Posture Dependent Spatiotemporal Modulation of Dynamic Torques During Sit-to-Stand Movements

Flexibility of patterned multi-joint movements, such as sit-to-stand (STS) motions, is an important factor to ensure the stable behaviors in daily life. Knowledge on detailed mechanism to modulate the pattern of motion is, however, limited so far. Here, quantitative variations of spatiotemporal modular structure of dynamic torques during STS motions were analyzed using complex principal component analysis. The result showed that modulation of two simple parameters could account for the posture-dependent pattern changes, i.e., magnitude of control signal and temporal phase of the torques in the modules. The role of synergistic sensory input from the initial posture on spatiotemporal organization of the motion pattern was suggested.