The aim of the study was to employ combined longitudinal measurements of soleus (SOL) and gastrocnemii evoked V-wave and H-reflex responses to determine the site of adaptations within the central nervous system induced by 5 weeks of neuromuscular electrical stimulation (NMES) training of the plantar flexor muscles. Nineteen healthy males subjects were divided into a neuromuscular electrostimulated group (n=12) and a control group (n=7). The training program consisted of 15 sessions of isometric NMES over a 5-wk period. All subjects were tested before and after the 5-wk period. SOL, lateral gastrocnemius (LG) and medial gastrocnemius (MG) maximal H-reflex and M-wave potentials were evoked at rest (i.e., H_max and M_max, respectively) and during maximal voluntary contraction (MVC) (i.e., H_sup and M_sup, respectively). During MVC, a supramaximal stimulus was delivered which allowed us to record the peak-to-peak amplitudes of V-wave from all three muscles. The SOL, LG and MG electromyographic (EMG) activity as well as muscle activation (twitch interpolation technique) were also quantified during MVC. After training, plantar flexor MVC increased significantly by 22% (P<0.001). Torque gains were accompanied by an increase in muscle activation (+11%, P< 0.05), SOL, LG and MG normalized EMG activity (+51%, +54% and + 60%, respectively, P< 0.05) and V/M_sup ratios (+81%, +76% and + 97%, respectively, P< 0.05). H_max/M_max and H_sup/M_sup ratios for all three muscles were unchanged after training. In conclusion, the increase in voluntary torque after 5 wk of NMES training could be ascribed to an increased volitional drive from the supraspinal centers and/or adaptations occurring at the spinal level.