Functional electrical stimulation (FES) applied to tibialis anterior (TA) has been proven as a useful intervention for gait rehabilitation. Because stimulation parameters in FES-assisted walking are associated with TA activation, the objective of this study was to characterize TA electromyography (EMG) among four terrains, including normal walking, obstacle crossing, and stairs ascending and descending. Six healthy subjects participated in the experiment and TA EMG, lower limb kinematic and kinetic data were recorded simultaneously when subjects were instructed to walk on the four terrains. The results showed that there was a significant difference in the time interval from the heel-off event to the onset timing of TA activation when stairs descending was compared with normal walking, obstacle crossing and stairs ascending (P <0.05). Significant differences in EMG duration between each pair of terrains were also found (P <0.05). The normalized peak EMG amplitude of stairs ascending was significantly larger than normal walking and stairs descending (P <0.05). When terrains changed, TA activation was altered by the central nervous system for a stable landing and a forward body movement. These results may provide evidence for terrain-adaptive parameters in FES-assisted walking to correct dropfoot. 
Effect of different terrains on onset timing, duration and amplitude of tibialis anterior activation