Slow Walking in Individuals with Chronic Post-StrokeHemiparesis: Speed Mediated Effects of Gait Kinetics andAnkle Kinematics

All this just to tell us further research is needed. Useless.

Slow Walking in Individuals with Chronic Post-StrokeHemiparesis: Speed Mediated Effects of Gait Kinetics and Ankle Kinematics

Jing Nong Liang 1,*, 

Kai-Yu Ho 1, 

Yun-Ju Lee 2, 

Corey Ackley 1, 

Kiley Aki 1, 

Joshua Arias 1

and Jassie Trinh 1

Citation:Liang, J.N.; Ho, K.-Y.; Lee,Y.-J.; Ackley, C.; Aki, K.; Arias, J.;Trinh, J. 

Academic Editor:Michelle PloughmanReceived: 22 February 2021Accepted: 10 March 2021Published: 13 March 2021Publisher’s Note:MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Copyright:©   2021   by   the   authors.Licensee   MDPI,   Basel,   Switzerland.This  article  is  an  open  access  article distributed    under    the    terms    and conditions  of  the  Creative  Commons Attribution  (CC  BY)  license  (https://creativecommons.org/licenses/by/4.0/).1Department of Physical Therapy, University of Nevada, Las Vegas, NV 89154, USA;KaiYu.Ho@unlv.edu (K.-Y.H.); ackleyc3@unlv.nevada.edu (C.A.); kileyaki@gmail.com (K.A.);ariasj11@unlv.nevada.edu (J.A.); jgtrinh@gmail.com (J.T.)2Department of Industrial Engineering and Engineering Management, National Tsing-Hua University,Hsinchu 300, Taiwan; yunjulee@ie.nthu.edu.tw*Correspondence: jingnong.liang@unlv.edu; Tel.: +1-702-895-4936

Abstract:

Post-stroke rehabilitation often aims to increase walking speeds,  as faster walking is associated with improved functional status and quality of life. However, for successful community ambulation, ability to modulate (increase and decrease) walking speeds is more important than walking continuously at constant speeds. Increasing paretic propulsive forces to increase walking speed has been extensively examined; however, little is known about the mechanics of slow walking post-stroke. The primary purpose of this study was to identify the effects of increased and decreased walking speeds on post-stroke kinetics and ankle kinematics.   Fifteen individuals with chronic post-stroke hemiparesis and 15 non-neurologically impaired controls walked over an instrumented treadmill under:  slow, self-selected, and fast walking speeds.  We examined the peak propulsive forces, propulsive impulse, peak braking forces, braking impulse, and ankle kinematics under each condition.  When walking at slow walking speeds, paretic limbs were unable to reduce braking impulse and peak propulsive force or modulate ankle kinematics. Impaired modulation of paretic gait kinetics during slow walking places people post-stroke at high risks for slip-related falls. These findings suggest the need for developing gait retraining paradigms for slow walking in individuals chronically post-stroke that target the ability of the paretic limb to modulate braking forces.Keywords:post-stroke hemiparesis; walking speed; gait; slow walking; ground reaction forces1. 

Introduction

Stroke is the leading cause of adult long-term disabilities [1]. Individuals with hemiparesis resulting from a stroke possess significant impairments in locomotor function,resulting in slow walking speeds, asymmetrical gait patterns and fall risks, which negatively impacts functional or mobility independence and safety [2–4]. Faster walking speed is associated with enhanced quality of life [5], thus improving walking speed has been an important goal in stroke rehabilitation.Despite the significance of aiming to increase walking speed in people post-stroke,in the context of functional community ambulation, long durations of continuous steady-state comfortable speed walking behavior has been found to be less important and also occurs less frequently [6]. Rather, gait speed modulation (i.e., increasing and decreasing walking speed) and gait initiation/termination has been identified as important and more frequent functional tasks for successful community mobility. For example, walking is often combined with talking, or other attention demanding activities, resulting in slower walking speeds [7], or in the attempt to change directions during walking, when negotiating a turn,walking speeds would be decreased compared to walking in a straight line [8]. Additionally,when an individual walks past a stationary object, or when a moving object approaches the individual, walking speed has been observed to be decreased [9]. In non-neurologically impaired individuals, during steady state walking (constant speed conditions), gait is characterized by symmetric anterior-posterior ground reaction forces generated by the two legs. Walking speed is regulated by anterior-posterior ground reaction force impulses (i.e., propulsion and braking), where, with increases in walking speed, propulsive and braking impulses are observed to increase [10]. With decreases in walking speed, magnitude of anterior-posterior ground reaction forces, and joint angles decreased [11]. In  individuals  post-stroke,  during  steady  state  walking,  asymmetry  in  anterior-posterior  ground  reaction  forces  generated  have  been  reported,  with  less  propulsive forces generated by the paretic limbs.  Furthermore,  the more severe the hemiparesis,the greater the asymmetry in the propulsive and braking impulses observed [12].  With respect to the ability of foot-force control, during a posturally supported locomotor task,the stroke-impaired system has been reported to be capable of generating foot forces that are appropriately controlled in magnitude and direction [13]. The propulsive forces generated by the paretic leg have been reported to be predictive of walking speed [12], and,in fast treadmill walking, increased paretic propulsive forces have been observed [14],suggesting the limited but potential capabilities of the stroke-impaired system to modulate foot forces under controlled locomotor conditions. However, the kinetics during slower walking speeds have yet to be examined in people with chronic post-stroke hemiparesis. Reduction in walking speed to below comfortable walking speeds has been considered to be a relatively more complex task, where different locomotor and postural control strategies are adopted, compared to comfortable walking speeds [15–17], and thus individuals post stroke may not exhibit similar speed mediated changes compared to fast walking over the treadmill. In an intact nervous system, when walking speeds are reduced from comfortable to very slow walking speeds, the system switches from locomotor towards greater postural muscular control [15]. Faster locomotor speeds are potentially associated with greater suppression of vestibular drive, thus a reduction in walking speed would be associated with reduced suppression of this destabilizing vestibular drive. In conjunction with reduced proprioceptive input when speeds are reduced, increased dynamic instability makes slow walking more complex [18–20]. The  primary  goal  of  this  study  was  to  identify  the  effects  of  increased  (120%  of self-selected) and decreased (80% of self-selected) walking speeds on kinetics and ankle kinematics changes in people with chronic post-stroke hemiparesis. We hypothesized that in individuals with post-stroke hemiparesis, during fast walking (120% of self selected speed), paretic legs would exhibit increased speed-related changes in kinetics (i.e., increased peak propulsive forces, propulsive impulse, peak braking forces and braking impulses)and ankle kinematics, compared to self-selected walking speed, but these variables would remain unchanged during slow walking (80% of self-selected speed).