Intermittent control in human balancing on an unstable and unrestrained platform

Abstract

The presence of an intermittent control strategy in human quiet standing and various balancing tasks is established in the literature. In intermittent control, the variables of interest are monitored continuously but corrective action is only taken intermittently when the variables exceed certain threshold criteria. It is however unclear whether an intermittent control strategy is employed in other balancing tasks such as standing (and balancing) on an unrestrained, unstable platform. In this paper, we study a simple, unrestrained anterior-posterior rocker balancing task using both experimental investigation with human subjects and numerical simulations, to evaluate the presence of an intermittent strategy. For experimental data, we conducted a pilot study with 5 human subjects undertaking both a quiet standing task and a rocker balancing task. For numerical simulations, we employ a Rolling Disk coupled with an Inverted Pendulum (RDIP) model with continuous and intermittent control representing the rocker balancing task and a Simple Inverted Pendulum (SIP) model to represent the quiet standing task. The data and analysis from the experimental study and numerical simulations provide evidence for the presence of an intermittent control strategy in rocker balancing with reduced intermittency and higher postural fluctuations compared to quiet standing.