an alternative approach to the above techniques is the fes system for walking developed using the compex motion neuroprosthesis. compex motion neuroprosthesis for walking is an eight to sixteen channel surface fes system used to restore voluntary walking in stroke and spinal cord injury individuals. this system does not apply peroneal nerve stimulation to enable locomotion. instead, it activates all relevant lower limb muscles in a sequence similar to the one that brain uses to enable locomotion. the hybrid assistive systems (has) and the rgo walking neuroprostheses are devices that also apply active and passive braces, respectively. the braces were introduced to provide additional stability during standing and walking. a major limitation of neuroprostheses for walking that are based on surface stimulation is that the hip flexors cannot be stimulated directly. therefore, hip flexion during walking must come from voluntary effort, which is often absent in paraplegia, or from the flexor withdrawal reflex. implanted systems have the advantage of being able to stimulate the hip flexors, and therefore, to provide better muscle selectivity and potentially better gait patterns. hybrid systems with exoskeleton have been also proposed to solve this problem. these technologies have been found to be successful and promising, but at the present time these fes systems are mostly used for exercise purposes and seldom as an alternative to wheelchair mobility.