[Biomechanical Analysis of Posture and Movement Coordination in Standing Human During Trunk Bending in the Sagittal Plane].

In most motor acts to achieve a behavioral goal requires coordination of posture and movement. In this paper, such coordination is studied by the example of human trunk bending in. the sagittal plane. Such movements are difficult to study because both components of this motor act (main - bending per se, and "accessory" - posture aimed on equilibrium. maintenance) involve massive movements of body segments, which complicates separation of these components. Their separation is based on the modem ideas about the special features of the posture component as compared with the main component. It is shown that the main and posture components correspond to the move- ments along eigenvectors of the dynamic equation. These movements are unique because they demonstrate at the same time "kinematic" as well as "dynamic" synergies. They were called there- fore "natural synergies". The coordination of natural synergies is investigated in human during standing on the wide and narrow supports. It is shown that the experimentally observed coordination is close to optimal, providing minimum movement of the center of pressure. This ensures the center of pressure Position keeping inside the support area that is necessary for equilibrium maintenance.