Fig. 1

Electrodes’ and US probe positioning. a, shows the position of stimulation electrodes over the fibular nerve and of the 64 recording electrodes (8 × 4 arrangement) over the tibialis anterior (TA) muscle. See methods for detailed information on how the electrode grid was positioned over TA. Electrodes in the grid considered to simulate the conventional, bipolar detection are indicated with black circles. b, illustrates the three ankle joint positions for which the amplitude of M waves was quantified