Stability Areas During Quiet Standing

The experiments performed in our laboratory revealed that able-bodied subjects use four different high-level control strategies to maintain stable quiet standing, and that there is a direct correlation between these control strategies and the position of the subject's center of pressure (COP). The overall COP area was divided into four zones: a high preference zone, a low preference zone, an undesirable zone and an unstable zone. Division of the COP surface into four distinct zones is a new concept which should enable researches designing standing prostheses to better understand the basic design requirements for such devices. Potential standing prostheses, that will be designed to provide stable and safe \hand free" quiet standing, should maintain the COP position in the high and low preference zones. A model that describes these four stability zones has been proposed.