Research article summary:

External perturbation of the trunk in standing humans differentially activates components of the medial back muscles.

Abstract Extract:
During voluntary arm movements, the medial back muscles are differentially active. It is not known whether differential activity also occurs when the trunk is perturbed unpredictably, when the earliest responses are initiated by short-latency spinal ... (Full abstract text below)

Published 2003Mar in Journal: J Physiol (Language : eng)

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1. J Physiol. 2003 Mar;547(Pt 2):581-7

External perturbation of the trunk in standing humans differentially activates components of the medial back muscles.

Moseley GL, Hodges PW, Gandevia SC

Prince of Wales Medical Research Institute, Sydney, Australia.

During voluntary arm movements, the medial back muscles are differentially active. It is not known whether differential activity also occurs when the trunk is perturbed unpredictably, when the earliest responses are initiated by short-latency spinal mechanisms rather than voluntary commands. To assess this, in unpredictable and self-initiated conditions, a weight was dropped into a bucket that was held by the standing subject (n = 7). EMG activity was recorded from the deep (Deep MF), superficial (Sup MF) and lateral (Lat MF) lumbar multifidus, the thoracic erector spinae (ES) and the biceps brachii. With unpredictable perturbations, EMG activity was first noted in the biceps brachii, then the thoracic ES, followed synchronously in the components of the multifidus. During self-initiated perturbations, background EMG in the Deep MF increased two- to threefold, and the latency of the loading response decreased in six out of the seven subjects. In Sup MF and Lat MF, this increase in background EMG was not observed, and the latency of the loading response was increased. Short-latency reflex mechanisms do not cause differential action of the medial back muscles when the trunk is loaded. However, during voluntary tasks the central nervous system exerts a 'tuned response', which involves discrete activity in the deep and superficial components of the medial lumbar muscles in a way that varies according to the biomechanical action of the muscle component.

PMID : 12562944 [PubMed - Indexed for MEDLINE]

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Full Author Information

First Name	LastName	Initials
G Lorimer	Moseley	GL
Paul W	Hodges	PW
S C	Gandevia	SC

Affiliation: Prince of Wales Medical Research Institute, Sydney, Australia.

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