For the past several years, all things extra have reigned in the fitness world. HIIT classes in a 45-degree mock ski lodge? Architecturally ruffled sports bras? Been there, took barre class in that.

And while all this newness has served our novelty-seeking natures well, it appears the pendulum is starting to swing back to the classics. (I mean, even Well+Good’s style guru is working out strictly in black, unadorned leggings these days.) On the exercise front, the biggest indication that we’re seeing a return to fuss-free fitness is that the treadmill—yes, the same device collecting dust in your parents’ spare bedroom—is rapidly become the cool kid of the boutique workout scene.

Of course, treadmills have been part of the studio landscape for a while now, mainly as part of an ensemble cast of equipment at Barry’s Bootcamp, Orangetheory, and other interval-training destinations. But it’s only more recently that they’ve started acting as headliners in their own right, with treadmill-centric studios popping up from coast to coast. New York City has Mile High Run Club, in Los Angeles there’s Stride, while Runn, RacePace, and MyStryde represent the category in Chicago, Houston, and Boston, respectively.

David Siik, creator of Equinox’s Precision Running program, isn’t the least bit surprised by this development. “People have more choices than they’ve ever had in history, and whenever you have a lot of choice, it can become overwhelming,” he says. “We have so many awesome group fitness experiences, but people are getting really hungry for that return to basics, that feeling of showing up for track practice.”

“People are getting really hungry for that return to basics, that feeling of showing up for track practice.”—David Siik, Equinox

Fitness historian Natalia Mehlman Petrzela agrees. “I think [treadmills’] popularity is part of a reaction to some of the fanciness and complexity of the fitness world,” she says. “It’s making some people seek out simpler forms of exercise, whether it’s pickup basketball or just running on the treadmill.”

The numbers back up this hypothesis. For example, Peloton reports that it’s completely sold out of the first wave of its $4,000 treadmill, Tread, which launches this fall. The brand also tells me that Tread preview classes at its New York City studio are consistently sold out, and the same goes for Equinox, where Precision Running classes—450 of them on schedules at clubs across the globe—are the most popular group fitness offering at the gym.

And then there’s the fact that treadmills have long been the best-selling category in exercise equipment, with a market five times larger than the stationary bike market, a stat that’s frequently cited by Peloton CEO John Foley. With this in mind, is it any wonder that this run-of-the-mill (wink!) piece of gym equipment is primed to undergo a serious image makeover, like indoor cycling and Pilates Reformers before it?

From torture device (yes, really) to high-tech darling

Treadmills haven’t always been so covetable. In fact, says Petrzela, they were actually used as devices to power hard labor—and even inflict torture on prisoners—back in the 18th and 19th centuries. (Talk about a “dreadmill.”)

It wasn’t until the 1970s that treadmills really took hold as a fitness device. “The first affordable home treadmill retailed for about $399 and was rudimentary, featuring wooden rollers and a single on/off switch,” says Petrzela. “The early jogging craze had a decidedly low-tech, back-to-the-land vibe, but ironically became a national pastime thanks in part to this clunky machine that enabled Americans to hit a treadmill at home or in the health clubs.”

The treadmills of today are the opposite of analog, which is part of the reason why we’re so fascinated by them right now. “Treadmills have come a very, very long way in the last 10 years,” says Siik. “I always equate it to cellphones. Imagine the first cellphone you ever had and think about the one you have now.”

Using this logic, the treadmills used in Equinox’s Precision Running studios are the equivalent of the iPhone X. Exclusive to the brand, they were custom built specifically for the class’ quick-change, interval-style format, with features like a one-touch button that slows the treadmill to your desired recovery speed and the fastest rates of deceleration in the industry. (Translation: No holding on for dear life as you wait for your sprint speed to subside.)

Technogym’s new Skillrun treadmill, introduced earlier this year, is upgrading the run class experience at NYC’s Mile High Run Club and Life Time at Sky. Ideal for those who get bored with traditional indoor runs, it’s designed so that you can mimic pro-athlete exercises like sled pushes and parachute runs with no additional equipment, and its biofeedback technology tracks stats like endurance, agility, and strength in real time.

And then there’s Peloton’s Tread, which was created with comfort in mind. It’s got a shock-absorbing belt that reduces the impact of each stride, two simple control dials that allow you to change your speed and incline, and a 32-inch HD touchscreen with digitally enhanced sound so you can feel fully immersed in the brand’s live or on-demand classes.

Running gets the boutique fitness treatment

The new wave of high-tech treadmills may be capturing people’s interest, but the accompanying rise of boutique running classes is keeping them hooked.

These classes generally fall into one of two camps. Some have a festive, party-like atmosphere—ideal for those who get bored with running. Rumble Boxing’s first dedicated treadmill studio will look a lot like this when it opens in NYC in 2019. “We want to make running and strength training fun. Period,” says Rumble co-founder Noah Neiman. “Expect elevated designs, custom Rumble Treading music, and a maniacal attention to elevating the fun factor for the client.” (Not that you won’t also break a serious sweat—Neiman says that the high-level training you’ve come to expect from Rumble Boxing will carry over to its treadmill studio, too.)

The new wave of high-tech treadmills may be capturing people’s interest, but the accompanying rise of boutique running classes is keeping them hooked.

At other studios, however, entertainment takes a back seat to education. At Equinox’s Precision Running labs, this tactic has been drawing in all levels of runners, from absolute beginners to experienced athletes.  Take the music, for instance—about 70 percent of the class soundtracks are made up of non-lyrical tunes, so Drake’s voice isn’t competing with that of the coach, who is constantly doling out tips to help make students into better runners.

Lighting, too, is carefully considered based on studies of chromotherapy (AKA the use of colored lights to change your physical state). “The light experience supports the content—it’s never distracting,” says Siik. “We average about 110-115 light changes per workout, and each workout has its own light signature, programmed to have the perfect fades and color shifts from the sprint to the recovery.”

On-demand running workouts are also luring boutique fitness fans back onto the treadmill. Apps like Studio and Aaptiv deliver audio-only versions of boutique fitness classes, complete with music, leaderboards, and instructor cues. Peloton’s Tread, on the other hand, is going the video route. Its screens will stream four different class formats—Bootcamp, Running, Walking, and Floor— with 12 new classes set to be introduced each day.

Peloton co-founder and COO Tom Cortese thinks that the out-of-studio approach to treadmill workouts is primed for major growth in the years to come. “It’s hard enough to get yourself to the gym, and it’s even more challenging when you have to schedule a workout a week or two in advance because your class with your favorite instructors books up within a couple hours,” he reasons. “It’s much easier to work out on your time, in the comfort of your own home.”

No matter how or where you take a running class, one thing’s for sure: It’s been scientifically proven over decades to transform your mind and body, and that might just be the biggest part of its appeal. “People are desperate right now to have the most efficient workout possible,” says Siik. “And the most fundamental physical activity known to mankind is the act of running.” No equipment required—except for a snazzy new treadmill, that is.

Ready to lace up your running shoes? Try this treadmill hack for a serious booty boost, and check out these tips for making your treadmill workout more effective from a Peloton Tread trainer.