The effect of muscle fatigue on neuromuscular activation and force production of the quadriceps muscle

The effect of muscle fatigue on neuromuscular activation and force production of the quadriceps muscle | 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 Article The effect of muscle fatigue on neuromuscular activation and force production of the quadriceps muscle Smadar Peleg, Ophir Ravina, Moshe Ayalon This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7501643/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Muscle performance declines with fatigue; EMG mean frequency (MNF) falls linearly with repetitions, whereas root mean square (RMS) shows inconsistent individual patterns. Prior knee-extension studies used high angular velocities (≈180°·s⁻¹), emphasizing explosive power rather than maximal strength. We evaluated strength-oriented fatigability at 90°·s⁻¹ and computed a Fatigue Index (FI) as the percent change between the first and last five repetitions for peak torque (PT), work per repetition (J/rep), MNF, and RMS. Thirty-one healthy adults (21 men, 10 women; 22–35 y) completed 30 concentric knee extensions while torque and surface EMG were recorded. Force-related FI showed large declines (PT −33.5%; J/rep −34.3%) and MNF decreased by 20.1% (all p<0.001). RMS was unchanged overall (FI −5.7%, p=0.88) but rose in women (FI −17.4%) versus men (−0.08%; p=0.015). Under strength-oriented loading, FI provides a concise within-muscle metric linking reductions in force with neuromuscular activation and reveals a sex-specific RMS response. We propose adding FI-based isokinetic testing to established anaerobic assessments (Wingate, vertical jump) to enrich athlete monitoring and rehabilitation profiling. Larger cohorts are required to confirm these findings and clarify mechanisms underlying the female-specific RMS increase. Health sciences/Health care Health sciences/Medical research Biological sciences/Physiology Anaerobic exercise/capacity Fatigue Index Isokinetic muscle contraction Surface electromyography Full Text Additional Declarations No competing interests reported. Supplementary Files Appendix1.docx Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-7501643","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":528148498,"identity":"45c061ba-d149-45a6-b13b-755a070e1076","order_by":0,"name":"Smadar 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muscle","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Anaerobic exercise/capacity, Fatigue Index, Isokinetic muscle contraction, Surface electromyography","lastPublishedDoi":"10.21203/rs.3.rs-7501643/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7501643/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMuscle performance declines with fatigue; EMG mean frequency (MNF) falls linearly with repetitions, whereas root mean square (RMS) shows inconsistent individual patterns. Prior knee-extension studies used high angular velocities (≈180°·s⁻¹), emphasizing explosive power rather than maximal strength. We evaluated strength-oriented fatigability at 90°·s⁻¹ and computed a Fatigue Index (FI) as the percent change between the first and last five repetitions for peak torque (PT), work per repetition (J/rep), MNF, and RMS. Thirty-one healthy adults (21 men, 10 women; 22–35 y) completed 30 concentric knee extensions while torque and surface EMG were recorded. Force-related FI showed large declines (PT −33.5%; J/rep −34.3%) and MNF decreased by 20.1% (all p\u0026lt;0.001). RMS was unchanged overall (FI −5.7%, p=0.88) but rose in women (FI −17.4%) versus men (−0.08%; p=0.015). Under strength-oriented loading, FI provides a concise within-muscle metric linking reductions in force with neuromuscular activation and reveals a sex-specific RMS response. 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