Electrical concepts in the surface electromyographic signal.

There are frequently used electrical terms in the biofeedback literature. Often it is assumed that the reader has detailed knowledge of these terms. The difficulty begins when seemingly familiar terms are used as a basis for an in-depth explanation of the process of electromyography. For example, the concept of impedance is based on three building blocks of electricity: current, voltage and resistance. The term "impedance" is found in every manual for biofeedback equipment with the suggestion that the electrode site be kept "low" and the encoder input "high". A little electrical knowledge can explain why this is so and in the process formulate a more thorough understanding of the equipment used everyday with a client.