Selective activation of neuromuscular compartments within the human trapezius muscle

A Holtermann, K Roeleveld, P J Mork, C Grönlund, J S Karlsson, L L Andersen, H B Olsen, M K Zebis, G Sjøgaard, Karen Søgaard

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    Abstract

    Task-dependent differences in relative activity between "functional" subdivisions within human muscles are well documented. Contrary, independent voluntary control of anatomical subdivisions, termed neuromuscular compartments is not observed in human muscles. Therefore, the main aim of this study was to investigate whether subdivisions within the human trapezius can be independently activated by voluntary command using biofeedback guidance. Bipolar electromyographical electrodes were situated on four subdivisions of the trapezius muscle. The threshold for "active" and "rest" for each subdivision was set to >12% and <1.5% of the maximal electromyographical amplitude recorded during a maximal voluntary contraction. After 1h with biofeedback from each of the four trapezius subdivisions, 11 of 15 subjects learned selective activation of at least one of the four anatomical subdivisions of the trapezius muscle. All subjects managed to voluntarily activate the lower subdivisions independently from the upper subdivisions. Half of the subjects succeeded to voluntarily activate both upper subdivisions independently from the two lower subdivisions. These findings show that anatomical subdivisions of the human trapezius muscle can be independently activated by voluntary command, indicating neuromuscular compartmentalization of the trapezius muscle. The independent activation of the upper and lower subdivisions of the trapezius is in accordance with the selective innervation by the fine cranial and main branch of the accessory nerve to the upper and lower subdivisions. These findings provide new insight into motor control characteristics, learning possibilities, and function of the clinically relevant human trapezius muscle.

    Original languageEnglish
    JournalJournal of Electromyography & Kinesiology
    Volume19
    Issue number5
    Pages (from-to)896-902
    Number of pages7
    ISSN1050-6411
    DOIs
    Publication statusPublished - Oct 2009

    Keywords

    • Adult
    • Algorithms
    • Anisotropy
    • Computer Simulation
    • Electromyography
    • Female
    • Humans
    • Male
    • Models, Biological
    • Muscle Contraction
    • Muscle, Skeletal
    • Principal Component Analysis
    • Shoulder Joint
    • Stress, Mechanical

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