Salespeople say that running, lifting weights, carrying excess pounds, even the simple act of sitting in a chair all day can exaggerate the compressive force of gravity on the disks, which tend to shrink as much as a half-inch during the day and, like sponges, rehydrate during sleep. The theory is that the devices can help ease this daily toll on the body.
With those caveats in mind, here are four takes on spinal decompression devices that claim they've got your back.
--Roy M. Wallack
Teeter EP550 Inversion Table: A pivoting bed with ankle clamps that can tip you into a head-down, feet-up position.
Likes: Easy, relaxing and safe to use; slip your feet under the ankle pads and lean back. Adjustable-height bed accommodates bodies ranging from 4 feet, 9 inches to 6 feet, 6 inches. Teeter claims that vertical inversion is more effective than horizontal traction, citing a study that suggests only a near-vertical body position fully decompresses and rehydrates disks. The EP550 is easier to use and more effective than hanging hands-over-head, à la pull-ups, which is also effective but too difficult for most people to do for a length of time and without muscular stress. Recommended use 3 to 5 minutes. Only device to offer "progressive decompression" -- a variety of head-down positions, from angled to full vertical.
Dislikes: Limited fitness use; lets users do just one exercise (reverse squats). Takes some acclimation. I don't have high blood pressure, but my head wasn't happy. And you'd better not eat soon beforehand; I felt my sardine lunch for an hour afterward.
Price: $359. (800) 847-0143; www.teeter-inversion.com.
Body-Solid Tools Inversion Boots: Traditional low-tech padded ankle holders with hooks that suspend you upside-down from a pull-up bar.
Likes: Simple, easy to use, good vertical decompression, allows you to do several fitness exercises, including ab crunches, back extensions and reverse squats. Includes single-action locking mechanism with built-in safety lever; thick, contoured support pads; and extra pads to fit various users.
Dislikes: You need a high bar several feet taller than your body height to get full arm extension. No adjustability, like the Teeter board; you only hang straight down.
Price: $99 (pull-up bar not included). (800) 833 1227; www.body-solid.com.
Spinal Stretch: Waist belt-ratchet device that attaches to a door jam and is worn while lying on the floor. Extra back friction pad prevents slipping forward on the carpet.
Likes: Convenient and less scary for people who don't like being upside down. Put strap in door jam, cinch up waist belt, put friction strap around upper back and -- from a prone position -- begin pushing-pulling the telescoping ratchet handle back and forth, tightening the strap. That pulls your hips toward the door while the friction strap keeps your back in place, stretching your back. Device is transportable in its tough, 18-inch-long nylon bag. Practical too; allows you to watch TV or read a book as you stretch, which you can't do hanging upside down. Recommended stretch time: 15 minutes.
Dislikes: Won't work on a wood or tile floor. Does not seem to stretch you out as much as the inversion devices. The pulling on the hips may be a bit uncomfortable at first. Don't go crazy on over-ratcheting it; I went too far and tore the strap.
Price: $149. spinalstretch.com.
Half rack, full back
Teeter Dex II: Hip-supported inversion device that locks in place behind the knees, forcing your legs to form a 90-degree angle and leaving your upper body to hang vertically.
Likes: Very user-friendly. Easy way to invert if you are not comfortable hanging from your ankles. You can't hyperextend the back. Doesn't require a lot of adjustments; lets users perform back extension and ab exercises.
Price: $399. (800) 847-0143; www.
Wallack is the author of "Run for Life."