Q: I have chronic lower back pain and my doctor wants me to go for TENS. What is that and how does it work?

A: TENS stands for transcutaneous electrical nerve stimulation. TENS uses electrical impulses, applied to the skin around the area where the pain is located. The electrical currents stimulate the nerves but researchers aren't quite sure how it relieves the pain.

Two theories are that the electrical stimulation of the nerves blocks the sensation of pain sensation or that the stimulation triggers the release of endorphins, the body's natural painkillers.

Small electrodes are place over the area where the pain is and the machine is turned on. As the nerves are stimulated, you should feel a tingling feeling. Your doctor or the Physical Therapist will determine how long the treatment should take place.

Jan Oosterhof, et al. Predicting Outcome of TENS in chronic pain: A prospective, randomized, placebo controlled trial. In Pain. May 2008. Vol. 136. No. 1-2. Pp. 11-20