Appropriate external perturbation on the identification of the standing balance system

Abstract

System identification is an evaluation approach for the human standing balance. In a previous study, we proposed an identification method for individual balance parameters based on the frequency response of the horizontal sway of the support surface, and verified the reliability of the identified parameters. However, the balance characteristics and reliability of identification may change depending on the stimulus magnitude of the support surface. The purpose of this study was to investigate changes in the balance characteristics and reliability of the identification according to changes in the sway amplitude of the support surface. Three types of sway amplitudes of the support surface were applied in the identification test for 10 subjects. By comparing different sway amplitudes using intraclass correlation coefficients, we found that the reproducibility of parameter identification decreased when the sway amplitude was small. Furthermore, we confirmed that the balance characteristics, such as the delay time and phase margin, change according to the difference in sway amplitude of the support surface. Consequently, balance identification requires a support surface amplitude of a certain magnitude, and it should be considered that balance characteristics vary with stimulus magnitude.