Lyapunov exponent and surrogation analysis of patterns of variability: Profiles in new walkers with and without down syndrome

Beth A. Smith, Nick Stergiou, Beverly D. Ulrich

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

In previous studies we found that preadolescents with Down syndrome (DS) produce higher amounts of variability (Smith et al., 2007) and larger Lyapunov exponent (LyE) values (indicating more instability) during walking than their peers with typical development (TD) (Buzzi & Ulrich, 2004). Here we use nonlinear methods to examine the patterns that characterize gait variability as it emerges, in toddlers with TD and with DS, rather than after years of practice. We calculated Lyapunov exponent (LyE) values to assess stability of leg trajectories. We also tested the use of 3 algorithms for surrogation analysis to investigate mathematical periodicity of toddlers' strides. Results show that toddlers' LyE values were not different between groups or with practice and strides of both groups become more periodic with practice. The underlying control strategies are not different between groups at this point in developmental time, although control strategies do diverge between the groups by preadolescence.

Original languageEnglish (US)
Pages (from-to)126-142
Number of pages17
JournalMotor Control
Volume14
Issue number1
DOIs
StatePublished - Jan 2010

Keywords

  • Developmental disabilities
  • Gait
  • Nonlinear analysis

ASJC Scopus subject areas

  • Physical Therapy, Sports Therapy and Rehabilitation
  • Clinical Neurology
  • Physiology (medical)

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