Exoskeleton for Gait Rehabilitation: Effects of Assistance, Mechanical Structure, and Walking Aids on Muscle Activations

Alice De Luca,Amy Bellitto,Antonino Massone,Martina Coscia,Laura Pellegrino,Maura Casadio,Sergio Mandraccia,Giorgia Marchesi,Laura Rossi,Clara Leoncini,Simona Gamba

doi:10.3390/app9142868

Abstract

Several exoskeletons have been developed and increasingly used in clinical settings for training and assisting locomotion. These devices allow people with severe motor deficits to regain mobility and sustain intense and repetitive gait training. However, three factors might affect normal muscle activations during walking: the assistive forces that are provided during walking, the crutches or walker that are always used in combination with the device, and the mechanical structure of the device itself. To investigate these effects, we evaluated eight healthy volunteers walking with the Ekso, which is a battery-powered, wearable exoskeleton. They walked supported by either crutches or a walker under five different assistance modalities: bilateral maximum assistance, no assistance, bilateral adaptive assistance, and unilateral adaptive assistance on each leg. Participants also walked overground without the exoskeleton. Surface electromyography was recorded bilaterally, and the statistical parametric mapping approach and muscle synergies analysis were used to investigate differences in muscular activity across different walking conditions. The lower limb muscle activations while walking with the Ekso were not influenced by the use of crutches or walker aids. Compared to normal walking without robotic assistance, the Ekso reduced the amplitude of activation for the distal lower limb muscles while changing the timing for the others. This depended mainly on the structure of the device, and not on the type or level of assistance. In fact, the presence of assistance did not change the timing of the muscle activations, but instead mainly had the effect of increasing the level of activation of the proximal lower limb muscles. Surprisingly, we found no significant changes in the adaptive control with respect to a maximal fixed assistance that did not account for subjects’ performance. These are important effects to take into careful considerations in clinics where these devices are used for gait rehabilitation in people with neurological diseases.

Highlights

In the last few years, powered exoskeletons have been used in clinical practice as rehabilitative tools for improving walking ability in people suffering for neurological diseases or injuries [1,2] and as assistive devices for allowing the most impaired to stand up and walk [3].As rehabilitative tools, robotic devices assist the physical therapists by providing task-specific, repeatable practice and increased intensity of training [4]
With the long-term goal of extending this study to people suffering from neurological diseases or injuries, here we focused on healthy subjects that do not have alterations of their muscle patterns, reducing the possibility of variable and highly subjective responses to each of the investigated aspects
To directly compare and average the EMG data from different subjects and legs, we normalized each muscle signal for its maximum value computed over all the acquisitions under the different conditions that we considered in the analyses

Summary

Introduction

In the last few years, powered exoskeletons have been used in clinical practice as rehabilitative tools for improving walking ability in people suffering for neurological diseases or injuries [1,2] and as assistive devices for allowing the most impaired to stand up and walk [3].As rehabilitative tools, robotic devices assist the physical therapists by providing task-specific, repeatable practice and increased intensity of training [4]. In the last few years, powered exoskeletons have been used in clinical practice as rehabilitative tools for improving walking ability in people suffering for neurological diseases or injuries [1,2] and as assistive devices for allowing the most impaired to stand up and walk [3]. While undoubtedly powered exoskeletons can provide non-ambulatory individuals with the ability to walk at modest speed [13], the literature highlights conflicting results for the training potential of these devices, and there is no compelling evidence that robot-assisted gait re-education improves walking function more than other rehabilitative strategies [8,9,14,15,16,17]

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