Does the coordination between posture and movement during human whole-body reaching ensure center of mass stabilization?
The whole-body center of mass (CoM) has been classically regarded as the stabilized reference value for human voluntary movements executed upon a fixed base of support. Axial synergies (opposing displacements of head and trunk with hip segments) are believed to minimize antero-posterior (A/P) CoM displacements during forward trunk movements. It is also widely accepted that anticipatory postural adjustments (APAs) create forces of inertia that counteract disturbances arising from the moving segment(s). In the present study, we investigated CoM stabilization by axial synergies and APAs during a whole-body reaching task. Subjects reached towards an object placed on the ground in front of them in their sagittal plane using a strategy of coordinated trunk, knee, and hip flexion. The reaching task imposed constraints on arm-trajectory formation and equilibrium maintenance. To manipulate equilibrium constraints, differing conditions of distance and speed were imposed. The comparison of distan
