Title: Correlation between ankle stiffness and antagonist co-activation in post-stroke subjects

Authors: Edgar Ribeiro; Augusta Silva; Liliana Pinho; Rubim Santos; Francisco Pinho; Andreia S.P. Sousa

Addresses: Center for Rehabilitation Research – Human Movement System (Re)habilitation Area, School of Health, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida, 400, 4200-072, Porto, Portugal ' Department of Physiotherapy, Center for Rehabilitation Research – Human Movement System (Re)habilitation Area, School of Health, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida, 400, 4200-072, Porto, Portugal ' Department of Physiotherapy, Center for Rehabilitation Research – Human Movement System (Re)habilitation Area, School of Health, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida, 400, 4200-072, Porto, Portugal; Department of Physiotherapy, CESPU, Institute of Research and Advanced Training in Health Sciences and Technologies, Rua Central da Gandra, 1317, 4585-116, Gandra, Portugal ' Department of Physics, Center for Rehabilitation Research – Human Movement System (Re)habilitation Area, School of Health, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida, 400, 4200-072, Porto, Portugal ' Department of Technologies of Diagnostic and Therapeutic, CESPU, Institute of Research and Advanced Training in Health Sciences and Technologies, Rua Central da Gandra, 1317, 4585-116, Gandra, Portugal; Department of Engineering, Collaborating Member of Applied Artificial Intelligence Laboratory, Polytechnic Institute of Cávado and Ave., Lugar do Aldão, 4750-810, Vila Frescainha – São Martinho, Barcelos, Portugal ' Department of Physiotherapy, Center for Rehabilitation Research – Human Movement System (Re)habilitation Area, School of Health, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida, 400, 4200-072, Porto, Portugal

Abstract: Tonus dysfunction has been broadly investigated in post-stroke subjects through the evaluation of muscle resistance against stretching, however, its characterisation in functional context is challenging. This study aims to analyse the correlation between intrinsic stiffness, functional stiffness and antagonist co-activation at the ankle joint of post-stroke subjects. Both lower limbs of eight post-stroke participants were evaluated. Intrinsic stiffness was assessed during passive dorsiflexion by an isokinetic dynamometer, functional stiffness during upright standing on a force platform and antagonist co-activation was obtained in upright standing and postural phases of gait initiation and stand-to-sit through the electromyographic signal of ankle muscles. A significant positive correlation was found between antagonist co-activation of ipsilesional tibialis anterior/soleus pair in upright standing and functional stiffness (r = 0.810; p = 0.015; 1-β; = 0.899). Antagonist co-activation seems to be related to functional stiffness in upright standing, suggesting the relevance of evaluating tonus dysfunction through motor control variables obtained under functional conditions.

Keywords: tonus; postural control; movement; ankle; stiffness; antagonist co-activation; upright standing; gait initiation; stand-to-sit; stroke.

DOI: 10.1504/IJHFE.2019.105360

International Journal of Human Factors and Ergonomics, 2019 Vol.6 No.4, pp.331 - 354

Received: 27 Apr 2019
Accepted: 14 Sep 2019

Published online: 17 Feb 2020 *

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