Walking cycle recording and analysis for FNS-assisted paraplegic walking

In closed-loop functional neuromuscular stimulation (FNS)-assisted paraplegic walking, there is a need for reference leg motion trajectories that describe the desired walking cycle. These reference trajectories were defined as the angular changes between the leg segments, as measured by an electrogoniometer system. For each leg, the hip, knee and ankle trajectories of normal individuals during slow walking were measured and sampled over a number of cycles. Additionally, foot contact with the ground was measured to synchronise the various walking trajectories. Each joint's angular trajectory was averaged over a number of walking cycles, using an interpolation method based on a discrete Fourier transform (DFT) and inverse DFT technique, to expand all the signals to the same length. In this way an average walking cycle was obtained for each trial, representing the six averaged leg motion trajectories for one walking cycle. Angular trajectories and walking parameters for slow and normal walking were compared so as to investigate principles of walking cycle adaptation necessary to stabilise the body during slow walking. In general, angular trajectories were similar for different subjects, but different for different walking speeds, due to the greater demands on maintaining stability during slow walking. It can be concluded that normal speed walking consists of separate, unstable phases, whereas slow speed walking, relevant for paraplegic walking, requires stabilising each separate phase of the walking cycle.