Transcutaneous electrical nerve stimulation (TENS) devices have been around since the 1960s and help with pain management by delivering electrical impulses across the skin.

Does it work for everybody?

For some people, using a TENS machine leads to some degree of pain relief. For others, the sensation just takes their mind off the pain for a while. Unfortunately, for some people it is not helpful or they find the sensation too unpleasant.

TENS machines are usually a small with wires leading to self-adhesive pads, although wearable belts suitable for back pain are also available.

The pads are placed on either side of, on top of, or close to the painful area. When switched on you get a tingling sensation under the pads. Aim for a strong, but comfortable, sensation. The right sensation for you can be found using the controls on the TENS machine.

There are several units on the market – these can be purchased in pharmacies, larger supermarkets and online. We recommend the TPN 200 (plus) unit which can be purchased from many different internet suppliers and costs around £25. It has low operating costs and tends to be very reliable and relatively easy to use.

How does it work?

Research shows the TENS machine operates through the pain gate, the special system which helps to block pain messages going up the spinal cord.

Other evidence suggests the TENS machine also stimulates some of the opioid systems, or natural pain-killing systems, within the body.

The third mechanism is the distraction mechanism. It may actually just take your mind off the pain.

All of these mechanisms may help to alter the pain you are experiencing.

Who can use a TENS machine?

TENS can be used for all pain conditions, providing there is no health reason preventing its use. However, it can be difficult if you have many pain sites, especially if the pain can move and vary during the day, so you end up chasing the pain with the TENS machine.

People with widespread pain, such as fibromyalgia syndrome, may feel it is difficult to choose a specific area to treat but it may be possible to select one treatment area such as the lower back, to see if the TENS machine can offer an overall benefit.

People with widespread pain often have a localised pain problem which can be helped through using a TENS machine, even if it doesn’t help their more widespread pain.

It is down to each individual to try out different approaches to see what may help them.

TENS is not safe for everyone to use

You should not use TENS if you:

• have epilepsy
• have a pacemaker or other implanted electronic device fitted
• are pregnant (except for pain relief during labour)
• are a child
• have a recent history of bleeding, blood clots or very poor circulation
• are unable to feel the sensations from the TENS machine.

If you are unsure, speak to your healthcare professional.

Different strategies for using TENS

From research with people living with chronic pain, there are five main strategies which seem to allow individuals to gain the most benefit from their TENS machine:

1. For particular activities, such as walking or sitting, which would otherwise have been difficult because of pain.
2. Intermittently during the day, during a rest break, perhaps in combination with relaxation techniques.
3. On a bad day only or during a flare-up to help cope and get through the pain.
4. On and off all day to help with most daily activities.
5. In the morning, to help with the extra pain and stiffness that some people experience first thing.

Using a TENS unit

The TENS machine requires a standard or rechargeable nine-volt battery. The dials on the machine turn the machine on and off and increase the intensity of a TPN 200 TENS machine. Always make sure the machine is switched off before starting.

• Make sure the selected skin area is clean, dry and the skin is not broken or numb. You should also refrain from using any body lotions, creams or talc on the area.
• Connect the pads to the pins on the lead wire and position pads onto the skin area, leaving at least four fingers width in between the pads.
• Making sure the unit remains switched off, connect the lead wire to the TENS device.
• Switch the TENS machine on using the dial immediately next to the lead wire.
• Gradually increase the intensity by turning the dial in a clockwise direction until you first experience a ‘tingling’ sensation.
• Slowly increase the intensity until the sensation felt is firm but comfortable.
• The sensation felt should always be strong, but comfortable. The intensity should not be painful or cause muscle contraction.
• After a few minutes, the sensation will start to drop slightly – this is called accommodation. When this happens, turn the machine up slightly.
• Do not turn the unit’s sensation too high or strong, as it can cause over-stimulation, which may make your pain worse.
• At the end of the session, turn the machine off. You can disconnect the electrodes from the unit if you wish, or keep it all in place for use later. There is no need to remove the pads if you intend to use the TENS machine again later. Simply tuck the wires out of the way and carry on as normal.
• Once you have finished using the TENS for the day, turn the machine off before removing the pads from your body, placing the pads back on the plastic sheet and sealing them into the bag they came with.
• Do not allow any part of the machine to get wet, apart from the pads if they have stopped sticking properly.
• Do not use the TENS machine if you are driving or operating heavy machinery.

Controls will vary based on the unit you purchase, however, the following are some general settings.

• Mode: Refers to the type of stimulation you will feel when the unit is on and the pads attached to your body.
• B: Burst.
• C: Continuous.
• M: Modulated or wave-like.
• Pulse width: Shorter pulse durations are generally more comfortable and do not provoke muscle contraction or 'twitching'.
• Pulse rate: High frequency → 80-130Hz – stimulates the pain gate = short term. Low frequency → 2-5Hz – stimulates the opioid mechanism = longer term.

Using the electrode pads

The electrode pads are self-adhesive and should last for about 30 applications if reapplied to the plastic sheet between each use and sealed in the bag they came in.

Their life span can vary depending on the individual’s skin resistance and the length of time or frequency of application.

A useful tip to renew ‘stickiness’ of the electrodes is to wipe the sticky side of the pads with a damp finger under running water, reapply to the plastic sheet and put them in a fridge for a few hours.

Please remember not to use cream and powder under the electrodes. Replacement pads can be purchased through the unit’s manufacturer or online.

Positioning the pads

There are places which you should not place the pads. Never place the pads over:

• the front or sides of your neck
• your temples
• your mouth or eyes
• your chest and upper back at the same time
• irritated, infected or broken skin
• varicose veins
• numb areas.

In general, try to surround the pain, placing the pads near the pain and just above it if possible.

If this is not comfortable or possible, you can put the pads either side of the spine at the correct dermatome. The dermatome level is the level of the spine where the nerves from your painful part pass into the spine.

For example, if you have pain in your arm you could place the pads on the low part of the neck either side of the spine.

If you have pain in the front of your knee, you could place the pads just below your waist, either side of the spine. If you have sciatica you could place the pads low down on your back, just above your buttocks, either side of the spine.

Hints and tips

• The preferred type of sensation is personal. Some people prefer a stronger intensity, and others prefer it less strong. You should not use it at a setting which is painful or causes the muscles to twitch or contract.
• The settings on most machines can be adjusted to suit individual preferences and can be changed to give a different sensation you may prefer.
• Despite being hypoallergenic, the pads can aggravate very sensitive skin. Rubber pads with gel are an alternative which can be less irritant. If you get skin irritation, some people find the use of over-the-counter hydrocortisone cream can help manage this. You should not use TENS on areas of broken or irritated skin.
• Be persistent, don’t give up if you don’t get immediate benefit – try changing the settings, pad placement or when you use the unit.
• TENS works particularly well on pain you can predict will get worse, such as when doing a certain activity. Turning it on before you do the activity, keeping it on while undertaking the activity and for a while after finishing the activity is often a good way to use TENS.
• Alternatively, if your pain is always worse at a specific time, using it during this time can be beneficial, for example, last thing at night or first thing in the morning.
• TENS is less likely to help if you wait until the pain is worse before you start to use it.