At some point during the “Shred” class at SLT Yoga, the Greatist Team realized we were not, in fact, practicing yoga. At least not the kind of yoga we were used to.

Ten of us were poised above shiny blue mats in plank position, our feet sliding a set of gliders back and forth behind us. We’d just come out of a sweaty warrior II pose in which we held a set of three-pound weights in each hand. Already, tears came when I thought about how sore I’d feel the next morning.

SLT Shred Yoga Photo by Jordan Shakeshaft

SLT (that’s “Strengthen, Lengthen, Tone”) is just one example of the growing number of fitness centers that offer new spins on traditional yoga classes — everything from dumbbell-enhanced poses to aerial inversions. Many of the instructors at these studios are former athletes or dancers; and they focus on taking standard yoga poses to a new level by infusing the sequences with moves from other athletic disciplines. The result is a class that gives more of a physical workout than your typical 45 minutes of sun salutations.

One of the most common examples of this trend is Power Yoga, a fast-paced take on Vinyasa flow developed by Baron Baptiste in the 1980s that has since spread to fitness centers all over the country. Then there’s Iron Yoga, touted as a more efficient workout, which incorporates weighted strength-training exercises into every pose. Some of the most popular yoga DVDs include yoga for weight loss and Jillian Michael’s “meltdown.” If yoga is already a workout, as some experts say it is, these classes capitalize on its fat-burning, muscle-building, endorphin-boosting potential. But with the addition of iron-pumping and grunting, are these “yoga” classes still yoga, according to those who teach more traditional styles?

Chatarunga? Let’s Just Call It a Push-Up

Like many instructors at high-intensity yoga classes, Erin Jacques, co-founder of SLT, came from an athletic background. A competitive runner in college, she earned a degree in exercise and physiology before becoming the National Yoga Director at Exhale Spa in New York.

The idea behind SLT struck her after she tried a workout that combined traditional yoga poses with more intense exercises like mountain climbers. It occurred to her that yoga, especially vinyasa flow, is already a cardio workout, and she remembers thinking it wouldn’t be hard to just “turn it up a little bit.” The result would be an easily modifiable workout that satisfied a wider audience: those who enjoyed yoga but wanted a more intense cardio workout, and those who liked getting their heart rate up but were looking for something relatively low-impact.

Jacques describes Shred as a “cardio class with a yoga foundation.” In our session, that meant only one child’s pose (toward the very end of class) and definitely no hanging out in deep forward bends. But Jacques places a huge emphasis on the concept of yoga flow — focusing on the breath and moving easily from one position to the next.

It’s not as though her students just grab a set of weights to supplement every yoga pose, she told me. “[There’s] kind of a certain sequencing involved in it.”

Jacques is hardly the only person to see the potential for a sweat session in between the Oms. Mary Fanto, who teaches power vinyasa in Los Angeles, says all styles of yoga are really just a bunch of basic exercise moves.

A former field hockey and basketball player, Fanto soon realized that yoga wasn’t much different from a standard gym workout. “Forget about the asana [poses] and forget about the fancy names for everything. And if you really just strip it down it’s basically a lot of push-ups, lunges, and squats.”

Mind-Body Connection

I must admit I expected to find more of a raging debate between yoga practitioners who adhere rigidly to the traditional series of poses and more modern yogis happy to hang from the ceiling while they salute the sun. But, in fact, almost every yoga instructor I spoke with saw these new forms of exercise as a positive development. All instructors talked about accessing the mind as well as the body, about finding a place of peace even in the middle of a heart-pumping workout.

Take Michelle Dortignac, a professional dancer who developed the Unnata Aerial Yoga program, taught at studios in New York City and across the globe. Unnata students go through traditional yoga sequences using a circus hammock suspended from the ceiling.

But while aerial yoga might conjure up images of flailing legs and newfound fears of heights, Dortignac told me her class is actually focused on finding inner peace, just like any other yoga practice. Students who aren’t used to practicing off the ground gain a “fresh and new perspective” and another way to access their minds.

In designing the Unnata program, “I wanted to embrace and honor the entire science of yoga and not just the physical asana part,” she said.

As for yoga classes that involve weights or strength-training exercises, Dortignac was equally enthusiastic. “A lot of these classes can help access or sort of interpret and translate yoga for different demographics of people,” she said. “So on that level I think they’re very helpful.”

These offbeat classes end up broadening yoga’s appeal to those who don’t see themselves as the chanting type. Instructors often eliminate the Oms and the explanations of the philosophy behind different yoga postures, leaving students to create their own spiritual side to the practice. With a set of weights in hand, people might not realize they’re actually in the process of becoming peaceful or centered — or slowly becoming a yogi.

Keeping the Faith

As for whether these classes dilute the traditional yoga practice, many instructors seem to agree that the concept of “tradition” in yoga is already ambiguous. The original yoga teachers who developed the practice have long since passed on, and most instructors no longer adhere so rigidly to the Hatha or Ashtanga practice. Some instructors tailor their lessons to the needs or preferences of the students who show up that day, meaning that every class is a different experience.

Ultimately, there may not be a single definition of “yoga” or even a most authentic style. According to Fanto, every student has to develop an individual practice. “What’s traditional for me,” she said, “might not work for you.”

Special thanks to Erin Jacques, Mary Fanto, and Michelle Dortignac for their contributions to this article.