Danielle Williams has the eye of a tigress.

A regular at a CKO Kickboxing studio in North Brunswick, N.J., and one that opened just over a year ago in Yardley, Pa., she's lost 40 pounds punching a bag.

"I come here after work to de-stress," said the 32-year-old college financial-aid adviser from Florence, N.J.

Williams has lots of muscle-flexing company.

Mini-fitness centers, such as CKO (Club Knock Out), SoulCycle, and Orangetheory Fitness, among others, are popping up throughout the suburbs and often at your local shopping center.

"It's a huge trend," said Todd Sussman, senior vice president of retail for Colliers International, who recently placed an I Love Kickboxing studio in Jenkintown, and is scouting locations in Delaware for 9Round Fitness, another kickboxing chain. "People want an experience, so you bring the gym closer to their homes with these boutique studios.

"It's really just grown in the past 24 months in places like Willow Grove, North Wales, Ardmore," he said.

Flexible class schedules, with some starting as early as 5:30 a.m., and ending as late as 9:30 p.m., along with small class sizes, have made these studios ideal for those with busy lives, or who want to skip the big gym experience.

Some people, especially those new to fitness, are intimidated by the big-box gym scene, said RipFit owner Deanna Mallozzi. Other studio clients "want a more elite fitness program to take it to the next level."

The 2,200-square-foot RipFit studio opened on July 1 at the Village Square Shopping Center on Route 202 in Blue Bell. It offers both indoor cycling and a boxing circuit.

Orangetheory, a franchise at the Moorestown Mall that opened in December 2014, is looking to open in Voorhees or Cherry Hill, said area manager Marvin Santiago, who oversees the Orangetheory studios in Moorestown and West Windsor, N.J.

"By 2017, we plan to have 1,000 studios," he said. "We have an aggressive plan to open several more in the Philadelphia suburbs."

An Orangetheory at Liberty Place in Center City opened a few months ago and ones in Paoli and Blue Bell appeared in the last year.

An Orangetheory client pays $8 to $28 for a session, is led by a certified trainer, and wears a heart-rate monitor during a workout to reach what's known as an orange zone - where the body achieves EPOC, or excess post-exercise oxygen consumption, where it is claimed to burn calories long after the workout.

CKO has 72 franchises throughout the country and is expanding, too.

The CKO studio in Yardley is set between Einstein Bros. Bagels and Michael's Jewelers at the Oxford Oaks Shopping Center.

The popularity of the UFC (Ultimate Fighting Championship), martial arts, and boxing is helping fuel CKO's popularity, said CKO Yardley co-owner Justin Lucci, who looks a lot like actor Lou Ferrigno.

"This is not a fighting gym," said Lucci, a former assistant strength coach for the Eagles. "This is for a total body workout and cardio conditioning. You train like [UFC fighters], but there's no contact here."

Three sessions cost $19.99 as a package. That includes your gloves. The studio advertises through social media and direct mail. Lucci often drives around in a tiny Smart car draped in the black-and-gold CKO logo to promote the brand.

He just signed a lease to open a CKO studio at the Doylestown Pointe Plaza shopping center in the fall. A Center City CKO at 16th and Chestnut Streets opened eight months ago, while one in West Chester debuted two years ago.

"We're doing really well here," Lucci said of the Yardley studio, which opened in May 2015 and attracts members from Lower Bucks County.

He said about 80 percent are women and range in age from 25 to 55.

Steven Gartner, managing director for retail services at commercial real estate firm CBRE Inc., placed SoulCycle's first Pennsylvania studio at Suburban Square in Ardmore in May.

"We are seeing our upscale customer come more spread out through the day, not just at traditional shopping times," he said since SoulCycle's debut on May 27.

Sussman said such studios also can reach profitability much easier than a massive gym because they have less overhead and labor, and attract more average Joe investors.

"These gyms need a lot fewer members, each one paying $50 to $200 (a year), to become profitable," Sussman said. "They don't have to advertise to the whole world, just those that live within a few miles."

A street-front location with great exposure was crucial, said Gabby Cohen, spokeswoman for SoulCycle, which originated in Manhattan a decade ago and doesn't advertise.

Ardmore is SoulCycle's 62nd location. A City Center site, at 113 S. 16th St. in Rittenhouse Square, is scheduled to open in the fall.

On a recent Sunday, Seth Caplan, 19, and best friend Grace Weiner, 20, signed up for a $30 SoulCycle class (a $3 shoe-rental fee is waived for the first session) in Ardmore.

Inside the studio was a large image of a winding road behind the five dozen bikes lined up in rows.

Once the session started, the room dimmed and loud, techno music played. Instructor Alexis Rose, a former backup dancer, talked over the music: "Push it! Push it! Feel the resistance."

For 45 minutes, Rose combined high-endurance cycling with a motivational talk about spirituality and self-acceptance.

"I loved the energy," Caplan said afterward. "It was so positive."

215-854-4184 @SuzParmley