Regional activation in the human longissimus thoracis pars lumborum muscle

Abboud, J., Kuo, C., Descarreaux, M. et Blouin, J.-S. (2019). Regional activation in the human longissimus thoracis pars lumborum muscle. The Journal of Physiology, 598 (2). pp. 347-359. ISSN 0022-3751 1469-7793 DOI 10.1113/JP278260

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Résumé

Key points: Longissimus activity in the lumbar region was measured using indwelling electromyography to characterize the territory of its motor units. The distribution of motor units in the longissimus pars lumborum muscle was mainly grouped into two distinct regions. Regional activation of the longissimus pars lumborum was also observed during functional tasks involving trunk movements. The regional activation of the longissimus pars lumborum muscle may play a role in segmental stabilization of the lumbar spine. Abstract: The longissimus pars lumborum contributes to lumbar postural control and movement. While animal studies suggest a segmental control of this muscle, the territory of motor units constituting the human longissimus pars lumborum remains unknown. The aims of this study were to identify the localization of motor unit territories in the longissimus and assess the activation of this muscle during functional tasks. Eight healthy participants were recruited. During isometric back extension contractions, single motor-unit (at L1, L2, L3 and L4) and multi-unit indwelling recordings (at L1, L1-L2, L2, L2-L3, L3, L3-L4 and L4) were used to estimate motor unit territories in the longissimus pars lumborum based on the motor-unit spike-triggered averages from fine-wire electrodes. A series of functional tasks involving trunk and arm movements were also performed. A total of 73 distinct motor units were identified along the length of the longissimus: only two motor units spanned all recording sites. The majority of the recorded motor units had muscle fibers located in two main rostro-caudal territories (32 motor units spanned L1 to L3 and 30 spanned ?L3 to L4) and 11 had muscle fibers outside these two main territories. We also observed distinct muscle activation between the rostral and caudal regions of the longissimus pars lumborum during a trunk rotation task. Our results show clear rostral and caudal motor unit territories in the longissimus pars lumborum muscle and suggest that the central nervous system can selectively activate regions of the superficial lumbar muscles to provide local stabilization of the spine. This article is protected by copyright. All rights reserved

Type de document:	Article
Mots-clés libres:	erector spinae lumbar spine electromyography motor unit
Date de dépôt:	25 août 2021 14:05
Dernière modification:	25 août 2021 14:05
Version du document déposé:	Post-print (version corrigée et acceptée)
URI:	https://depot-e.uqtr.ca/id/eprint/9720

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