The patient participated in the hybrid gait training testing session (HGTT) to determine the feasibility of overground control of walking with Kinesis. Prior to the HGTT, the patient underwent a stimulation test and a training session in separate days. The stimulation test was employed to quantify the muscular response to the muscle stimulation and also to get the patient used to the stimulation. Within this stimulation test, both flexor and extensor knee muscle groups of both legs were stimulated for 15 min. The results from the stimulation test are showed in Table 2. The only noticeable finding was a reduced performance of the left leg’s flexor muscles.

After the stimulation test, a training session took place in which the subject carried out learning exercises with the Kinesis system. In this training session the basic walking technique was explained to the user (bend to the side to lift the heel prior to initiate a step and then pressing a manual button). Kinesis was adjusted to the patient anthropometry within this session. Total time walking in this training session did not exceed from 10 min. During HGTT kinesis hybrid-cooperative controller modulated both stimulation and robotic assistance during walking.

The analysis of feasibility was performed at the biomechanical level. We assessed the actual knee joint kinematics and stiffness during overground hybrid control of gait. In Fig. 1, the kinematic pattern designed to meet patient’s left knee angular limitation is showed (blue curves, light blue curves are actual knee angle). Looking at the right leg, high interaction forces towards flexion during stance were appreciated (Fig. 1c, d red curve, leg over exoskeleton). These flexor forces reflected on the kinematics, where the right knee is flexed during stance. In contrast, the interaction forces of the left leg during stance were lower, and the actual knee angle during stance remained close to the reference. Transition from stance to swing phase of the right leg resulted also on a transition of the interaction forces from flexor direction for stance, to markedly extensor direction for swing. Stimulation of flexor muscles for both legs exhibited in general a saturated pattern for the swing phase (black curves).