Neuromuscular electrical stimulation (NMES) can alter the functioning of muscles and even assist muscle rehabilitation. In this paper, we evaluate the effect of NMES on the conduction velocity (CV) of the brachial biceps' motor units. We used a linear array of electrodes to acquire electromyographic signals, as different subjects perform isometric voluntary contractions (IVCs), with and without prior NMES. Our results show that, after NMES, the CVs at the beginning of the IVCs tend to increase, with respect to the case without NMES. Also, we observed that, while in the absence of NMES, the CVs tend to decrease over time with continued IVCs, this does not happen after 20 minutes of NMES, and the CVs can, in some cases, increase with the contractions.