In human studies, firing patterns in single motor units from chronic SCI subjects have shown differences in rate modulation (Thomas and Ross 1997), force-speed relations (Thomas et al. 1997), increases in discharge variability (Thomas et al. 2002), and prolonged duration of post-synaptic potentials in response to transient inputs using the PSF technique (Norton et al. 2008). These phenomena, especially those reflecting prolonged involuntary muscle activity in response to short duration stimuli, have been attributed to the presence of PICs in motoneurons. Recent results from Theiss (project co-investigator) et al. (2008) have also shown that administration of pharmacological agents that reduce PICs, e.g. riluzole, (which reduces NaP), decreases the flexion-withdrawal response in such a way that mimics the effects of riluzole seen in animal models. These are a right-ward bias shift and gain decrease in the input-output relation of animal spinal neurons (Kuo et al. 2006; Theiss et al. 2007). Interestingly, riluzole administration also enhanced agonist specificity in voluntary torque production by decreasing co-contraction and increasing total torque area during a maximum voluntary contraction (Theiss et al. 2008).