Marcia Kilgore headshot

FitFlop founder Marcia Kilgore. Photo courtesy of FitFlop

"All of the hair on my body stood on end," Marcia Kilgore tells StyleList of how she felt when she came up with idea to create the FitFlop.

"I was sitting on a panel of experts, and we were talking about how women, with all the multitasking they have to do, can have difficulty trying to squeeze exercise into their lives."

Then the light bulb went off: "Everybody does a bit of walking -- what about a flip-flop?" Kilgore recalls. "It's not that expensive to make, it's lightweight, it's going to work your muscles more, it doesn't hurt, it's not messy, you can slip it on and off. Perfect!"

And so the FitFlop was born.

Now the brand is expanding with a line of shoes and boots. "[They] are engineered with a bit of wobble in their midsoles, so your leg muscles work harder during every step you take," explains Kilgore.

"I always say it's like walking barefoot on uneven grass or on sand. You don't really notice your muscles are working more, but they are."

A pair of the FitFlop Superboots in brown suede. Photo courtesy of FitFlop

Celebrity fans include Julianne Moore, who was photographed in the Happy Gogh clog. "The very first season [summer 2008], we created this crazy sandal with Kirna Zabete. It was a gladiator sandal in snakeskin and we had a black one, too. It was really 'Mad Max.' She was in the New York Post wearing them. She looks hot and a bit subversive."

This summer's most buzzed-about bride also likes the line. "Chelsea Clinton was in them the day before her wedding," Kilgore tells StyleList. "She was wearing the black suede Oasis sandal."

So what's next for FitFlop? "We're excited about the men's shoes, the men's sneakers," Kilgore says.

"You would not know there is some toning going on in there. They're really cute. You'll wear them constantly. Your other shoes will feel ashamed!"

In other shoe news, check out the collaboration between New Balance and J.Crew.