Academic Journal
Shortened muscle position enhances firing rates of higher-recruitment-threshold motor units during submaximal contraction in tibialis anterior muscle.
| Τίτλος: | Shortened muscle position enhances firing rates of higher-recruitment-threshold motor units during submaximal contraction in tibialis anterior muscle. |
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| Συγγραφείς: | Hirono T; Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.; Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan., Vieira TM; Laboratory for Engineering of the Neuromuscular System (LISiN), Department of Electronics and Telecommunication, Politecnico di Torino, Turin, Italy., Watanabe K; Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan. |
| Πηγή: | Journal of neurophysiology [J Neurophysiol] 2026 Jul 01; Vol. 136 (1), pp. 29-33. Date of Electronic Publication: 2026 Jun 05. |
| Τύπος έκδοσης: | Journal Article |
| Γλώσσα: | English |
| Στοιχεία περιοδικού: | Publisher: American Physiological Society Country of Publication: United States NLM ID: 0375404 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1522-1598 (Electronic) Linking ISSN: 00223077 NLM ISO Abbreviation: J Neurophysiol Subsets: MEDLINE |
| Imprint Name(s): | Publication: Bethesda Md : American Physiological Society Original Publication: Washington [etc.] |
| Ιατρικοί όροι (MeSH): | Muscle, Skeletal*/physiology , Muscle, Skeletal*/innervation , Recruitment, Neurophysiological*/physiology , Motor Neurons*/physiology , Muscle Contraction* , Isometric Contraction*, Ankle Joint/physiology ; Humans ; Male ; Adult ; Female ; Electromyography ; Young Adult ; Torque ; Action Potentials |
| Περίληψη: | Voluntary force production depends on muscle-tendon unit length, due not only to mechanical factors (e.g., force-length properties and moment arms) but also neural modulation mediated by afferent feedback. Whether muscle length-dependent modulation of motor unit (MU) discharge differs across MU recruitment thresholds remains unclear. This study compared MU firing rates of the tibialis anterior during submaximal contractions with two ankle joint positions, while grouping MUs by recruitment threshold. Eighteen healthy adults performed isometric dorsiflexion at 0° (shortened position) and 20° (lengthened position) plantar flexion. High-density surface electromyography was decomposed into individual MU discharge times. Maximal voluntary contraction (MVC) torque was measured in each position. Participants then performed ramp-up contractions to 50% MVC. Firing rates were separately assessed for the same absolute target and relative MVC torque. MUs were categorized as low- (0%-15% MVC), mid- (15%-30% MVC), or high- (30%-45% MVC) threshold. High-threshold MUs discharged faster in the shortened than lengthened position under both absolute and relative torque comparisons, whereas low-threshold MU firing rates did not differ between positions. These findings indicate that a shortened muscle position preferentially enhances the firing rates of higher-threshold MUs during submaximal contractions, in agreement with neural compensation for reduced mechanical efficiency at shorter lengths.NEW & NOTEWORTHY High-density surface electromyography of the tibialis anterior was recorded during 50% of maximal torque with shortened and lengthened muscle positions. Motor units were divided into different groups, defined based on their recruitment threshold. A shortened muscle position enhanced the firing rate of motor units, especially those recruited at a higher threshold. The increase in firing rate of higher-threshold motor units may compensate for the disadvantage of force production due to the shortened muscle. |
| Grant Information: | 24K20528 MEXT | Japan Society for the Promotion of Science (JSPS) |
| Contributed Indexing: | Keywords: dorsiflexion; high-density surface electromyography; muscle length; optimal joint angle |
| Entry Date(s): | Date Created: 20260605 Date Completed: 20260623 Latest Revision: 20260623 |
| Update Code: | 20260623 |
| DOI: | 10.1152/jn.00163.2026 |
| PMID: | 42246439 |
| Βάση Δεδομένων: | MEDLINE |
| ISSN: | 1522-1598 |
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| DOI: | 10.1152/jn.00163.2026 |