Document Detail

Human respiratory muscle actions and control during exercise.
MedLine Citation:
PMID:  9338435     Owner:  NLM     Status:  MEDLINE    
We measured pressures and power of diaphragm, rib cage, and abdominal muscles during quiet breathing (QB) and exercise at 0, 30, 50, and 70% maximum workload (Wmax) in five men. By three-dimensional tracking of 86 chest wall markers, we calculated the volumes of lung- and diaphragm-apposed rib cage compartments (Vrc,p and Vrc,a, respectively) and the abdomen (Vab). End-inspiratory lung volume increased with percentage of Wmax as a result of an increase in Vrc,p and Vrc,a. End-expiratory lung volume decreased as a result of a decrease in Vab. DeltaVrc,a/DeltaVab was constant and independent of Wmax. Thus we used DeltaVab/time as an index of diaphragm velocity of shortening. From QB to 70% Wmax, diaphragmatic pressure (Pdi) increased approximately 2-fold, diaphragm velocity of shortening 6.5-fold, and diaphragm workload 13-fold. Abdominal muscle pressure was approximately 0 during QB but was equal to and 180 degrees out of phase with rib cage muscle pressure at all percent Wmax. Rib cage muscle pressure and abdominal muscle pressure were greater than Pdi, but the ratios of these pressures were constant. There was a gradual inspiratory relaxation of abdominal muscles, causing abdominal pressure to fall, which minimized Pdi and decreased the expiratory action of the abdominal muscles on Vrc,a gradually, minimizing rib cage distortions. We conclude that from QB to 0% Wmax there is a switch in respiratory muscle control, with immediate recruitment of rib cage and abdominal muscles. Thereafter, a simple mechanism that increases drive equally to all three muscle groups, with drive to abdominal and rib cage muscles 180 degrees out of phase, allows the diaphragm to contract quasi-isotonically and act as a flow generator, while rib cage and abdominal muscles develop the pressures to displace the rib cage and abdomen, respectively. This acts to equalize the pressures acting on both rib cage compartments, minimizing rib cage distortion.
A Aliverti; S J Cala; R Duranti; G Ferrigno; C M Kenyon; A Pedotti; G Scano; P Sliwinski; P T Macklem; S Yan
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  83     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1997 Oct 
Date Detail:
Created Date:  1997-11-26     Completed Date:  1997-11-26     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1256-69     Citation Subset:  IM    
Politecnico di Milano, Dipartimento di Bioingegneria, Centro di Bioingegneria, Milan, Italy.
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MeSH Terms
Abdominal Muscles / anatomy & histology,  physiology
Area Under Curve
Diaphragm / anatomy & histology,  physiology
Exercise / physiology*
Lung Volume Measurements
Models, Anatomic
Muscle Contraction / physiology
Muscle Relaxation / physiology
Respiratory Mechanics / physiology
Respiratory Muscles / physiology*

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