TENS is a therapy that uses low voltage electrical current for pain relief. The machine is connected to the area of pain via electrodes which are placed on the skin. TENS works using the pain gate theory. Put simply, we feel pain when pain receptors in our body are stimulated and a pain signal is sent along certain types of nerve fibres (A-delta and C) to the spinal cord. In the spinal cord the nerve fibres encounter a gate-like mechanism that opens and closes to allow or prevent signals from then travelling on to the brain. If the so-called ‘gate’ is open, the pain signal travels on to the brain, where the pain is registered and so we perceive the pain. It is thought that the electrical current from a TENS