Human Sway on a Balance Platform

In the body balance process control, a variety of postural strategies for balance recovery are used. Postural strategies are automatic stable muscular patterns. Such a mechanism reduces the degrees of freedom number, simplifies, speeds up the posture adjustment, and minimizes energy expenditure. They relate to the existence of some motor coordination sets and describe three mobility strategies: ankle, hip, and step strategy. The hip strategy occurs when interference is greater or the use of the ankle strategy is impossible, for example, due to the delay of the postural information cycle. From a dynamical systems point of view, a human attempting to balance upright on an unstable balance board represents the coupling of two dynamical systems, the human balance system with neuromuscular feedback supported on the balance board (an inverted pendulum). The coupling of these two dynamical systems, with time delay and nonlinearities, creates an ideal setting for the emergence of complex postural behaviour and unanticipated interactions between the individual, task, and the external dynamical system. The article presents an analysis of the pendulums concerning the issue of maintaining balance by man.