Individual margins of instanteneous dynamic stability: A preliminary study on periodic and roller skating motion

Abstract

The purpose of this study was to establish individual margins of instantaneous dynamic stability during human locomotion. A set of simple conditions and indices for instantaneous dynamic stability were derived based on the periodicity of human locomotion. Kinematic data during periodic and fall prone locomotion of seven healthy subjects was collected by using a set of wearable and wireless measurement devices. For individual subject, the margins of instantaneous dynamic stability were established on the clear distinctions between the stability indices obtained from periodic and falling-over skating motions. A sensitivity analysis was used to establish the proper combination of stability margins providing the robust notification of fall tendency in no shorter than 2 seconds before fall hit. The fall tendency was evaluated at every stepwise of the recorded kinematic data, after the stability indices were initially calculated from the first motion cycle. By varying one-factor-at-a-time (OFAT), the correlation between the established margins and corresponding noticed times before the fall hit was -1. The subject-specific combination of four margins of stability improved the robustness of instantaneous notification of individual subject's fall tendency.