K-Swiss Inc.’s white leather shoes were once must-haves for players on the tennis circuit and stars of the hip-hop world. But the Westlake Village company’s sales have been sliding, so the shoemaker recently enlisted “Biggest Loser” trainer Jillian Michaels to try to get back into the game to promote a new model of footwear.

K-Swiss signed a multiyear deal earlier this month with Michaels, the tough-as-nails trainer on the NBC weight-loss reality TV show, to endorse the company’s Tubes running shoes.

David Nichols, executive vice president at K-Swiss, said Michaels is the ideal star to promote the lightweight running shoe that sells for $75. That’s because she started wearing Tubes earlier this year, before inking the deal with K-Swiss, while training contestants to lose weight on the “Biggest Loser.” She’s even told her Twitter followers about her love of the shoes.

“I am into the K-Swiss Tubes these days,” she tweeted before the company signed her. “They are built to compete with Asics, NB, and Brooks but are half the price.”

It’s just the message the company was looking for.

“Our mission is to be an inspiring and innovative sports brand,” Nichols said. “And she helps fulfill that inspiring part by motivating people and letting them know what they can do with the product.”

Nichols declined to specify terms of the deal. The campaign is scheduled to launch by back-to-school season, when Michaels will begin to appear in online ads and in stores to promote the new model.

The deal with Michaels is part of K-Swiss’ plan to reverse the downward slide, which dragged annual revenue from $509 million in 2005 to $241 million in 2009.

K-Swiss was founded in 1966 by two Swiss brothers who made a high-quality shoe for tennis players. The company’s classic white tennis shoes became popular among the country club crowd.

Sales for the company’s shoes began to slip in the late 1990s as tennis apparel went out of fashion. So the company started targeting urban youth, running ads in hip-hop magazines such as Source and Vibe that featured ethnically diverse teens wearing the white tennis shoes as casual footwear.

But even hip-hop stars such as Jay-Z and Lil’ Bow Wow, who helped K-Swiss become popular among stylish teens, couldn’t keep the brand hot forever. The shoes fell out of fashion in recent years, partly because the company has failed to update the design. Last year it launched the Classic Remastered that is supposed to be more comfortable than the original.

Meanwhile, K-Swiss has been retooling its image as a California company that makes quality performance footwear not only for tennis players but also for runners and triathletes – hence the signing of Michaels.

“They are rebranding themselves as the California company and they are trying to create a running category,” said Sam Poser, a senior research analyst in the New York office of Sterne Agee. “And the Jillian Michaels deal could do some good. It looks like it could be promising down the road.”

Indeed, as part of the deal, Michaels is set to collaborate with K-Swiss in the future on an apparel line.