*3.2.1. Surface electrodes*

Surface EMG electrodes are placed on the skin overlying a muscle. It is typical for surface EMG signals to be detected using a bipolar electrode configuration consisting of two electrodes with surface areas approximately equivalent to that of a 1 cm by 3 cm rectangle and with approxi‐ mately 1 cm spacing. However, surface electrode arrays with more than 2 electrodes, smaller detection surfaces and electrode spacing have been developed. Huppertz et al. used two columns of electrodes [7] to detect surface EMG. In [13], a 2-dimensional array of electrodes, which consisted of 128 electrodes in total, was used.
