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ORIGINAL RESEARCH article

Front. Hum. Neurosci.
Sec. Motor Neuroscience
Volume 18 - 2024 | doi: 10.3389/fnhum.2024.1367952

Causal interactions and dynamic stability between limbs walking with imposed leg constraints

Provisionally accepted
Genevieve K. Williams Genevieve K. Williams 1*Domenico Vicinanza Domenico Vicinanza 2Michael Attias Michael Attias 3Stéphane Armand Stéphane Armand 4,5
  • 1 University of Exeter, Exeter, United Kingdom
  • 2 Anglia Ruskin University, Cambridge, East of England, United Kingdom
  • 3 University of Applied Sciences and Arts of Western Switzerland, Delémont, Jura, Switzerland
  • 4 Hôpitaux universitaires de Genève (HUG), Genève, Geneva, Switzerland
  • 5 University of Geneva, Geneva, Geneva, Switzerland

The final, formatted version of the article will be published soon.

    Aim: To investigate the dynamics of the motor control system during walking by examining the complexity, stability, and causal relationships of leg motions. Specifically, the study focuses on gait under both bilateral and unilateral constraints induced by a passive exoskeleton designed to replicate gastrocnemius contractures. Method: Kinematic data was collected as 10 healthy participants walked at a self-selected speed. A new Complexity-Instability Index (CII) of the leg motions was defined as a function of the Correlation Dimension and the Largest Lyapunov Exponent. Causal interactions between the leg motions are explored using Convergent Cross Mapping. Results: Normal walking is characterised by a high mutual drive of each leg to the other, where CII is lowest for both legs (complexity of each leg motion is low and stability high). The effect of the bilateral emulated contractures is a reduced drive of each leg to the other and an increased CII for both legs. With unilateral emulated contracture, the mechanically constrained leg strongly drives the unconstrained leg, and CII was significantly higher for the constrained leg compared to normal walking.Redundancy in limb motions is used to support causal interactions, reducing complexity and increasing stability in our leg dynamics during walking. The role of redundancy is to allow adaptability above being able to satisfy the overall biomechanical problem; and to allow the system to interact optimally. From an applied perspective, important characteristics of functional movement patterns might be captured by these nonlinear and causal variables, as well as the biomechanical aspects typically studied.

    Keywords: nonlinear dynamics, clinical gait analysis, Symmetry, pathological gait, exoskeleton

    Received: 09 Jan 2024; Accepted: 15 Aug 2024.

    Copyright: © 2024 Williams, Vicinanza, Attias and Armand. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Genevieve K. Williams, University of Exeter, Exeter, United Kingdom

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.