Maintaining upright posture during visual control of the common center of pressure in different standing conditions

Motion of the common center of pressure (CCP) and center of pressure (CP) of each leg was studied in subject standing by each leg on separate force platform. Subject maintained the vertical posture during ordinary standing and during standing with visual feedback from the CCP position presented on the monitor. In both conditions the body weight was either symmetrically distributed between legs or partially transferred to right or to left leg. During standing with symmetrical loading of both legs the visual feedback led to the decrease the standard deviation of CCP and CP of each leg. After the transfer of the body weight on one leg standard deviation of the CCP and CP of each leg was not changed when the visual feedback was present. It is likely that the afferentation from loaded leg was sufficient for define the equilibrium body position. The velocity of motion of CCP increased with presence of the visual feedback during standing with all variants of weight distribution. The velocity of motion of CP of left leg increased with visual feedback during standing with symmetrical load and with load of the right leg. The velocity of motion of CP of right leg increased with visual feedback during standing load of the left leg. One could suggest that the tracking of the CCP position was mainly occurred by the leg that less involved into postural control. During standing with symmetrical weight distribution the afferentation from dominant leg more significant for the elaboration of referent body position for maintaining of vertical posture and the tracking CCP position influenced greater on the motion of the CP of the nondominant left leg. During standing with asymmetrical weight distribution the loaded leg is more involved into postural control and the tracking CCP position occurred by unloaded leg. It is suggested that the elaboration of referent body position for maintaining of vertical posture require the stationary position for leg that was mainly involved into postural control.