A system model that focuses on kinematic synergy for understanding human control structure

Human locomotion is a complex system generated by redundant actuators and its interaction with environment. Human manages the redundant body with dexterity for adapting to various environments. Analytical studies have revealed that multiple joints and muscles move simultaneously as if the motion is constraint in low-dimensional structures. These low-dimensional structures, called synergy, should reflect the human control strategy. Neural mechanism that probably contributes on the formation of synergy has been indicated and behavioral evidence that shows the contribution of synergy on neural control has been shown. However, behavioral approaches could not distinguish the active (neural) control and reaction from environment, thus it was difficult to discuss the control characteristic of synergy. The present research proposed a system model based on physiological knowledge about kinematic synergy, and performed a dynamical simulation on flat and slope floors. Based on the resultant motion on different environment, the effect of reaction from environment on walking posture, and the contribution of three kinematic synergies on walking control were revealed.