What is TENS?
Transcutaneous Electrical Nerve Stimulation (TENS) is a mouthful to say! 
Transcutaneous is a medical term & simply means through the skin. TENS is passing small currents through your skin to the nerves below to reduce or abolish your pain. It doesn’t cure your pain problem but reduces it. The current is passed through 2 sticky electrodes (also called pads) which you place over the painful area and join to the TENS machine. There is an enormous range of painful conditions helped by TENS. From acute pain such as sports injuries, whiplash, migraine, period pains and tension headaches to chronic pain such as arthritis, backache, sciatica and fibromyalgia.
The small currents stimulate (or excite) nerves which in a clever and slightly complicated fashion both calm the pain nerve fibres directly, stop the pain messages reaching the brain, help your body produce it’s own pain killers and stimulate various anti-inflammatory substances which encourage your body’s healing processes. All from a small machine and some sticky pads. For more details please look at - how does TENS work
There are different types of TENS and most machines will do all of them. Briefly they are conventional TENS, ‘acupuncture like’ TENS and modulated TENS which varies the settings automatically.
Conventional TENS uses high frequencies (more than 60 pulses per second) and feels like a buzzing or tingling sensation.
‘Acupuncture like’ TENS uses low frequencies (from 1 to 20 pulses per second) and feels like someone’s gently tapping you.
Modulated TENS varies the frequency and pulse width over a few seconds so it feels like someone’s massaging you. Very soothing!
Modern machines usually have pre set programmes meaning you don’t need to worry over setting up the machine and what words like frequency, pulse width and current mean. Just pick the programme and start.
To use a TENS machine the electrodes are usually placed over your painful area to begin with. The current (also called the intensity) is slowly increased until you feel a mild tingling sensation. It’s just like turning up the volume on the television. Starts off silent, then you hear it fine but go too high and your ears hurt! You don’t need very high currents for TENS to work. It shouldn’t feel uncomfortable, if it does reduce the current a bit. Leave it going for 20 – 30 mins and finish. That will give you pain relief for up to 10 – 12 hours.
There is a huge amount of evidence that TENS works and it is widely used in hospitals, delivery suites and labour wards, pain clinics and surgeries. It is safe, easy to use, doesn’t interfere with any drugs you are taking and has few side effects.