CHICAGO (CBS) — Mixed martial arts will be the main event at the Chicago Theater on Thursday.

The upstart Professional Fighters League held an outdoor workout on State Street on Wednesday for a little PR punch.

CBS 2’s Megan Mawickie has the story of a female Olympian making her MMA debut.

“I’m a little bit insane, for sure. I’m definitely insane.”

Kayla Harrison said that because she’s going from an Olympic mat to a cage.

Harrison reached the pinnacle of judo.

She’s the first American woman to win two gold medals at the Olympics.

Now she’s starting over, hitting the mixed martial arts world.

“I spent a lot of time after the Olympics doing some soul-searching,” said Harrison. “I knew that I was done with judo. I knew that I was burnt out but I didn’t want my athletic career to be over and I knew I wanted a new challenge. Let me tell you MMA is really a challenge!”

There are similarities between MMA and judo but many differences. The biggest adjustment for Harrison?

“I would say getting punched in the face,” laughed Harrison. “Most days it goes OK. Some days I don’t move as much as I should and then I become one of those bobble heads.”

A few other Olympic medalists have crossed over into MMA, most notably Ronda Rousey. But don’t compare Kayla to Ronda.

“(Am I) tired of it, yeah. I’m not going to lie. I’ve moved to Boston when I was 16. She was there training. She was my roommate, my teammate for years. When I was young, I wasn’t the star in judo, she was,” said Harrison. “I wanted the coach to pay attention to me so I had to work harder. She’s always been sort of this rabbit that I’ve been chasing.”

Harrison said she’s got range of emotions as she enters a new arena.

“I’m definitely nervous. I’m putting everything on the line, my reputation, everything that I’ve worked for,” said Harrison. “And I’m anxious to see how I deal with a new set of pressures.”