Transcutaneous Electrical Nerve Stimulation (TENS)


Welcome to River East Physiotherapy’s guide to Transcutaneous Electrical Nerve Stimulation.

Electrical nerve stimulation is a treatment for pain that can be used for acute pain (e.g. after knee surgery) or for chronic pain (e.g. persistent low back pain). It sends electrical energy to the nerves. The electrical energy is delivered through electrodes placed on the skin, and it is therefore called "transcutaneous" (through the skin) electrical nerve stimulation, or TENS for short.

TENS is a non-invasive way to reduce pain.  It works by creating a buzzing or tingling sensation that distracts the brain from feeling pain.  In theory, when the the buzzing sensation is sent by nerves from the skin up the spinal cord to the brain, it blocks the sensation that the brain perceives as pain. So you feel the buzzing/tingling, not the pain.

TENS is usually a temporary source of pain relief, but in some cases it can lead to longer-lasting relief. 

In addition to controlling pain, TENS can also improve local circulation and reduce  muscle spasm.

This guide will help you understand:

  • Who may benefit from a TENS unit
  • How a TENS unit works
  • What to expect with a TENS unit
  • Who may benefit from a TENS?

Who May Benefit from a TENS

TENS can be used for relief of pain associated with a wide variety of painful conditions, including:

  • Acute soft tissue injuries (e.g. sprains and strains)
  • Back pain caused by muscle strains, ligament strains, disc injuries, or failed back surgery
  • Nerve pain (neuropathy) from conditions such as chronic regional pain syndrome (CRPS) or diabetes 
  • Cancer-related pain
  • Phantom-limb pain (a chronic pain syndrome following limb amputation)
  • Migraine or tension headaches, when associated with neck muscle conditions.
  • Muscle soreness from overuse,
  • Inflammatory conditions, such as rheumatoid arthritis and osteoarthritis.

Sometimes TENS is used after surgery for incision or post-operative pain (e.g. joint replacement, cardiac procedures, various abdominal surgeries, or cesarean sections). Studies show that TENS can significantly reduce the use of pain medications (including analgesics and narcotic drugs) after surgery.

TENS is usually used along with other forms of treatment and pain control such as analgesics, relaxation therapy, visualization or guided imagery, physiotherapy, exercise, massage therapy, and/or spinal manipulation.

To summarize, the benefits from TENS treatment can include:

  • pain relief
  • increased circulation and healing
  • decreased use of pain relievers or other analgesic drugs
  • increased motion and function

How does a TENS machine work

TENS machines produce an electrical impulse that can be adjusted for pulse, frequency, and intensity.

We know TENS reduces pain, but the exact mechanism by which it works is still unclear.  One theory is that TENS may inhibit (block) pain pathways to the brain, or increase the secretion of the brain's natural pain-reducing substances, such as endorphins and serotonin.  

TENS is a noninvasive way to treat pain. Pain messages may be altered enough to provide temporary or even long-lasting pain relief. Besides controlling pain, this type of electrical stimulation can also improve local circulation and reduce or eliminate muscle spasm.

Recent research has also shown that the placebo effect is a powerful way many people experience pain relief or decrease their symptoms.  This means that by simply believing a treatment works, the nervous system can actually reduce pain. In some cases, this can contribute to the positive effects of using TENS as well.

How do I use my TENS unit

When applied correctly, TENS treatment is a low-risk form of pain relief.

If you have a TENS machine at home, bring it in and your therapist at River East Physiotherapy can show you how to use it.  If your therapist uses one of our clinic's TENS machines, they will apply it for you and teach you what to do when it's on. 

Round or square rubber electrodes are applied to the skin over or around the painful area. The electrodes stick to the skin with gel, which also acts to prevent skin irritation or burning. Usually four electrodes (two pairs) are used to get maximum benefit from this treatment, but two electrodes may be enough.

The TENS unit is battery-operated with controls you manipulate yourself to alter the strength of the electrical signal. The unit can be slipped into a pocket or clipped to your belt.

The electrodes will be placed on your body at positions selected by your physiotherapist. The electrode placement is determined based on the location of the involved nerves and/or the location of your pain. Most often, the electrodes are placed either directly over the painful area or on either side of the pain.

Once the electrodes are in place, the intensity of the unit is turned up until you feel a buzzing, tingling, or thumping sensation.  The sensation should feel strong but still comfortable.

Another way to use TENS is over spots in the muscles called trigger points (TrPs).  Trigger points are areas of hyperirritability in the muscles that can cause chronic pain.  Your physiotherapist will identify any TrPs present during their physical examination.

Significant pain relief may be achieved with as little as 10 minutes of TENS use. Some patients find relief of symptoms for 1-2 hours even after the unit is removed.  Different settings on the TENS machines can increase or decrease the length of time you experience relief, depending on your condition and your tolerance.  

For certain conditions like chronic pain or for women in labour, TENS can be used for several hours at a time.  The unit should not be used, however, for extremely long periods of time (e.g. 24 hours) or during extended sleep time (use during naps is permitted but TENS should not be used while sleeping at night or while sleeping for more than a couple of hours).

If you experience increased pain with a TENS unit, be sure to let your physiotherapist know.  In some cases electrodes placed below the level of a peripheral nerve impairment might actually block the input from the TENS unit and cause increased pain.  Placement over an area of scar tissue from surgery can cause increased skin resistance and decreased transmission of the electrical impulses.

Some guidelines when using TENS

  • Before using TENS for the first time, talk to your therapist to make sure you don't have any "contra-indications".  People with some conditions should not use TENS.  Based on your medical history, your therapist can help make sure TENS is safe for you.  
  • Before applying the electrodes, it is important to remove all lotions, oils, or other applications to the skin. It is beneficial to shave hair from the local area where the electrodes will be applied.
  • We suggest altering the electrode placement slightly each time you put them on, to reduce the risk of skin irritation.
  • The tingling sensation should feel comfortable enough to allow you to complete daily tasks and activities.  It should not be painful.

Consider keeping a daily journal pain levels, the settings used, and a record of the medications being taken for pain relief. By reviewing these notes, you and your therapist can explore the best combination of electrode placement and unit settings that gives you the most pain relief.

What can you expect with TENS

You should feel a mild to moderately strong tingling or buzzing sensation. Depending on your condition and your tolerance, your therapist may also prescribe settings that cause discomfort, such as prickling or twitching. 

After five or ten minutes, the TENS sensation usually becomes less intense and more comfortable - this is because your nervous system gets used to it.  You may have to increase the intensity on the TENS machine over the course of the treatment, so you continue to feel the desired effect.  

Depending on the intensity and duration of your pain, you may not get immediate results.  It can take several days, or even several weeks, to get the desired results. Differences in results may occur based on properties of skin resistance, type of pain, and individual differences in the mechanism of pain control.  When using the TENS be persistent and patient and discuss any concerns you have with your therapist.

Many patients report good-to-excellent results with pain control, pain relief, and a reduction in the use of medications. Although it's rare, some patients with persistent pain can feel “cured” permanently from their pain.

If for any reason your pain starts to increase in frequency, duration, or intensity, don’t assume the treatment isn’t working for you. First, check the TENS unit for any malfunction, the need to recharge the batteries, or the need to replace the electrodes with new ones. If your unit is battery-operated, you may find it necessary to turn the intensity up to obtain the same sensation when the batteries are low. This should alert you to the need for battery replacement.

Finally, be aware that some patients experience “breakthrough pain,” referring to a situation in which you get pain relief at first with the TENS unit but then for some reason even with the TENS unit on you again start to experience pain.  Needing to turn the intensity up high enough to cause muscle contraction is an indication of breakthrough pain.

Sometimes a different setting for the stimulator may be needed when breakthrough pain occurs. Most units have a setting that allows for random pulse frequency, duration, and amplitude. This setting helps keep the nervous system from adapting/habituating to a specific amount of stimulation.

Contraindications: When you should NOT use TENS

  • Never place an electrode over an open wound or area of skin irritation. Report any skin problems or burns immediately to your therapist.
  • Do not place electrodes near your eyes, on your head, or on the front of your neck.
  • Do not use TENS in the shower or bathtub.
  • If you are having reduced feeling in your skin, or are experiencing unusual skin sensations. If you can't feel the TENS signals properly, there is a risk of turning the intensity up too high and causing an injury.
  • If you have a cardiac pacemaker as the electrical signals could interfere with the pacemaker. In general, people with cardiac conditions should not use TENS without their physician’s approval.
  • If you are pregnant, do not use TENS near or on your abdomen or lower back.
  • Do not use TENS if you have Alzheimer’s Disease, dementia, or other cognitive problems, unless your doctor or therapist has confirmed it's okay.
  • As for other contraindicated medical conditions, TENS should not be applied: over a deep vein thrombosis, near an infected lesion, over recently radiated tissue, over reproductive organs, over regenerating nerves, in an area with malignant cancer, or to people with bleeding or hemorrhagic disorders.


TENS can be an excellent, low-risk, drug-free approach to pain relief.  When used as part of a physiotherapy or athletic therapy treatment plan, it can be a great treatment for many of the conditions we treat at River East Physiotherapy & Sports Fitness Clinics.  

As always, work closely with your therapist to customize your TENS treatment to your unique medical history and your condition.  

Still not sure whether TENS is right for you?  Call us for a free 15-minute phone consultation with a physiotherapist.

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