Interaction between postural and respiratory control of human intercostal muscles. Rimmer, K. P., G. T. Ford, and W. A. Whitelaw. Department of Medicine, University of Calgary, Calgary, Alberta, Canada
APStracts 2:0294A, 1995.
To study the interaction between postural and respiratory control of intercostal muscles, we used electromyography of intercostal muscles of the lateral chest wall in conscious humans. Bipolar fine wire electrodes were placed in external and internal intercostal muscles in the midaxillary line of 4 subjects who sat on a bench and breathed through a pneumotachograph. They were instructed to hold their breath at end expiration, rotate their thorax to the right or left, and then hold the rotation while resuming breathing. Holding a rotation induces steady tonic activity in either internal or external intercostal muscles, depending on the direction of the rotation. The degree of rotation was varied from one run to the next resulting in varied levels of tonic postural activity. When breathing resumes, internal intercostal muscles have their activity almost completely suppressed with each inspiration independently of whether the tonic postural tone is small or large. External intercostal muscles show inspiratory increases in activity superimposed on the postural tone, which apparently amplifies the effect of respiratory input to their motorneurons. 

Received 25 October 1994; accepted in final form 21 June 1995.
APS Manuscript Number A1099-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.