This contribution analyses the anatomy and neurophysiology of the pelvic floor muscles as well as the multichannel electromyogram (EMG) of the anal sphincter, urethral sphincter and puborectalis muscles. Cylindrical probes carrying one or more circumferential arrays of electrodes are used to detect the generation (at the end-plates), propagation (along the muscle fibers) and extinction (at the fiber endings) of individual action potentials generated by motor units of the sphincters.

A linear array of electrodes printed on a plastic band glued on the tip of the index finger of a surgical glove allows is used to detect signals from the puborectalis muscles. The anatomical features (fiber length, orientation, location of innervation zone) of motor units of these muscles can be observed with this technique. The application to the anal sphincter is particularly useful for the identification of innervation zones and the proper planning of episiotomy to reduce the risk of anal sphincter damage during child birth.