The dynamics of standing balance.

The control of standing is a complicated task that involves the action of muscles distributed over the whole body. Forces arising from gravity, external events or our own actions all tend to disturb the unstable equilibrium that preserves posture. For the central nervous system the problem of standing can be cast in terms of finding appropriate relations among body segments to maintain the desired position of the body as a whole with respect to the environment. In this review we evaluate some recent discoveries on the effects of predictable and unpredictable perturbations, and the role of perceptual information, attention and cognitive processes in the control of upright stance.