Figure 7.

The monopolar recordings of a motor unit action potential (MUAP) by two different electrodes, G1 and G2. The location of G2 remains between the innervation zone (IZ) and the muscle–tendon junction, while G1 is moved closer to G2 to decrease the distance between them (top panels (A–E)). The bottom panels show the difference between the two monopolar MUAP recordings to construct a bipolar MUAP, as would occur with differential amplification, for each distance between G1 and G2. The sign conventions are G1 (+) and G2 (−), which means that the input to G1 is unaltered and the input to G2 is inverted by the op-amp and now displayed so the depolarization phase is positive above the horizontal zero line. The x-axis is the time-evolution of the MUAP in milliseconds for CV = 4 m/s.