Boutique studios that offer a more personal approach to fitness and a softer ambience than big box gyms are a growing part of the $22.4 billion U.S. industry.

IHRSA, the International Health, Racquet & Sportsclub Association that is the trade association of the fitness industry, noted in its 2014 Health Club Consumer Report that personalized fitness studios, or boutiques, captured 21 percent of the market in 2013, which rose from $21.8 billion in 2012.

ModelFIT, a New York boutique studio co-founded by a trainer of supermodels that offers bulk-free fitness to clients on and off the runway, is an example of the customized fitness trend.

Despite the leggy lure of its name, fitness experts say the ModelFit workouts, which incorporate a mix of Pilates, yoga, balance, movement and stability training are based in science and suitable for all body types of women and the occasional man.

”We’re not pushing you to kill yourself at gym,” said co-owner Vanessa Packer, of the studio that does not feature the pounding music and sweaty culture that characterize many gyms.

Justin Gelband, a trainer and the director of the fitness classes at the studio has been dubbed “The Model Whisperer” for his work with Victoria’s Secret and Sports Illustrated models.

The fitness routines and exercises at the studio target small muscles that go unnoticed and unused. Workouts typically employ tools such as bodyweight, medicine balls, Pilates discs, and circuit training.

“Using those muscles lengthens, tones, and leans out the body, sort of sculpting it,” Packer explained.

Cardio-driven classes, like boxing which includes punching and kicking, also mix in other techniques like very light hand and leg weights, resistance bands and trampoline bouncing.

Although men are welcome, Packer said, the bulk of clients are women, both young and old.

Exercise physiologist Jessica Matthews said boutique studios' commitment to whole-body fitness is good science.

“I love seeing words like stability, mobility, movement training,” said Matthews, who teaches exercise science at Miramar College in San Diego, California. “The idea of spot reduction, or targeting one specific area is a myth.”

Like other boutique studios that focus on personal fitness and pitch to a certain audience, Matthews said Gelband's experience with models give it an added allure.

“We all want to look like that and he may be playing off that desire, but I’m optimistic that he imparts good knowledge,” she said.