What you should know before you buy
Can a daily dose of electricity ease back pain? That’s the promise of transcutaneous electrical nerve stimulation (TENS) devices that are now sold on store shelves and heavily marketed in television and magazine ads.
Doctors, physical therapists, chiropractors, and other healthcare professionals have treated muscle and joint pain with professional TENS devices for years. But over-the-counter (OTC) TENS devices are now available, starting at around $25 per unit, and some products cost significantly more. Are they worth the investment? Do they truly offer a drug-free way to “block pain,” as their makers promise?
An old idea, renewed
Using electricity to relieve pain isn’t a new idea. Ancient healers employed its power by using fish-such as rays-that discharge electrical current to treat gout and other painful conditions. In the 18th century, electrotherapy machines were used for pain treatment. Interest in electrotherapy eventually waned, but returned in the mid-1960s, which led to the development of TENS devices and related pain-relief tools now used in healthcare settings.
Despite the recent hype about TENS, it was actually back in 2004 that the Food and Drug Administration (FDA) approved the first over-the-counter TENS device. Since then, wearable electrotherapy pain-relieving products have come on the market, many of them based on the same technology as TENS.
In theory, TENS blunts pain by delivering pulses of electrical current through the skin. These electrical signals activate nerves and trigger the release of endorphins, which are naturally occurring chemicals that block substances in the body that produce pain. TENS may produce other physiological changes that ease pain, as well.
TENS products come in a variety of sizes and styles. Some include a handheld control panel, with wires connected to small adhesive electrode pads, which you apply to the skin covering your sore joint or muscle. Using the handheld device, you control the intensity of the stimulation that’s applied by the pads. (Some devices allow you to regulate the frequency of pulses, too.) Wireless TENS devices are also attached to the skin using adhesive pads. The intensity of stimulation is regulated by remote control.
While TENS delivers electrical current, you don’t feel a shock; instead, the devices produce a tingling sensation that’s either mild or strong, depending on the intensity setting chosen. One popular TENS product has 63 different settings. Instructions typically recommend using TENS for 15 to 30 minutes, several times a day. However, some users leave the devices on longer.
Does it work?
It’s important to bear in mind that the FDA does not require TENS devices sold to consumers to undergo rigorous study to prove that they actually relieve pain. That means much of what is known about TENS and relief of pain comes from studies of devices designed for and applied by healthcare professionals-and there’s no guarantee that over-the-counter versions produce the same results.
What’s more, studies of professional-quality TENS devices have had conflicting results, failing to yield clear answers about the therapy.
Still, some doctors and other healthcare professionals are convinced that there is a role for TENS in treating pain. Some proponents argue that the reason TENS has failed in many studies is that the therapy wasn’t performed correctly. They note that researchers who found no benefit often used devices set at low intensity, which was unable to provide adequate nerve stimulation and trigger the cascade of biochemical changes that block the transmission of pain signals.
What the studies say
TENS is a conservative, nondrug treatment that may help relieve various types of pain, according to some, but not all, studies. A review by the Cochrane Collaboration evaluating TENS for acute pain (such as that resulting from rib fractures or medical procedures) included 19 studies and concluded that there was “tentative evidence” that it could reduce pain intensity compared to a placebo (usually a TENS device delivering little or no current). But it noted that many of the studies were small and had methodological problems, such as inadequate “blinding” with respect to whether the real or sham treatment was being given.
An earlier meta-analysis that pooled data from 38 studies concluded that TENS was effective for chronic musculoskeletal pain, compared to a placebo.
As for chronic low back pain, in particular, a Cochrane review of four studies concluded that the evidence was conflicting, and thus the efficacy of TENS was unclear. However, a large observational study in Orthopedics analyzed data for Medicare patients with chronic low back pain and found that those using TENS required fewer pain-related hospital stays or doctor visits than those not using the devices.
If you decide TENS might be worth a try, keep the following issues in mind before you purchase a device:
- Some research suggests that people who use TENS frequently develop a tolerance to its effects, making the therapy less effective.
- Electrode pads lose their adhesiveness over time and need replacing, adding to the cost.
- While TENS is generally safe and free of side effects, it’s not for everyone. Don’t use TENS devices if you have a pacemaker or any other implanted device made of metal.
- Follow all instructions that come with a TENS device, especially those regarding proper placement; affixing one to certain parts of the body, such as the face or upper back, can cause muscle spasms.
- In rare cases, users have developed skin irritation.
- Medicare reimbursement for TENS devices is very limited-for example, TENS for chronic lower back pain is not covered. You’ll need to find out from Medicare (1-800-MEDICARE) whether a TENS prescription for your particular diagnosis is covered.
It’s always wise to check with your doctor before making any addition to your treatment regimen, so ask him or her if TENS makes sense for you. Additionally, keep your expectation s in check and maintain a proper perspective. TENS might help, but it’s best thought of as an addition to-not a replacement for-exercise, medication, and other well-established back pain aids.