A TENS machine is one of those purchases that sits in a drawer for six months and then, during one bad week, earns its keep. The kit is simple enough: a small battery-powered unit, two leads and four sticky pads. What's less obvious is where those pads should go, what the buttons actually do, and how to tell whether it's helping or just buzzing. Here's the practical version.
What a TENS machine actually does
TENS stands for transcutaneous electrical nerve stimulation. The unit sends small pulses of electricity through the skin via the pads. The usual explanation is that these pulses travel along nerve fibres and crowd out pain signals before they reach the brain — the "gate" theory. Some settings may also encourage the release of the body's own pain-relieving chemicals, which is why low-frequency programmes often feel quite different from high-frequency ones.
Be realistic about what that means. The evidence for TENS in back pain is mixed, and UK guidance does not recommend it as a routine treatment for low back pain. It won't fix a disc, a joint or a weak muscle. What it can do is take the edge off for a while, so you can move, work or sleep more comfortably. Some people notice a clear benefit; others notice nothing. A two-week trial tells you which group you're in, and there's no harm in stopping if it isn't working.
Safety first: who should not use one
TENS is low-risk for most healthy adults, but it isn't suitable for everyone. Check your device's manual, and speak to a GP, pharmacist or physiotherapist if any of the following apply.
- A pacemaker or any implanted electronic device — including defibrillators, neurostimulators and some insulin pumps. Don't use TENS without clearance from the team that manages your device.
- Pregnancy — avoid placing pads on your abdomen or lower back without advice from your midwife or doctor.
- Epilepsy or a heart rhythm problem — get medical advice before your first session.
- Reduced sensation — for example, peripheral neuropathy or a numb patch of skin. You may not feel the current becoming too strong.
- Anyone who can't say "that's too much" — such as a person with dementia. Don't leave them unsupervised with a unit running.
Never use TENS on broken, cut, infected or irritated skin, over varicose veins, or on the front of the neck, temples, eyes or mouth. Don't arrange the pads so the current crosses your heart. And don't use it in the bath, in the shower, or in bed if you might fall asleep with it on.
Some back pain needs a clinician rather than a gadget. Seek urgent medical advice if you develop numbness around the genitals or back passage, difficulty controlling your bladder or bowels, weakness in both legs, a fever alongside back pain, unexplained weight loss, or pain that wakes you night after night.
Where to put the pads
The aim is to place the pads around the painful area so the current passes through it. For most lower back pain, that means a square or rectangle: two pads on one side of the spine and two on the other, roughly at the level of the ache and just below it.
- Wash and dry the skin. Skip the moisturiser, oil or fake tan — anything greasy stops the pads sticking and can make the current sting.
- Trim thick hair if it's getting in the way. Avoid shaving on the day, as fresh nicks plus electricity is unpleasant.
- Position the first pair either side of the spine, about two to four fingers' width from the midline, at the level of the pain. Put the second pair slightly above or below to bracket the sore spot.
- Press each pad down firmly for a few seconds, paying attention to the corners.
- Connect the leads, switch on at zero, then increase slowly.
- If the tingling is in the wrong place, switch off and move the pads before trying again.
Keep pads a few centimetres apart and never let two touch. Avoid placing them directly over the bony bumps of the spine, over scars or bruises, or across a joint you're about to bend repeatedly. If your pain moves or spreads, reposition rather than turning the intensity up.
Choosing your settings
Most units have two main numbers to play with: frequency, measured in hertz (Hz), and pulse width, measured in microseconds. You don't need to understand the electronics — just which feel suits which situation.
- Conventional (high frequency, roughly 80–120 Hz): a fine, fast tingling. This is the setting most people use during the day, while walking, working or doing exercises.
- Low frequency (roughly 2–10 Hz): a slower, rhythmic tapping, sometimes with visible muscle twitching. Some people prefer it for deep, achy pain, but sessions are usually shorter.
- Burst or modulation modes: the machine alternates between
Photo: Pezibear / Pixabay
