Remember what it was like to weigh 50 pounds? Nope, neither do we. But slip into a pair of skintight neoprene shorts, zip yourself into a pressure-controlled chamber, and prepare for lift off. Anti-gravity treadmills, like the AlterG, are taking the aches and pains out of cardiovascular training by “unweighting” runners from 20 to 100 percent of their bodyweight, one percent at a time.

But why defy gravity? According to the manufacturer’s claims, machines like the AlterG can reduce the risk of stress-related injuries, while allowing athletes to train harder, faster, and smarter in a safe, controlled environment. Sounds too good to be true? With Greatist’s outreach director (and resident running pro) Laura Schwecherl by my side, we headed uptown to see if going weightless was really the best new way to run.

Unload This — Breaking Down the AlterG

Photo by Jordan Shakeshaft

At the Upper East Side Equinox in NYC, we followed personal training manager Lindsay Dettbarn down a long row of run-of-the-mill cardio machines to find our “Back to the Future”-style ride. First up, Laura shimmied into the special AlterG shorts and climbed into the plastic covered “cockpit.” Once zipped in from the waist down, the machine began to do its thing, filling with enough air to lift Laura’s heels off the ground.

To our surprise, Dettbarn explained the NASA-developed technology doesn’t actually create a gravity-free chamber. The device relies on something called Advanced Air Pressure technology, which, after calibrating the user’s weight, allows a percentage of their bodyweight to lift up, up, and away from the high-speed Woodway belt. After a few basic drills, a customized interval workout — minus 50 percent of our bodyweight — launched us to speeds of 10 mph with relative ease. (On a regular treadmill I push 7 mph, on a good day.)

The only trouble was willing our feet back down to the belt with each step, and, amazingly enough, re-teaching the body to run in a straight line. (Feeling a little wobbly is common as the lower body gets accustomed to its new weightless environment, Dettbarn said.)

But training for speed isn’t the major sell of anti-gravity treadmills. Even though most NBA teams and U.S. Olympic Training Centers have them, AlterG’s marketing director told me, the AlterG functions first and foremost as a rehabilitation treadmill.

While few outside studies have tested the $32,400 machine’s merits, the anti-gravity treadmill was FDA-cleared for functional rehabilitation post-injury or post-surgery (specifically the hip, knee, ankle or foot)Use of an antigravity treadmill for rehabilitation of a pelvic stress injury.Tenforde, AS, Watanabe, LM, Moreno, TJ, et al. Department of Orthopaedic Surgery, Division of Physical Medicine and Rehabilitation, Stanford University, Stanford, CA. PM & R: The Journal of Injury, Function, and Rehabilitation, 2012 Aug;4(8):629-31.Use of an anti-gravity treadmill in the rehabilitation of the operated achilles tendon: a pilot study. Saxena, A, Granot, A. Department of Sports Medicine, Palo Alto Medical Foundation, Palo Alto, CA. Journal of Foot and Ankle Surgery, 2011 Sep-Oct;50(5):558-61.. The technology, which hit PT facilities in 2007, has also been approved for gait training, weight loss, aerobic conditioning, and sport-specific training (since the lightened load puts less stress on the joints while affording the same aerobic output).

During our run, Dettbarn was also able to accurately access — and correct — our running form, since in a weightless environment even the slightest adjustments seemed possible. And that’s good news when it comes to preventing future injuries from popping up.

Heading Down the Right Track? — The Takeaway

Photo by Laura Schwecherl

So does the road to recovery really start here? For an experienced runner like Laura, replacing some of her outdoor workouts with AlterG runs, at least in theory, could mean a reduction in the risk of overuse injuries (of which she’s suffered more than a few). And for me, the reward was more immediate: a pain-free run despite two recently herniated disks in my lower back.

The only real downside to defying gravity could be cost (prices vary, but some facilities offer a $100-200 monthly membership, while others price it per visit or per minute on the ‘mill). And then there’s accessibility; 1,000-plus units worldwide is plenty, but still doesn’t guarantee there’s an anti-gravity treadmill close by. There was also the issue of “coming back down,” the somewhat uncomfortable process of having your natural weight return — although that feeling will be different for everyone, pro athletes and elderly folks alike.

But perhaps the most interesting (and promising) candidates for the treadmill aren’t your average active individuals, but rather, sedentary people struggling with weight loss. “When I have a client who’s looking to lose a significant amount of weight,” Dettbarn told us, “I’ll have them step onto the [AlterG] treadmill and show them: ‘This is what it can feel like.’”

To find an AlterG near you, visit the AlterG website. Already experienced an anti-gravity run? Tell us your impressions in the comments below, or tweet Jordan directly at @jshakeshaft.