Technical Aspects of Surface Electromyography for Clinicians

Surface electromyography (sEMG) is a measure of the electrical potential present on the skin in consequence of a muscle contraction. This voltage is detected by electrodes placed on the skin. Under certain limitations, when a proper protocol for electrode placement is used, the voltage measured on the skin can be related to the activity of a single specific muscle. The signal is represented as a trace that develops during time, increasing from zero up to tenths or hundreds of microvolts as the muscle becomes activated. Being a non invasive and painless measure, sEMG has been applied in motion analysis to assess superficial muscle function, with application in sports, ergonomics, occupational and rehabilitation medicine. It allows for investigation of both muscle activation and muscle physiological characteristics. The first part of this work provides an overview on sEMG signal acquisition technique and its representation, focusing on those elements that ensure signal reliability and on the sources of errors and artifacts. The second part of this work provides a critical overview on the information that can be extracted from the sEMG signal, dealing with amplitude, timing and morphology.