A TENS unit is a device that stimulates nerves throughout the body by applying an electrical current through the skin. People use it to reduce chronic pain, prevent headaches and migraines, and improve mood. Read on to learn what else they might do.
What is TENS?
Figure 1 Source: http://www.therxreview.com/tens-unit-what-it-is-and-what-it-does/
TENS is short for transcutaneous electrical nerve stimulation. It is generally considered a safe (when used correctly), inexpensive, and non-invasive method of stimulating nerves by applying electricity to the surface of the skin.
For more about TENS and how it might work, check out this post.
TENS units have not been approved by the FDA for any medical purpose or health claim. Talk to your doctor before using TENS.
TENS devices are classified as Class II devices. They can be approved as “adjunct in the treatment of pain” as long as they are similar enough–that is, at last as safe and effective–to already cleared TENS devices on the market.
Uses of the TENS unit
Insufficient Evidence for:
No valid clinical evidence supports the use of TENS for any of the conditions listed in this section.
Below is a summary of the existing clinical, animal, and cell-based research that should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
According to a recent Cochrane overview of reviews, it is not possible to confidently state whether TENS is effective in relieving pain compared to sham TENS, usual care/no treatment, or combined with another active treatment versus the active treatment alone .
Shoulder & Back Pain
In one study, the TENS unit reduced shoulder pain and improved shoulder joint mobility of 90 participants with shoulder pain from paralysis on one side of the body (hemiplegia). TENS also improved their overall quality of life .
Insufficient evidence suggests that the TENS unit may help people suffering from chronic pain. In a small observational study of 33 people with chronic back pain, 14 (42%) of them experienced at least a 30% pain reduction from TENS. And out of the 14, 13 felt the benefits within an hour or less of using the TENS unit. This study had many limitations .
A study of 60 patients with upper back pain found that using a TENS unit reduced pain better than placebo .
In another study of patients with back pain, those who used TENS ended up making fewer hospital and clinic visits .
A study in arthritis patients found that using a TENS unit helped reduce pain during walking and at rest .
Similarly, there is insufficient evidence to say that the TENS unit helps with pain related to dental procedures. Using the TENS unit in preparation for cavity-filling treatments suppressed pain during the procedure in 80% of patients in one study .
Pain After Surgery
A study with 54 patients that underwent spinal surgery found that TENS had a pain-reducing effect (analgesia). It reduced the number of needed painkillers and their side effects .
Patients who used a TENS machine after surgery required less pain-relieving medication in another large study of 1,350 people .
Those who used a TENS unit after surgery had lower levels of pain than those in the control group in a study of 40 patients who underwent surgery that required a large chest incision (a procedure called posterolateral thoracotomy, often used for lung or heart surgery) .
In a study with 40 patients who underwent open-heart surgery, using the TENS unit at acupuncture points (“Acu-TENS”) helped to return blood pressure and heart rate to normal more quickly and using fewer medications (compared to patients who did not use TENS) .
Both high- and low-intensity TENS treatment helped relieve pain following major surgery in another study of 64 patients .
Patients who used TENS after surgery had improved breathing, less pain, and required less pain-killing drugs than patients who did not use TENS in a study with 50 patients who underwent chest surgery. A related study concluded that using a TENS unit alongside painkillers may relieve pain better than just the medication [13, 14].
However, not all studies have found a beneficial effect on pain after surgery.
For example, in one study with 45 patients who received surgery (pulmonary artery bypass), using TENS did not significantly reduce pain .
According to some, small differences in TENS procedures might make a big difference in terms of its effectiveness and health benefits. However, no evidence backs up such claims.
In fact, a recent Cochrane overview of reviews didn’t find any reliable evidence that the effectiveness of TENS varies when using different delivery modes (e.g. different frequency, intensity or electrode placement) .
A study with 110 patients found that applying TENS at the base of the head (occipital nerve) decreased the duration of headaches in migraine sufferers. It also had low rates of side effects, making it a possible option for to patients that did not want to take medications for their migraines .
Similarly, a study in 57 patients found that using a TENS unit reduced both the number and intensity of pain episodes in a headache and migraine sufferers .
Another study found that the use of TENS for headaches decreased medication use and helped patients manage their chronic migraine symptoms better .
Finally, another study in migraine patients reported that TENS treatment reduced the total amount of days with a headache. 66% of the patients in this study decided to continue using a TENS unit to keep their headaches at bay, although the patients who followed the TENS directions the best reported the greatest benefits at a follow-up .
A technique called Transcutaneous Vagus Nerve Stimulation — or “tVNS” for short — is a method of using TENS to stimulate the vagus nerve (which is done by hooking the TENS unit up to specific parts of the ear).
This TENS technique has shown some promising early data on helping with psychological disorders such as depression. Limited studies have found that tVNS may reduce symptoms of depression — for example, by stimulating the regions of the brain associated with reward processing and motivation — and leads to improvements in depression patients’ overall level of symptoms. However, proper clinical trials are still lacking [20, 21, 22, 23, 24, 25, 26].
4) Stroke Recovery
Strokes often cause extensive damage throughout the brain, which can cause a lot of long-term after-effects that can be very difficult to recover from. Many stroke patients end up having difficulties moving and walking, although insufficient evidence shows that TENS treatment may help stroke victims recover from these impairments.
A study in 14 chronic stroke patients found that pairing TENS treatment with exercise improved their balance and enhanced their ability to walk and that these improvements were greater than those from just exercise alone .
Similar results were found in another study with 34 stroke patients. Pairing TENS with exercise training over 6 weeks led to improved balance, walking ability (gait), and reduced muscle stiffness and spasms .
TENS also increased the effectiveness of exercise in stroke sufferers by increasing their walking speed and walking distance in a study of 109 patients .
Another study with 14 stroke patients reported that TENS treatment helped improve their ability to walk and control the lower halves of their body .
5) Menstrual Cramps and Labor Pains
There is insufficient evidence to suggest that TENS units reduce menstrual cramps and labor pains.
A study with 40 women who had very painful menstrual cramps (dysmenorrhea) found that TENS was effective at reducing cramp-related pain, and led to improvements in these patients’ quality of life. The patients used a portable TENS units, which was particularly helpful in maintaining their treatment effectively .
In another study with 134 women with painful menstrual cramps, TENS reduced both the intensity and duration of pain more than a placebo treatment .
TENS was also useful for quickly relieving menstrual pain in a study with 40 women. Three months after the study, 70% of the women were still using the TENS unit regularly with no adverse side effects .
The TENS unit may relieve pain associated with giving birth. A study found that women who used a TENS unit during their stay at the hospital experienced less labor pain, suggesting that TENS may be helpful both during and after labor .
6) Symptoms of Parkinson’s Disease
There is insufficient evidence to suggest that TENS units reduce Parkinson’s disease symptoms.
People with Parkinson’s disease often have uncontrollable shaking (motor tremors). Two studies suggested that using TENS on the hands and arms of Parkinson’s patients can help suppress their uncontrollable shaking by an average of 62% [33, 34].
Another common symptom of Parkinson’s is difficulty walking (“freezing of gait”). A study found that applying TENS to the feet and legs of Parkinson’s patients improved the ability to walk in 12% of the patients tested, and increased the amount of time that these patients could walk by an average of about 20% .
Large-scale studies are lacking.
7) Urinary Incontinence (Bed-Wetting)
There is insufficient evidence that TENS units improve urinary incontinence.
In one study, 42 patients with overactive bladder syndrome (OBS) got a TENS unit and also kept a “bladder diary” for 48 hours to keep track of their symptoms. TENS was safe and effective for OBS, with 50% of the patients reporting that they were “satisfied” or “very satisfied” with the treatment. The TENS unit also resolved uncontrolled urination (urinary incontinence) in 39% of the patients .
In another study on 47 children around age with bed-wetting problems, applying the TENS unit for one hour twice daily for 10 weeks did not reduce the number of bed-wetting episodes. However, another study found that 72% of the patients had a reduction of at least 1 bed-wetting night per week, which was maintained even after the study [37, 38].
8) Symptoms of Fibromyalgia
A study with 28 fibromyalgia patients found that TENS treatment reduced pain, anxiety, fatigue, and muscle stiffness, which in turn greatly improved these patients’ ability to work .
Another study with 39 fibromyalgia patients has similar findings — TENS treatment decreased pain and fatigue. The authors suggested that using two TENS units together may increase these effects further [40, 41].
However, a review (of 8 fibromyalgia studies) came to the conclusion that there is not yet sufficient evidence to say for sure that TENS consistently works to relieve pain in fibromyalgia patients .
9) Lung Function
In a study with 50 patients with chronic obstructive pulmonary disease (COPD), TENS treatment increased the amount of air the lungs can hold (lung capacity) and improved the overall symptoms .
In another study in 21 COPD patients, the TENS improved breathing during exercise, although it did not increase in the amount of time they could walk .
A couple of other small-scale studies have reported similar effects — improved breathing in COPD patients during physical exertion — with both TENS and “Acu-TENS” (a technique of using TENS stimulation at acupuncture points on the body) [44, 45, 46].
10) Voice Quality
In a study with 4o women, those who used the TENS unit had an increase in their voice quality and intensity, which made them feel more comfortable while speaking. A review of studies confirmed that the TENS unit might improve voice quality, while pointing out that large-scale studies are needed [47, 48].
The TENS unit also improved the symptoms of behavioral dysphonia, a type of speech impairment without an unknown cause. In a study in 30 women, TENS improved their voices and reduced speech impairment .
11) Sensation in Prosthetic Limbs
When a person loses one of their limbs, they will sometimes continue to experience feelings in the parts of their body that are no longer there — a condition known as a “phantom limb”. Researchers began to search for ways to re-create the sensation of lost body parts. They applied TENS to the amputated body to develop advanced robotic replacements (prosthetic limbs) that could feel real. Although still in the early stages, this could be a huge leap forward in the technology of robotic prosthetics and body-machine interfaces .
Possibly Ineffective for:
In one of the relatively few studies to use a realistic “placebo” condition, 13 healthy young men were given either real or fake (“sham”) TENS treatment. The real TENS improved resting heart rates and led to better regulation of blood pressure. During fake TENS, the participants are hooked up to a real TENS machine but receive no actual electrical current — particularly important for teasing apart the actual TENS effects .
However, the cardiovascular benefits of TENS likely don’t apply to everyone, but only to people who are already healthy. For example, in a study of 45 patients, using a TENS unit after heart surgery (pulmonary artery bypass) did not reduce their future risk of heart problems .
Some older studies reported that TENS helped reduce high blood pressure. However, a more recent study with 32 hypertensive patients found no evidence that the TENS unit decreases blood pressure .
A study found that using a TENS unit while stretching increases athletes’ range of motion and reduces muscle pain .
Another study also found that TENS increased the amount of time that athletes could exercise (increased endurance) as well as decreased pain during exercise .
However, another study with 13 participants who used TENS to treat their cycling-related pain found that TENS did not significantly change the amount of pain that they felt, and did not affect the amount of time it took to complete a 5km bike ride .
- What is a TENS Unit? + How to Use & How Does It Work
A TENS unit is a device that stimulates nerves throughout the body by applying an electrical current through the skin. It is most commonly used to relieve pain, though the evidence of any benefit is of relatively low quality due to a lack of well-controlled studies.
Clinical research is under way for many of the purported benefits of TENS units, including migraines, stroke recovery, menstrual cramps, Parkinson’s disease, incontinence, and fibromyalgia. There is currently no strong evidence for any of these benefits.