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Acute Modulation of Lumbar Motor Unit Behavior During Experimentally Induced Low Back Pain: A Motor Unit Decomposition Analysis.

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Τίτλος: Acute Modulation of Lumbar Motor Unit Behavior During Experimentally Induced Low Back Pain: A Motor Unit Decomposition Analysis.
Συγγραφείς: Parolini F; Northern School of Health, Portuguese Red Cross, Oliveira de Azeméis, Portugal.; Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal.; Center for Rehabilitation Research (CIR), ESS, Polytechnic of Porto, Porto, Portugal., Becker KM; Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal., Vilas-Boas JP; Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal., Ervilha UF; Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal.; Laboratory of Physical Activity Sciences, School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, Brazil., Santos R; Center for Rehabilitation Research (CIR), ESS, Polytechnic of Porto, Porto, Portugal., Goethel MF; Center of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal.
Πηγή: Physiotherapy research international : the journal for researchers and clinicians in physical therapy [Physiother Res Int] 2026 Jul; Vol. 31 (3), pp. e70278.
Τύπος έκδοσης: Journal Article
Γλώσσα: English
Στοιχεία περιοδικού: Publisher: John Wiley & Sons Country of Publication: United States NLM ID: 9612022 Publication Model: Print Cited Medium: Internet ISSN: 1471-2865 (Electronic) Linking ISSN: 13582267 NLM ISO Abbreviation: Physiother Res Int Subsets: MEDLINE
Imprint Name(s): Publication: 2006- : Hoboken, NJ : John Wiley & Sons
Original Publication: London ; Lawrence, KS : Whurr Publishers, c1996-
Ιατρικοί όροι (MeSH): Low Back Pain*/physiopathology , Recruitment, Neurophysiological*/physiology , Motor Neurons*/physiology , Muscle, Skeletal*/physiopathology, Action Potentials/physiology ; Muscle Contraction/physiology ; Humans ; Adult ; Female ; Male ; Young Adult ; Electromyography ; Saline Solution, Hypertonic ; Adolescent ; Pain Measurement ; Adaptation, Physiological
Περίληψη: Background and Purpose: Acute low back pain is a prevalent musculoskeletal disorder that can disrupt motor control and compromise functional stability. Evidence suggests that pain alters motor unit discharge characteristics and the temporal organization of muscle activation; however, the specific neuromuscular adaptations associated with acute low back pain remain insufficiently understood. This study aimed to investigate the effects of experimentally induced acute low back pain on force steadiness and motor unit discharge characteristics (including recruitment threshold, motor unit firing rate, and action potential amplitude) during a sustained spinal extension task METHODS: Thirty-three healthy participants (aged 18-40 years) performed a sustained spinal extension task at 20% of their maximum voluntary contraction under two experimental conditions: pre- and during pain induced by hypertonic saline injection, and pre- and during-isotonic saline injection into the right lumbar region. Electromyography signals were recorded bilaterally from the longissimus muscles. Signals were decomposed into individual motor unit action potential trains using advanced algorithms and clustered using the K-means method.
Results: The hypertonic saline injection successfully induced moderate pain on the numerical pain rating scale (NPRS) (median = 4.71; interquartile range (IQR) = 1.61), which was significantly higher than the isotonic control condition (NPRS median = 1.50; IQR = 1.00; p < 0.001). During the pain condition, significant lateralized adaptations were observed: motor units within the contralateral (left) longissimus muscle exhibited an increased firing rate (p = 0.020, r = 0.33), with no significant changes in the recruitment threshold or motor unit action potential amplitude. On the ipsilateral side, subtle modulations in recruitment threshold were detected. In contrast, the isotonic condition elicited only localized and nonsystemic neuromuscular changes, without the coordinated bilateral organization observed under acute pain.
Discussion: Acute low back pain induces a dynamic and lateralized modulation of motor unit recruitment, suggesting a compensatory redistribution of neural drive that may help preserve functional stability despite altered motor coordination. These findings provide novel insights into the neuromuscular adaptations underlying acute low back pain and have potential implications for physiotherapy assessment and intervention.
(© 2026 John Wiley & Sons Ltd.)
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Grant Information: UI/BD/151415 Rehabilitation Research Center-Foundation for Science and Technology through R&D Units; /2021 Rehabilitation Research Center-Foundation for Science and Technology through R&D Units
Contributed Indexing: Keywords: electromyography; force steadiness; isometric contraction; low back pain; motor units; neuromuscular adaptation
Substance Nomenclature: 0 (Saline Solution, Hypertonic)
Entry Date(s): Date Created: 20260711 Date Completed: 20260711 Latest Revision: 20260726
Update Code: 20260726
PubMed Central ID: PMC13355871
DOI: 10.1002/pri.70278
PMID: 42435379
Βάση Δεδομένων: MEDLINE
Περιγραφή
ISSN:1471-2865
DOI:10.1002/pri.70278