Stability and energy criteria in healthy and paraplegic subject gait.

The functional electrical stimulation (FES) assisted gait of paraplegic patients is inferior to that of healthy subjects. The difference can be observed in terms of speed, upright balance, biomechanical energy consumption, and generation of propulsion forces in the direction of walking. The biomechanical structure of paraplegic subjects is the same as that of normal ones; however, the mode of walking differs significantly because of the reduced number of activated muscles and primitive control. The healthy subject is utilizing a 2-point dynamically stable gait. The paraplegic patient is using 4-channel FES and utilizing a 4-point statically stable gait. We believe that the FES gait can be improved if converted into a semidynamically or dynamically stable gait. The gait is considered statically stable if the center of gravity (COG) projection on the ground (PCOG) is inside the supporting area. For a quadruped, this is only possible if it is utilizing a creeping crawl gait. In this paper, the relationship between PCOG and the supporting area are discussed as a criterion for dynamic stability assessment. Results are shown for 3 different modes of 2-point and 4-point gaits.