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This Article Full Text Full Text (PDF) All Versions of this Article: 107/3/741    most recent 91320.2008v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Legrand, A. Articles by Gevenois, P. A. PubMed PubMed Citation Articles by Legrand, A. Articles by Gevenois, P. A.

Neuromechanical matching of drive in the scalene muscle of the anesthetized rabbit

¹Department of Physiology and Pharmacology, University of Mons, Mons, Belgium; and ²Department of Radiology, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium

Submitted 1 October 2008 ; accepted in final form 10 July 2009

The scalene is a primary respiratory muscle in humans; however, in dogs, EMG activity recorded from this muscle during inspiration was reported to derive from underlying muscles. In the present studies, origin of the activity in the medial scalene was tested in rabbits, and its distribution was compared with the muscle mechanical advantage. We assessed in anesthetized rabbits the presence of EMG activity in the scalene, sternomastoid, and parasternal intercostal muscles during quiet breathing and under resistive loading, before and after denervation of the scalene and after its additional insulation. At rest, activity was always recorded in the parasternal muscle and in the scalene bundle inserting on the third rib (medial scalene). The majority of this activity disappeared after denervation. In the bundle inserting on the fifth rib (lateral scalene), the activity was inconsistent, and a high percentage of this activity persisted after denervation but disappeared after insulation from underlying muscle layers. The sternomastoid was always silent. The fractional change in muscle length during passive inflation was then measured. The mean shortening obtained for medial and lateral scalene and parasternal intercostal was 8.0 ± 0.7%, 5.5 ± 0.5%, and 9.6 ± 0.1%, respectively, of the length at functional residual capacity. Sternomastoid muscle length did not change significantly with lung inflation. We conclude that, similar to that shown in humans, respiratory activity arises from scalene muscles in rabbits. This activity is however not uniformly distributed, and a neuromechanical matching of drive is observed, so that the most effective part is also the most active.

electromyographic activity; neck muscle; mechanics of breathing