The understanding of impaired neural control of gait after stroke is important to evaluate mobility impairments focused on improving walking function. Previous studies have shown that the central nervous system may control gait via muscle synergies, which modularly organizes multiple muscles. However, there are insufficient studies to evaluate mobility impairments, using muscle synergy during walking in post-stroke patients. Thus, the purpose of this study was to determine if the variability of muscle synergies during gait reflects impaired motor performance. Electromyography (EMG) signals were collected from five persons with post-stroke hemiparesis and five similarly age healthy persons, as they walked on a treadmill at a comfortable speed. EMG signals were decomposed using non-negative matrix factorization and the variability of muscle synergies was calculated using a synergy stability index (SSI). We also investigated correlation between the SSI and Fugl-Meyer assessment and Berg Balance Scale, which are clinical evaluation indicators. Post-stroke patients were found to have variable muscle synergies. We also observed a positive proportional relation, between SSI and clinical motor impair evaluation indicators. These results could yield a quantitative assessment of gait after stroke, and provide a causal relationship between internal neuromuscular mechanisms and functional performance.

Since most commercialized DLP 3D printers fabricate 3D structures by sinking materials to Vat using a bottom-up method, it is difficult to use various materials simultaneously and there are many restrictions on printing composite materials. Especially, composite resin mixed with various functional powders in photo curable resin generally has high viscosity, causing difficult material flow in the bottom-up method when using Vat. Additionally, most of the previously presented methods for fabricating multi-material structure use individual curing for each material, so the adhesion force at the contact surface is less than 50% compared to single material. Thus, in this paper, we propose a new type of DLP 3D printer that combines Material Extrusion and the DLP system. The proposed equipment can supply high viscosity composite material resins to a specific area to cure various materials simultaneously. This method will enable fabrication of multiple composite material structures with sufficient adhesion force. The tensile test will be performed to verify suitability of the proposed method.