RENTON, Wash. - Tanji Johnson has always been a woman to be reckoned with.

"I'm very much your alpha male-type female," she said.

But now she's taking her game to a whole new arena. Tanji is a cast member on the new NBC show "American Gladiators."

In real-life she is an unassuming personal trainer from Renton, but she says when the cameras come on she becomes "Stealth....They call me Stealth because I'm the bomb."

The show pits regular people against professional athletes like Tanji in a series of grueling "David vs. Goliath" physical competitions. The last "David" standing wins $100,000.

Hosts Hulk Hogan and Laila Ali say Tanji is a toughie.

"She had a little bit of an evil streak in her, it seemed like. She was really trying to take those contenders out," said Ali.

Tanji is one of the top-ranked fitness competitors in the world, not to mention an Air Force veteran.

Her personality is far from the overblown brute you see on the show. But while Tanji is sweet, she's no cupcake.

"Maybe that's what Leila was talking about with the whole evil...I'm really a nice girl but if you come into my arena you're going to get hit," she said.

Tanji is planning a move to Los Angeles soon to capitalize on her star power as "Stealth."

American Gladiator airs at 9 p.m. Sundays on KING 5.