Motor control characteristics of upper limbs in response to assistive forces during bilateral tasks.

Yuanyuan Wang,Ping Yeap Loh,Satoshi Muraki

doi:10.1371/journal.pone.0245049

Yuanyuan Wang, Ping Yeap Loh + Show 1 more

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https://doi.org/10.1371/journal.pone.0245049

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Journal: PloS one	Publication Date: Jan 7, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: Kyushu University, Chiba University

Abstract

Most research on power assist suits (PASs) that concerned PAS-human interactions has used human physical reactions as criteria to evaluate the mechanical function, however, with minimal emphasis on human reactions in response to PASs. In this study, we focused on the physiological responses of the upper limbs including muscle activity of the biceps brachii and the triceps brachii, co-activation, force steadiness (CV) and rated perceived exertion (RPE) to various patterns of bilateral assistive force, such as unilateral assistance (L0% & R67% [% = percentage of workload force, L = left arm, R = right arm], L67% & R0%, L0% & R33%, L33% & R0%), symmetrical (L0% & R0%, L33% & R33%, L67% & R67%) and asymmetrical bilateral assistance (L33% & R67%, L67% & R33%), during bilateral isometric force-matching tasks. The results showed a similar muscular response of the two arms to bilateral assistive conditions, and the muscle activity of the arm that was being observed decreased only when the assistive force that applied on itself increased, indicating that both arms may have adopted similar but independent motor control mechanisms to acclimate to the bilateral assistive forces. Comparison between the two unilateral assistances (L0% & R33% and L33% & R0%) and the two asymmetrical bilateral assistances (L33% & R67%, L67% & R33%) showed no significant differences in muscular responses, CV and RPE, indicating that bilateral assistances with bilateral interchanged assistive levels may be equally effective regardless of which arm the higher assistive force is applied to. Comparison between unilateral and symmetrical assistive conditions that have similar overall workloads (L67% & R0%, L33% & R33%, L0% & R67%) showed a lower CV and RPE score at symmetrical assistance compared with unilateral assistance, suggesting that assisting both arms with the same level simultaneously improves task performances compared with applying the assistive force to only one arm.

Highlights

Power assist suits (PASs) are wearable machines that augment human physical capabilities and have been applied to many fields
Among the results of the post hoc tests, we focused on 3 pairs of assistive conditions that have bilateral interchangeable assistive levels; we found no significant difference between L0% & R33% and L33% & R0%, L0% & R67% and L67% & R0%, and L67% & R33% and L33% & R67%
Considering that the muscle activity of the objective arms only decreased with the increase in the assistive force that was applied on itself, we concluded that both arms might have adopted a similar but independent motor control mechanism to acclimate to the bilateral external assistive forces

Summary

Introduction

Power assist suits (PASs) are wearable machines that augment human physical capabilities and have been applied to many fields. Motor control characteristics of upper limbs in response to assistive forces during bilateral tasks physical training [1, 2] or as assistive devices for daily use. Kawamoto, & Sankai (2005) evaluated the assistive method of the hybrid assistive limb robot suit by analyzing the myoelectric activities of extensor and flexor muscles [4]. Their experiments showed a significant reduction of muscle activities, confirming the effectiveness of the device and the assistive method. Human physiological interactions with robotic assistive devices must be considered during PAS development

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