Journal of Rehabilitation Research & Development (JRRD)

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Volume 50 Number 4, 2013
   Pages 555 — 572

Abstract — Changes in passive ankle stiffness and its effects on gait function in people with chronic stroke

Anindo Roy, PhD;1–2* Larry W. Forrester, PhD;1–3 Richard F. Macko, MD;1–4 Hermano I. Krebs, PhD1,5

1Department of Neurology, University of Maryland School of Medicine, Baltimore, MD; 2Maryland Exercise and Robotics Center of Excellence, Baltimore Department of Veterans Affairs Medical Center (VAMC), Baltimore, MD; 3Department of Physical Therapy and Rehabilitation Science, University of Maryland School of Medicine, Baltimore, MD; 4Geriatric Research Education and Clinical Center, Baltimore VAMC, Baltimore, MD; 5Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA

Abstract — Mechanical impedance of the ankle is known to influence key aspects of ankle function. We investigated the effects of robot-assisted ankle training in people with chronic stroke on the paretic ankle’s passive stiffness and its relationship to overground gait function. Over 6 wk, eight participants with residual hemiparetic deficits engaged in a visuomotor task while seated that required dorsiflexion (DF) or plantar flexion (PF) of their paretic ankle with an ankle robot ("anklebot") assisting as needed. Passive ankle stiffness (PAS) was measured in both the trained sagittal and untrained frontal planes. After 6 wk, the PAS decreased in both DF and PF and reverted into the variability of age-matched controls in DF. Changes in PF PAS correlated strongly with gains in paretic step lengths (Spearman rho = −0.88, p = 0.03) and paretic stride lengths (Spearman rho = −0.82, p = 0.05) during independent floor walking. Moreover, baseline PF PAS were correlated with gains in paretic step lengths (Spearman rho = 0.94, p = 0.01), paretic stride lengths (Spearman rho = 0.83, p = 0.05), and single-­support stance duration (Spearman rho = 0.94, p = 0.01); and baseline eversion PAS were correlated with gains in cadence (Spearman rho = −0.88, p = 0.03). These findings suggest that ankle robot-assisted, visuomotor-based, isolated ankle training has a positive effect on paretic ankle PAS that strongly influences key measures of gait function.

Key words: ankle impairment, ankle robot, ankle stiffness, chronic stroke, foot drop, hemiparetic gait, lower limb, motor control, rehabilitation, robotic therapy.


View HTML  ¦  View PDF  ¦  Contents Vol. 50, No. 4
This article and any supplementary material should be cited as follows:
Roy A, Forrester LW, Macko RF, Krebs HI. Changes in passive ankle stiffness and its effects on gait function in people with chronic stroke. J Rehabil Res Dev. 2013; 50(4):555–72.
http://dx.doi.org/10.1682/JRRD.2011.10.0206
ResearcherID/ORCID: Anindo Roy, PhD: E-4312-2012
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Last Reviewed or Updated  Monday, July 29, 2013 10:23 AM

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