Detection volume of simulated electrode systems for recording sphincter muscle electromyogram

The detection volume of EMG recording systems from sphincter muscles extends more in the axial than in the depth direction and is affected by many parameters that cannot be estimated in practical situations, thus introducing a rather large variability in the muscle portion investigated among subjects. More selective information can be obtained using the recently developed multi-channel probe with respect to classical probes. Selectivity is increased with small electrodes and double differential recordings.