Posture Sway and the Transition Rate for a Fall

Postural body sway displacements for quiet standing subjects (measured with a new ultrasonic device) are reported. Two of the well known strategies for balancing, namely ankle and hip movements were probed. The data is modeled using a Fokker-Plank-Langevin stochastic theory. Both analytic and computer simulation techniques are employed. The Kramers transition rate for a fall is expressed as a function of experimental parameters. The root mean square velocity is especially important in determining the fall probability.