Human motor behavior can be generated using distributed system. In this study, human standing-up motion is focused as an important daily activity. Especially, 13 muscle activation of lower body and trunk during human standing-up motion is decomposed into small numbers of modules of synchronized muscle activation called muscle synergy. Moreover human musculoskeletal model is developed with four rigid body segment based on dynamics and anatomical characteristics of human body. Forward dynamic

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... lation with the developed model showed that four muscle synergies had their own contribution toward body function: bending forward, moving the center of mass forward, extending whole body, and decelerating the center of mass. Results also indicated that combinations of four modules of synchronized muscle activation could generate human standing-up motion rather than controlling individual muscles. In this study, we analyze the human motion in terms of distributed modules of synchronized muscle activation called muscle synergy. When humans move, they need to incorporate with their redundant body system, i.e. humans have to control larger degrees of freedom of muscles than that of joints in order to achieve the targeted kinematics. Therefore, muscle activation cannot be determined although the target kinematics is given. To solve this ill-posed problem, the concept of muscle synergy