming an all-conference and all-region defensive end at the NCAA Division II school.

Hamm signed with the Saints as a free agent in 2007. An injury derailed his NFL ambitions, but he moved on to play two seasons with the Arena Football League's New York Dragons. While in New York, he began appearing in commercials as a side job, including a SoBe Lifewater spot featuring ballet-dancing football players.

That ad gained Hamm, 27, his widest audience when it aired during the 2009 Super Bowl. His biggest part came when writer/director Robert Siegel began checking out New York-area football teams, looking for the right guy to play fictional Giants star Quantrell Bishop in "Big Fan."

As Bishop, Hamm got to flash his fists on screen in a scene where he beats up Patton Oswalt, the film's star. But he didn't feel destined for a career in acting, and football was winding down, too. In late 2009, a friend told him about All-American Heavyweights, a California training center that develops athletes from other sports into boxers.

Hamm had saved enough money from his other jobs to commit himself full-time to training. More importantly, he had the desire.

"Making that adjustment was the hardest thing I've ever done," he said. "In football, you always have teammates to help you. In boxing, it's just you and your opponent. If you get tired or hurt, you have to keep going, and there's a lot of pressure when you get into that ring. But it's been a real blessing to me."

A coach at All-American Heavyweights enlisted Johnson to help develop Hamm, who does most of his training at the Rice Street Gym with occasional sessions in California. In only a year, Johnson said, Hamm has transformed from a big, slightly clumsy guy with a good jab to an agile, chiseled 255-pounder whose style is well-suited to the amateur game.

"If he keeps working hard, he's going to be really dangerous," Johnson said. "He has the ability to be a world champion, and he wants to win. He understands what he's got to do."

Johnson hasn't able to travel with Hamm recently because he was injured in a motorcycle accident, so another Twin Cities trainer -- Adonis Frazier of Minneapolis' Circle of Discipline -- is filling in. Hamm now lists St. Paul as his hometown, though as a son of the South, he expects to fight better in Mobile's heat than he did while winning the U.S. title in the thin air of Colorado Springs.

In the distant future, Hamm plans to turn pro, then pursue yet another career as a designer of roller coasters. In the near term, he's hoping to extend his current thrill ride all the way to the London Olympics.

"When I first started, I thought making the Olympics was out of my reach," he said. "It would be amazing to represent the USA."

Rachel Blount • rblount@startribune.com