Effects of a passive exoskeleton on the mechanical loading of the low back in static holding tasks

Axel S. Koopman, Idsart Kingma*, Gert S. Faber, Michiel P. de Looze, Jaap H. van Dieën

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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Abstract

With mechanical loading as the main risk factor for LBP in mind, exoskeletons are designed to reduce the load on the back by taking over a part of the required moment. The present study assessed the effect of a passive exoskeleton on back and abdominal muscle activation, hip and lumbar flexion and on the contribution of both the human and the exoskeleton to the L5/S1 net moment, during static bending at five different hand heights. Two configurations of the exoskeleton (LOW & HIGH) differing in angle-torque characteristics were tested. L5/S1 moments generated by the subjects were significantly reduced (15–20% for the most effective type) at all hand heights. LOW generated 4–11 Nm more support than HIGH at 50%, 25% and 0% upright stance hand height and HIGH generated 4–5 Nm more support than LOW at 100% and 75%. Significant reductions (11–57%) in back muscle activity were found compared to WITHOUT for both exoskeletons for some conditions. However, EMG reductions compared to WITHOUT were highly variable across subjects and not always significant. The device allowed for substantial lumbar bending (up to 70°) so that a number of participants showed the flexion-relaxation phenomenon, which prevented further reduction of back EMG by the device and even an increase from 2% to 6% MVC in abdominal activity at 25% hand height. These results indicate that flexion relaxation and its interindividual variation should be considered in future exoskeleton developments.

Original languageEnglish
Pages (from-to)97-103
Number of pages7
JournalJournal of Biomechanics
Volume83
Early online date26 Nov 2018
DOIs
Publication statusPublished - 23 Jan 2019

Funding

The authors would like to acknowledge the support of Laevo for unconditionally providing the exoskeleton for this research. This work was supported by the European Union’s Horizon 2020 through the SPEXOR project, contract no. 687662 .

FundersFunder number
Horizon 2020 Framework Programme687662
European Commission

    Keywords

    • Low-back pain
    • Mechanical loading
    • Passive exoskeletons
    • Static holding

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