Measures of gait stability: performance on adults and toddlers at the beginning of independent walking.

Maria Cristina Bisi,Federico Riva,Rita Stagni

doi:10.1186/1743-0003-11-131

Abstract

BackgroundQuantifying gait stability is a topic of high relevance and a number of possible measures have been proposed. The problem in validating these methods is the necessity to identify a-priori unstable individuals. Since proposed methods do not make any assumption on the characteristics of the subjects, the aim of the present study was to test the performance of gait stability measures on individuals whose gait is a-priori assumed unstable: toddlers at the onset of independent walking.MethodsTen toddlers, ten adults and ten elderly subjects were included in the study. Data from toddlers were acquired longitudinally over a 6-month period to test if the methods detected the increase in gait stability with experience, and if they could differentiate between toddlers and young adults. Data from elderly subjects were expected to indicate a stability value in between the other two groups. Accelerations and angular velocities of the trunk and of the leg were measured using two tri-axial inertial sensors. The following methods for quantifying gait stability were applied: stride time variability, Poincaré plots, harmonic ratio, short term Lyapunov exponents, maximum Floquet multipliers, recurrence quantification analysis and multiscale entropy. An unpaired t-test (level of significance of 5%) was performed on the toddlers and the young adults for each method and, for toddlers, for each evaluated stage of gait development.ResultsMethods for discerning between the toddler and the adult groups were: stride time variability, Poincaré plots, harmonic ratio, short term Lyapunov exponents (state space composed by the three linear accelerations of the trunk), recurrence quantification analysis and multiscale entropy (when applied on the vertical or on the antero-posterior L5 accelerations).ConclusionsResults suggested that harmonic ratio and recurrence quantification analysis better discern gait stability in the analyzed subjects, differentiating not only between unstable toddlers and stable healthy adults, but also evidencing the expected trend of the toddlers towards a higher stability with walking experience, and indicating elderly subjects as stable as or less stable than young adults.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-0003-11-131) contains supplementary material, which is available to authorized users.

Highlights

Quantifying gait stability is a topic of high relevance and a number of possible measures have been proposed
The general purpose of the present study was to test the performance of gait stability measures proposed and applied in the literature [1,2,3,4,5] on individuals who experience more than one fall every day, considered unstable by definition: toddlers at the onset of independent walking
Jarque-Bera test results confirmed the normal distribution of the estimated parameters for young adults, elderly adults and toddlers; for toddlers, parameters resulted normally distributed at each developmental stage

Summary

Introduction

Quantifying gait stability is a topic of high relevance and a number of possible measures have been proposed. The general purpose of the present study was to test the performance of gait stability measures proposed and applied in the literature [1,2,3,4,5] on individuals who experience more than one fall every day, considered unstable by definition: toddlers at the onset of independent walking. Toddlers at their first steps are surely at high risk for falls, and during months of walking experience they fall less and less increasing their stability [8]. With each day of walking, they take more steps, travel farther distances, and fall less: better walkers spontaneously walk more and fall less [9]

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