Schematic of the electrode positioning, and example H-reflex and ongoing EMG waveforms from conditioning trials.

A Shown is the positioning of stimulation and recording electrodes on the left thigh (superior view). The FN cathode electrode is shown on the schematic but the rectangular anode electrode positioned on the posterior buttock is not shown. The dotted rectangles on the thigh correspond to the Q stimulation electrodes. B Example waveforms showing control and conditioned H-reflex sizes when FN (top row) was stimulated 6 ms after the tibial nerve (-6, excitatory; left trace) and when FN was stimulated 20 ms prior to tibial nerve (20 ms, inhibitory, right trace). The second row are example control and Q conditioned waveforms (note the Q doublet stimuli were applied 2.5 ms before/after that of FN (i.e. left trace -3.5 and -8.5 ms). All waveforms are the average of 20 trials. C Rectified soleus EMG traces (average of 20 trials) from a participant illustrating the heteronymous excitatory and inhibitory effects from femoral nerve (green trace) and quadriceps stimulation (red trace) onto ongoing SOL EMG. The mean background SOL EMG is displayed as the horizontal solid black line, and the dashed horizontal lines represent 1SD above and below the mean. The vertical dashed line at time 0 reflects stimulation timing for FN, whereas the Q stimulation doublet stimuli was at -2.5 and 2.5 ms. The second vertical dashed line represents the period prior to neural effects; note the presence of a Q stimulation artifact just before/after time 0 and two stimulation artifact harmonics that end prior to 18 ms post-stimulus.