Improving balance with less effort through faster-than-physiological ankle exoskeleton assistance during perturbed gait: Humans adapt fast with altered sensorimotor processing

Improving balance with less effort through faster-than-physiological ankle exoskeleton assistance during perturbed gait: Humans adapt fast with altered sensorimotor processing | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Improving balance with less effort through faster-than-physiological ankle exoskeleton assistance during perturbed gait: Humans adapt fast with altered sensorimotor processing Maura Eveld, Herman van der Kooij, Edwin van Asseldonk This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6730054/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 13 You are reading this latest preprint version Abstract Background: Supporting human balance is a crucial application of powered lower-limb exoskeletons, as proper balance control could improve user safety, reduce fall risk for populations with mobility impairments, and ultimately promote device adoption in the real world. Recent work suggests that exoskeleton balance assistance provided faster than the physiological response improves postural balance; however, this approach has not yet been investigated during gait. Thus, we aimed to test faster-than-physiological ankle exoskeleton balance assistance during perturbed gait while exploring other knowledge gaps regarding ankle exoskeleton balance control. Specifically, we investigated (1) the effects of assistance on balance performance and recovery effort, (2) the extent of adaptation to the assistance, and (3) sensorimotor processing with versus without the assistance. Methods: Thirteen adults without mobility impairments participated in an ankle exoskeleton balance study. They walked on a treadmill while wearing bilateral ankle exoskeletons and receiving unexpected forward pushes of three magnitudes from a robotic pusher device attached to their waist. Center-of-mass states, ankle moment and muscle activity, and spatiotemporal gait outcomes during push responses were assessed without balance assistance, during exposure to balance assistance for 180 pushes, and upon removal of the balance assistance. Results: With ankle exoskeleton balance assistance, participants responded to forward pushes with significantly improved balance performance (decreased center-of-mass states) and reduced recovery effort (decreased soleus muscle activity and ankle moment). Participants adapted quickly to the assistance by decreasing their ankle muscle activity and increasing their center-of-mass displacement, without aftereffects, when assistance was removed. Sensorimotor processing in response to forward pushes (relationship between center-of-mass state and resulting muscle activity) significantly differed with versus without the balance assistance. Conclusion: Faster-than-physiological ankle support may be a promising solution to improve the balance of exoskeleton users during gait, as participants exhibited better balance performance and reduced effort. Participants' quick adaptation without aftereffects provides insights into future exoskeleton training paradigms, and sensorimotor findings provide further understanding of how humans internalize the use of robotic support. Overall this work contributes to the integration of balance control into lower-limb exoskeletons, advancing toward the ultimate goal of a wearable robotic solution for individuals with balance impairments. Full Text Additional Declarations No competing interests reported. Supplementary Files AdditionalFile1Submission2025.pdf VideoAdditionalFile2.mp4 Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 28 Nov, 2025 Reviews received at journal 13 Nov, 2025 Reviews received at journal 11 Nov, 2025 Reviewers agreed at journal 06 Nov, 2025 Reviewers agreed at journal 06 Nov, 2025 Reviewers agreed at journal 06 Nov, 2025 Reviewers agreed at journal 06 Nov, 2025 Reviews received at journal 20 Sep, 2025 Reviewers agreed at journal 23 Aug, 2025 Reviewers invited by journal 18 Aug, 2025 Editor assigned by journal 26 May, 2025 Submission checks completed at journal 26 May, 2025 First submitted to journal 23 May, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6730054","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":505107262,"identity":"a1d10286-3ad6-40f4-98bf-8d943278a880","order_by":0,"name":"Maura Eveld","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA10lEQVRIiWNgGAWjYBADGYbjDXAO4wFitPAwnDnACNIkAeIRqeVGApFadBuYDzB8bLPh4bv5xvwxT8WdOn4G3gN4tZgdYEtgnNmWxiN5O8ewmefMMwnJBr4EAlp4DJh5zhzmMQBpyW07LGEAFCGghf8D858z/3kMbp4Bavl3WMKesBYeBmaGCqCyGzxALQ1AWxgIaTnMZnCwpyKZR/JMWuHsP8cOS844TEjL8eaHD34Y2MnxHT+84eOMmsP8/O09hg/waQG6Cj0WmPGqHwWjYBSMglFADAAAab1Mz4KDQtYAAAAASUVORK5CYII=","orcid":"","institution":"University of Twente","correspondingAuthor":true,"prefix":"","firstName":"Maura","middleName":"","lastName":"Eveld","suffix":""},{"id":505107263,"identity":"b3af994c-6652-48b6-bd2b-aa0d866bf3ed","order_by":1,"name":"Herman van der Kooij","email":"","orcid":"","institution":"University of Twente","correspondingAuthor":false,"prefix":"","firstName":"Herman","middleName":"van der","lastName":"Kooij","suffix":""},{"id":505107267,"identity":"0a1a8669-8877-4ee7-b327-a000caece342","order_by":2,"name":"Edwin van Asseldonk","email":"","orcid":"","institution":"University of Twente","correspondingAuthor":false,"prefix":"","firstName":"Edwin","middleName":"van","lastName":"Asseldonk","suffix":""}],"badges":[],"createdAt":"2025-05-23 06:53:25","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6730054/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6730054/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89985225,"identity":"4f011a59-9893-4ede-9559-02417c035172","added_by":"auto","created_at":"2025-08-27 06:41:03","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6268379,"visible":true,"origin":"","legend":"","description":"","filename":"JNERSubmission20255222331.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6730054/v1_covered_6f029f18-2e33-4046-b80d-f3fd63348d4b.pdf"},{"id":89983224,"identity":"3a83c2fc-f50f-4771-bc48-5762bd3140d0","added_by":"auto","created_at":"2025-08-27 06:32:58","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":302223,"visible":true,"origin":"","legend":"","description":"","filename":"AdditionalFile1Submission2025.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6730054/v1/cfdc3e115d16b362e671ea85.pdf"},{"id":89983303,"identity":"569305e3-cf57-4bd9-89e8-2792b1f7b902","added_by":"auto","created_at":"2025-08-27 06:33:14","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":361948335,"visible":true,"origin":"","legend":"","description":"","filename":"VideoAdditionalFile2.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6730054/v1/c746faf2ecd6f80865caf7c2.mp4"}],"financialInterests":"No competing interests reported.","formattedTitle":"Improving balance with less effort through faster-than-physiological ankle exoskeleton assistance during perturbed gait: Humans adapt fast with altered sensorimotor processing","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-neuroengineering-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jner","sideBox":"Learn more about [Journal of NeuroEngineering and Rehabilitation](http://jneuroengrehab.biomedcentral.com/)","snPcode":"12984","submissionUrl":"https://submission.nature.com/new-submission/12984/3","title":"Journal of NeuroEngineering and Rehabilitation","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6730054/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6730054/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e Supporting human balance is a crucial application of powered lower-limb exoskeletons, as proper balance control could improve user safety, reduce fall risk for populations with mobility impairments, and ultimately promote device adoption in the real world. Recent work suggests that exoskeleton balance assistance provided faster than the physiological response improves postural balance; however, this approach has not yet been investigated during gait. Thus, we aimed to test faster-than-physiological ankle exoskeleton balance assistance during perturbed gait while exploring other knowledge gaps regarding ankle exoskeleton balance control. Specifically, we investigated (1) the effects of assistance on balance performance and recovery effort, (2) the extent of adaptation to the assistance, and (3) sensorimotor processing with versus without the assistance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e Thirteen adults without mobility impairments participated in an ankle exoskeleton balance study. They walked on a treadmill while wearing bilateral ankle exoskeletons and receiving unexpected forward pushes of three magnitudes from a robotic pusher device attached to their waist. Center-of-mass states, ankle moment and muscle activity, and spatiotemporal gait outcomes during push responses were assessed without balance assistance, during exposure to balance assistance for 180 pushes, and upon removal of the balance assistance.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e With ankle exoskeleton balance assistance, participants responded to forward pushes with significantly improved balance performance (decreased center-of-mass states) and reduced recovery effort (decreased soleus muscle activity and ankle moment). Participants adapted quickly to the assistance by decreasing their ankle muscle activity and increasing their center-of-mass displacement, without aftereffects, when assistance was removed. Sensorimotor processing in response to forward pushes (relationship between center-of-mass state and resulting muscle activity) significantly differed with versus without the balance assistance.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e Faster-than-physiological ankle support may be a promising solution to improve the balance of exoskeleton users during gait, as participants exhibited better balance performance and reduced effort. Participants' quick adaptation without aftereffects provides insights into future exoskeleton training paradigms, and sensorimotor findings provide further understanding of how humans internalize the use of robotic support. Overall this work contributes to the integration of balance control into lower-limb exoskeletons, advancing toward the ultimate goal of a wearable robotic solution for individuals with balance impairments.\u003c/p\u003e","manuscriptTitle":"Improving balance with less effort through faster-than-physiological ankle exoskeleton assistance during perturbed gait: Humans adapt fast with altered sensorimotor processing","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-27 06:32:52","doi":"10.21203/rs.3.rs-6730054/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-28T21:10:14+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-13T16:33:19+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-11T17:52:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"162833886132353660300070986960368886465","date":"2025-11-06T22:45:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"291584604241708889993354718932602201769","date":"2025-11-06T21:08:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"70380952857648157026368085482645964963","date":"2025-11-06T21:07:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"205785021377186132666488360840939007529","date":"2025-11-06T20:32:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-20T20:29:22+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"325397273876583195791318343931430323838","date":"2025-08-24T01:45:29+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-18T22:58:48+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-26T07:26:57+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-26T07:26:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of NeuroEngineering and Rehabilitation","date":"2025-05-23T06:42:53+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-neuroengineering-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jner","sideBox":"Learn more about [Journal of NeuroEngineering and Rehabilitation](http://jneuroengrehab.biomedcentral.com/)","snPcode":"12984","submissionUrl":"https://submission.nature.com/new-submission/12984/3","title":"Journal of NeuroEngineering and Rehabilitation","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"59bb65b6-aac1-441d-81c9-a2582914dffc","owner":[],"postedDate":"August 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-06T02:23:17+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-27 06:32:52","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6730054","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6730054","identity":"rs-6730054","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}