Art by Sam Woolley

The gym looked like a South American greenhouse: paned with glass, painted in greens ranging from pastel to neon, studded with tropical foliage, an unevenly paved brick patio sprouting weeds, all surfaces blanketed in a thin film of dust. Everything was highly functional but had the vague look of disrepair, just enough to be charming. It was a jungly reprieve from the industrial cementscape it sat in, and the workout I’d come for, similarly, was a reprieve from all the bars and weights and pulleys of most gym experiences—just me, a strap hanging from the ceiling, and my own body weight.

That reads as a little morbid, so, to clarify, this was TRX, the overzealously branded Total-body Resistance eXercise, a device for suspension training—a style of bodyweight exercise with an aspirational gymnastics vibe. Don’t fret if you cannot suspend yourself from two hanging rings with your Olympically swole tree-trunk arms, though, because the TRX device has a milder learning curve. It consists of a sturdy nylon strap, anchored to some fixed point overhead, which dangles down and forks out into two smaller straps with handles you can either grip with your hands or hook your feet into. (Think of an upside down “Y” whose two points you can reach out and grab.) Instead of hoisting large metal objects and moving them up and down to create resistance, you adjust the height of these straps and creatively slot your extremities into them, then let gravity to supply all the resistance. Envision doing a plank, but with your feet looped in, floating a foot or two above the floor instead of toe-planting firmly onto it. Or: grabbing two handles hanging a little below waist level, then leaning back into a kind of “trust fall” with your new nylon friend, until your arms are straight out in front of you and your body cuts a 45-degree angle with the floor. Then start bending at the elbow to get back upright—an inverted rowing motion.

Image via YouTube

This simple tool for elaborate fitness dates back to at least 1997, when Navy SEAL Randy Hetrick was looking for a improvised, portable bodyweight training regimen after he and his peers tired of vanilla pushups and situps. Using either a jiu-jitsu belt or part of a parachute harness—pick one of the two pat origin myths he’s offered—he ginned up a prototype he then called “the gizmo” and now probably calls “the seed for my sweet, sweet fitness empire doing $50 million in annual revenue.” TRX claims the equipment opens up hundreds of potential exercises, and it now dominates the suspension training market, which it invented, or at least singlehandedly popularized. Drew Brees is an avowed devotee, it attained trend piece status back in 2007, and these days it can be found dangling from the ceiling of most luxe gyms, including the lush one I recently wandered into. In that first class, led by a statuesque yogi with a placid demeanor and James Harden beard, we embarked on the most rigorous exercise I’ve ever attempted while partially dangling from the ceiling.

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What good was that hour of exertion? Part of the pitch of suspension training that you work on unstable surfaces and thus build up stability, a concept I’ll later circle back to but that for now, like other buzzy exercise concepts, might merit an eyebrow raise. But on the level of physical sensation: yes, you certainly feel unstable. Only during rest phases do your four limbs return to the ground and enjoy all that earthy relief. TRX intensive is highly recommended for those who enjoy slathering an exercise mat with sweat while barely moving, and those who enjoy feeling their whole torso roil with ache for extended periods of time. Performing movements like push-ups and knee-tucks while your feet are suspended from straps demands a lot of work from all the twitchy little far-flung regions of your core muscles just to keep you from collapsing.

If you’re unfamiliar with the concept of the core, let that be an early indicator you should avoid this sort of class altogether; despite the company’s assurances that their equipment suits all fitness levels, plunging too eagerly into a challenging TRX session can get you hurt, according to the trainers and exercise physiologists I consulted. Come in with some decent core strength at the get-go, lest the first set of body saws reduce you to a spasming heap on the mat.

“If you don’t have the core strength to hold the proper form,” exercise physiologist and Rutgers University lecturer Joe Mason explained to me, “you’re going to overcompensate with other parts of your body.”

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Thus you might end up putting unwanted strain on joints like the wrist or shoulder. In one of the classes I attended, one guy, though generally fit, lost control of his core, sunk the better part of his body weight onto his arms, and wound up with a sore shoulder—a likely result when you spend most of an hour-long class hunkered down on palms or forearms. A separate risk is pulling a particular joint too far out of its range of motion. Neither risk is unique to TRX, of course. But in general, and especially without a knowledgeable eye to keep on eye on parts of the body overcompensating, most trainers said the risk/reward ratio of suspension training made it a poor choice for fitness novices. (NYC-based trainer Kate Bishop made the case that TRX straps are ideal for rehabilitation, because you can fine-tune exactly how much weight you want to load for any given exercise by adjusting strap height and body position.)

Image via YouTube

Now that you know how much it hurts and whether you should give up altogether, we can proceed to the potential benefits. Most feel predictable: muscle strength, endurance, balance, and potentially a nice dose of cardio, depending on how you choose to train. But the benefit that enthusiasts specifically ascribe to TRX above other exercises—and probably the benefit most up for scientific contention—is that TRX promotes “stability” by training on unstable surfaces.

Minnesota-based trainer Max Blochowiak laid out the debate and justified his own, pro-stability training stance: Some physiologists don’t believe that we have specifically evolved “stability muscles”and question the merits of even training on unstable surfaces. What we do have, however, are muscles in general, and exercises that put those muscles in unstable conditions demand more from them—causing more of those muscles’ individual muscle fibers to contract. Bishop similarly noted that this style of training yields desirable muscle “adaptations.” So in some sense, the chief danger of TRX is also its chief gift: it’ll make you feel uncomfortable and challenged, and make your muscles strain in ways unfamiliar. If you’re in decent shape and know to engage the right muscles in response, that can do you good, but if you’re wandering blind through all this you’re liable to tweak something.

For all my skepticism, I was satisfied by the range of options I got from this single black-and-yellow strap, which provided a mild warmup, stretching in novel poses enabled by the straps, brutal core work, an upper-body routine, and a conditioning circuit. For all this versatility and a welcome variant on the usual dull bodyweight exercises, it performs admirably for a long stretch of nylon. (Though, admittedly, nylon that’ll run you $150 if you want your own.) Things to bring to this class if you hope to succeed: a healthy core, an idea of what parts of your body you’re supposed to engage, an attentive instructor who can see if you’re overexerting yourself and compensating in dangerous ways, and a near-religious faith in the stability of that strap and whatever it’s attached to. At one point during a set of rows I leaned all the way down, glanced back, saw a gleaming pane of glass and a tumble to the street, and realized just how much the rest of my life relied on that steel crossbeam overheard.