The application of electricity to needles was a Chinese innovation. It is usually done by attaching crocodile clips to the needles; obviously at least two needles must be inserted, unless a neutral electrode is used. Often several pairs of needles are inserted. Direct current is unsuitable because it causes an electrochemical effect which weakens the needles and ultimate causes them to break. A pulsed wave of some type is therefore used. The frequency may be slow (2 to 10 Hz) or fast (80 Hz or more).
These two types of stimulation are said to give rise to different patterns of endogenous opioid secretion. Originally electrical stimulation was mainly used for producing acupuncture analgesia, when it was necessary to give continuous stimulation for long periods; it was later applied to treatment of disease. Initially there was a lot of enthusiasm for electrical stimulation among Western acupuncturists but this seems to have diminished in recent years. In my experience electricity does not seem to add anything useful to manual stimulation, and clearly it has no place in the brief needling techniques which I describe here. I now use electrical stimulation only in very rare cases.