Influence of specific sensory inputs on standing balance in healthy adults : focused on the difference between head sway and COP sway

As different sensory inputs may lead to different balance control strategy, head sway, which closely influences the visual and vestibular sensorium, is of great significance in human postural control. In the proposed research, we evaluate the effects of sensory input disturbances in healthy adults at quiet standing by comparison between head sway and center of pressure (COP) sway. Twenty subjects (age: 24.3±3.0) without known impairments take part in the test. Head sway measured by the Computer-Aided Cephalogram (CAC) method and COP sway measured by a force plate are evaluated. Experimental conditions: eyes open and eyes closed respectively, hard support surface and soft support surface respectively. Results show that: Compared with that under condition of less sensorium information inputs (eyes closed soft support surface), the standing posture with more sensorium information inputs (eyes open, hard support surface) has the following characteristics: (1) In addition to the ankle, other joints take more effect with the posture maintenance, and thus the body is controlled more flexibly; (2) compared with the sways in A/P direction, the sways in M/L direction which is mechanically more unstable is better controlled. (3) As a consequence of the first two control strategies, the COP and head sways turn to be more moderate with smaller sways