Modeling human balance

The human body is an incredibly complex dynamical system, which makes it an increasingly appealing subject for nonlinear dynamicists. For example, even when we stand upright, we are not motionless—the body oscillates continuously at a low amplitude. But as we lean farther from the vertical, our response becomes more complicated. In the language of dynamical systems, the upright position is an attractor: As long as the body is in the vicinity of that position, it will be drawn upright. The various leaning positions from which one can right oneself constitute what’s called the basin of attraction. The boundary of the basin separates the upright attractor from another attractor—the floor. If we lean too far, we fall down. studying the self-righting ability of judokas and other elite athletes, María Zakynthinaki of Madrid’s Institute for the Mathematical Sciences and colleagues at the Technical University of Madrid have shown that even when the...