TENS - transcutaneous electrical nerve stimulation
TENS stands for transcutaneous (through the skin) electrical nerve stimulation. It is a treatment that uses low voltage electrical currents to help relieve pain. The gentle current comes from a small battery-operated machine, and passes through wires to electrode pads that are attached to the skin near the site of the pain.
TENS can be used to help treat many painful conditions. And because TENS machines are portable and easy to use, people can use them at home and while they are going about their daily activities.
What types of pain do people use TENS for?
TENS is used by people to treat a variety of painful conditions, including:
- low back pain;
- rheumatoid arthritis;
- tennis elbow and other sporting injuries;
- neck pain;
- knee pain;
- period pain;
- neuropathic pain (pain caused by nerve or spinal cord damage);
- cancer pain; and
- the pain of childbirth.
TENS can be used to treat both short-term (acute) and longer-term (chronic) pain.
What does TENS feel like?
You will feel a tingling or buzzing feeling on your skin where the electrodes are placed. Some people may find this sensation unpleasant.
How does TENS relieve pain?
It is not exactly certain how TENS relieves pain. One suggestion involves the 'gate control' theory of pain (see below). It’s also thought that TENS helps relax muscles, as well as stimulating the release of endorphins - the body’s own natural painkilling substances.
Gate control theory of pain
To help understand the gate control theory of pain, try thinking of the spinal cord as having a gate-like mechanism that controls and prioritises which messages reach the brain. When the gate is open, pain signals can travel through the spinal cord to the brain, where the signal is registered and perceived as pain. But when the gate is closed, pain signals do not reach the brain, so pain is not registered.
But what can close the gate? The gate can be closed by non-pain sensory signals carried by large nerve fibres. This means that touch signals reaching the spinal cord can close the gate on the pain signals and block them. So the pain signals will not be able to reach the brain to be perceived as pain.
An example of the gate control theory in action is when we hurt ourselves and rub the painful area. The signal from the sensation of touch (rubbing) can temporarily block the pain signal travelling from the injury to the brain, making you feel better.
The gate control theory is also thought to be involved when using a TENS machine. The electrical current stimulates nerve fibres that carry signals relating to touch. The signals travel to the spinal cord where they temporarily block the transmission of pain sensations to the brain. By closing the gate, you can help relieve or reduce pain.
How effective is TENS at relieving pain?
Many people find that TENS effectively relieves their chronic (ongoing) pain and there is some evidence that TENS can help reduce the intensity of acute pain (pain of recent onset and short duration) in adults. However, the overall published evidence supporting its effectiveness is not so clear. In general, not enough good studies have been done to draw firm conclusions. Some people find that TENS does not help their pain at all.
But despite the lack of evidence, there is little downside in trying TENS for pain relief in many situations because it is a safe and inexpensive treatment option. TENS can be used either on its own or together with other treatments.
In general, TENS is most beneficial when started under the supervision of a trained therapist. Some people find that they only get pain relief while the TENS unit is operating; for others the pain relief continues after they’ve stopped their TENS treatment.
How to use a TENS machine
Check with your doctor if you are thinking of using TENS. Your GP (general practitioner) can refer you to a pain clinic or to a physiotherapist for treatment with TENS.
It’s important that you start treatment with a trained healthcare professional so that you get the most benefit. This person can show you how to use the machine yourself, the best place to apply the electrode pads and the best settings for you.
TENS machines are small and lightweight, so if you want to you can attach it to your belt or put in your pocket and receive treatment while you are going about your day. It may actually even help reduce pain enough so that you are able to do your activities more easily. Just don’t use your TENS machine while you are driving, or when in the bath or shower.
Placing the electrode pads
Most TENS machines come with 2 or 4 electrodes. The electrode pads should generally be placed around the area that is painful. However, you should NOT place TENS electrodes on:
- the front or side of your neck;
- anywhere on your face;
- the chest and upper back at the same time;
- over an area of broken skin; or
- over varicose veins.
Which settings should I use?
TENS machines usually have an adjustment for the intensity and also the frequency (high/low) of the electrical current. It’s best to start on a low setting and gradually increase it. The tingling sensation should feel strong but comfortable - it should not be so strong that it hurts.
High-frequency TENS is thought to be best for blocking pain signals, while low-frequency TENS is said to be more effective for stimulating the release of endorphins.
How often or for how long can I use the TENS machine?
Your doctor or physiotherapist will be able to advise you on how long and how frequently TENS should be used. This may vary according to why you are using it, the type of machine you have and the recommended settings. If you are using your own TENS machine, make sure that you carefully read the instructions and recommendations beforehand.
When starting to use a TENS machine at home, many people start off using the device for up to an hour a few times a day. This may be increased to longer periods of time in some people.
Can anyone use a TENS machine?
The short answer is no – TENS is not suitable for everyone. Before using TENS, make sure you ask your doctor if it would be an appropriate treatment for you.
You should NOT use TENS if you have:
- a pacemaker or implanted cardioverter defibrillator (ICD);
- a cochlear implant hearing device;
- any other type of implant in your body; or
- a severe heart disorder.
You should also not use TENS if you are pregnant or think you might be pregnant. And don’t use it while you are alone if you have epilepsy.
Are there any side effects from using TENS?
TENS appears to be free of any side effects except for occasional skin irritation where the electrodes are applied. Special electrode pads are available for people who have a skin reaction to the regular pads.
Some people may find the sensation of TENS too unpleasant to be able to use the machines.
Where can I get a TENS machine?
You may be able to borrow or hire a TENS machine from your physiotherapist or pain clinic. TENS machines are also sometimes available for loan or hire from hospitals and pharmacies.
You can also buy your own machine for long-term use if you’ve found it helps relieve your pain. TENS machines can be bought direct from manufacturers via the internet, from medical equipment suppliers and from some pharmacies. Some health funds may rebate some or all of the cost of the machine.
Although you can buy a TENS machine direct from a manufacturer or distributor, ideally it should be demonstrated by a trained healthcare professional so that you get the most benefit.
PENS (percutaneous electrical nerve stimulation)
PENS is a similar therapy to TENS, but, with PENS, the electrical stimulation is passed through the skin into the soft tissue using needle probes similar to acupuncture needles.
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