Joint coordination in young and older adults during quiet stance: effect of visual feedback of the center of pressure.

How aging affects body sway and joint coordination during quiet standing was investigated under two visual feedback conditions provided on a monitor screen: fixed and moving cursor representing the center of pressure (COP) position measured by a platform. The across-time joint motion variance of ankle, knee, hip, mid-trunk, and cervical spine leading to COP displacement was analyzed using the uncontrolled manifold approach. The body sway was assessed by the COP displacement. Young and older adults showed greater ankle joint contribution to COP displacement than the other joints. However, older adults showed larger variability of knee and mid-trunk joint motions than young adults. During the moving condition, the ankle joint contribution decreased and hip joint contribution increased for both groups, but the COP displacement increased only for the older adults. We conclude that joint coordination and body sway during quiet standing can be modified by providing COP visual feedback and that joint coordination is affected by aging.