Augmenting propulsion demands during split-belt walking increases locomotor adaptation of asymmetric step lengths

Carly J Sombric,Gelsy Torres-Oviedo

doi:10.1186/s12984-020-00698-y

Carly J Sombric, Gelsy Torres-Oviedo

Open Access

https://doi.org/10.1186/s12984-020-00698-y

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Abstract

BackgroundPromising studies have shown that the gait symmetry of individuals with hemiparesis due to brain lesions, such as stroke, can improve through motor adaptation protocols forcing patients to use their affected limb more. However, little is known about how to facilitate this process. Here we asked if increasing propulsion demands during split-belt walking (i.e., legs moving at different speeds) leads to more motor adaptation and more symmetric gait in survivors of a stroke, as we previously observed in subjects without neurological disorders.MethodsWe investigated the effect of propulsion forces on locomotor adaptation during and after split-belt walking in the asymmetric motor system post-stroke. To test this, 12 subjects in the chronic phase post-stroke experienced a split-belt protocol in a flat and incline session so as to contrast the effects of two different propulsion demands. Step length asymmetry and propulsion forces were used to compare the motor behavior between the two sessions because these are clinically relevant measures that are altered by split-belt walking.ResultsThe incline session resulted in more symmetric step lengths during late split-belt walking and larger after-effects following split-belt walking. In both testing sessions, subjects who have had a stroke adapted to regain speed and slope-specific leg orientations similarly to young, intact adults. Importantly, leg orientations, which were set by kinetic demands, during baseline walking were predictive of those achieved during split-belt walking, which in turn predicted each individual’s post-adaptation behavior. These results are relevant because they provide evidence that survivors of a stroke can generate the leg-specific forces to walk more symmetrically, but also because we provide insight into factors underlying the therapeutic effect of split-belt walking.ConclusionsIndividuals post-stroke at a chronic stage can adapt more during split-belt walking and have greater after-effects when propulsion demands are augmented by inclining the treadmill surface. Our results are promising since they suggest that increasing propulsion demands during paradigms that force patients to use their paretic side more could correct gait asymmetries post-stroke more effectively.

Highlights

Promising studies have shown that the gait symmetry of individuals with hemiparesis due to brain lesions, such as stroke, can improve through motor adaptation protocols forcing patients to use their affected limb more
Those who have had a stroke were eligible if they (1) had only unilateral and supratentorial lesions as confirmed by magnetic resonance imaging (MRI), (2) were able to walk without assistance from others or a device for 5 min at a self-selected pace, (3) were free of orthopedic injury or pain that would interfere with testing, (4) had no other neurological condition other than stroke, (5) had no severe cognitive impairments defined by a MiniMental State Exam score below 24 [55], and (6) did not take medications that altered cognitive function
We focused our analysis on the propulsion component of the anterior-posterior ground reaction forces (GRF) because they are associated with walking speed, hemiparetic severity [9], and step length asymmetry [4]

Summary

Introduction

Promising studies have shown that the gait symmetry of individuals with hemiparesis due to brain lesions, such as stroke, can improve through motor adaptation protocols forcing patients to use their affected limb more. We asked if increasing propulsion demands during split-belt walking (i.e., legs moving at different speeds) leads to more motor adaptation and more symmetric gait in survivors of a stroke, as we previously observed in subjects without neurological disorders Brain lesions, such as stroke, may result in asymmetric gait, limiting patients’ mobility and decreasing their quality of life [31]. Split-belt walking (i.e., legs moving at different speeds), has been shown to reduce gait asymmetries post-stroke [7, 39,40,41, 47, 62, 63] While this is encouraging, little is understood about the mechanisms underlying this process and how to facilitate it. There is a scientific and clinical interest to identify factors that underlie the therapeutic effect of split-belt walking in order to augment rehabilitative effects

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