A TENS unit is a small battery-powered device that sends gentle electrical pulses through sticky pads placed on the skin. The tingling sensation can dull pain signals for some people, which makes it a popular drug-free option for back, neck and joint aches after an injury. It does not heal tissue, and it suits some types of pain far better than others, so it works best as one part of a wider recovery plan.
TENS is short for transcutaneous electrical nerve stimulation. "Transcutaneous" simply means "across the skin": nothing is implanted, and the only thing passing between the pads is a mild current.
Two explanations are usually given for why it can help. The first is the gate idea: the buzzing sensation travels along nerves at the same time as pain messages, and the spinal cord gives priority to the new, harmless signal. The second is that certain pulse patterns may prompt the body to release its own pain-relieving chemicals, endorphins. Responses vary a great deal between people. Some notice clear relief, others feel very little, and the effect usually fades soon after the device is switched off.
The general rule is to place the pads around the painful area rather than directly on the sorest spot, with a gap of a few centimetres between them so they never touch. The leaflet that comes with your device, or a physiotherapist, can show positions for your particular problem. Common starting points look like this:
| Area | Typical pad position | Things to watch |
|---|---|---|
| Lower back | Two or four pads either side of the spine, framing the ache | Keep pads off the spine itself |
| Neck and shoulders | On the upper back and the tops of the shoulders, behind the neck | Never on the front or sides of the neck |
| Knee | Above and below the joint, or either side of the kneecap | Avoid surgical wounds and broken skin |
| Shoulder | Front and back of the joint, around the sore point | Stay away from the chest |
Most units let you change the intensity, the pulse rate and the pattern. If you are new to TENS:
Pulse rate and pattern options differ between models, so the manufacturer's instructions are the best guide. A physiotherapist can suggest which programme suits your kind of pain.
TENS is generally considered low risk, but it is not for everyone. Speak to your GP, physiotherapist or the team treating you first if any of these apply:
Do not use TENS while driving, operating machinery, in the bath or shower, or as you drift off to sleep.
Think of TENS as a way to take the edge off pain so that other things become easier: a walk, a set of exercises, or a decent night's sleep. It does not repair a strained muscle or a damaged joint, and using it to push through activity your body is not ready for can set you back. A steady approach is set out in pacing your return to everyday activity after an injury.
It is also not a substitute for a medical check. If pain after a fall or collision is severe, spreading or getting worse, or comes with numbness, weakness or other worrying symptoms, get it assessed before reaching for gadgets. The guide to aches and pains after a car accident lists the signs that need prompt attention.
Many people use one daily, sometimes in several short sessions. The instructions with the device give limits, and it is sensible to take breaks so the skin under the pads can rest.
No. It tends to be tried for muscle and joint aches, back and neck pain and some nerve-related pain, with mixed results. If it has done nothing after a fair trial, it may simply not suit your pain.
Yes, if you are curious. A clinician who knows your injury can say whether it is worth trying and where the pads should sit. Writing the question down beforehand helps it get asked; see questions worth writing down.
Before your next appointment
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