Walking dynamics are symmetric (enough)

Ankarali M. M., Sefati S., Madhav M. S., Long A., Bastian A. J., Cowan N. J.

JOURNAL OF THE ROYAL SOCIETY INTERFACE, vol.12, no.108, 2015 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 12 Issue: 108
  • Publication Date: 2015
  • Doi Number: 10.1098/rsif.2015.0209
  • Journal Name: JOURNAL OF THE ROYAL SOCIETY INTERFACE
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: symmetry, locomotion, rhythmic dynamics, cross-validation, LINEAR-MODEL SELECTION, GROUND REACTION FORCES, ABLE-BODIED GAIT, KINEMATIC SYMMETRY, LEGGED LOCOMOTION, CROSS-VALIDATION, METABOLIC COST, ENERGY-COST, STABILITY, VARIABILITY
  • Middle East Technical University Affiliated: No

Abstract

Many biological phenomena such as locomotion, circadian cycles and breathing are rhythmic in nature and can be modelled as rhythmic dynamical systems. Dynamical systems modelling often involves neglecting certain characteristics of a physical system as a modelling convenience. For example, human locomotion is frequently treated as symmetric about the sagittal plane. In this work, we test this assumption by examining human walking dynamics around the steady state (limit-cycle). Here, we adapt statistical cross-validation in order to examine whether there are statistically significant asymmetries and, even if so, test the consequences of assuming bilateral symmetry anyway. Indeed, we identify significant asymmetries in the dynamics of human walking, but nevertheless show that ignoring these asymmetries results in a more consistent and predictive model. In general, neglecting evident characteristics of a system can be more than a modelling convenience it can produce a better model.