Document Detail

Effects of body position on the ventilatory response following an impulse exercise in humans.
MedLine Citation:
PMID:  11896006     Owner:  NLM     Status:  MEDLINE    
The aim of this study was to identify some of the mechanisms that could be involved in blunted ventilatory response (VE) to exercise in the supine (S) position. The contribution of the recruitment of different muscle groups, the activity of the cardiac mechanoreceptors, the level of arterial baroreceptor stimulation, and the hemodynamic effects of gravity on the exercising muscles was analyzed during upright (U) and S exercise. Delayed rise in VE and pulmonary gas exchange following an impulselike change in work rate (supramaximal leg cycling at 240 W for 12 s) was measured in seven healthy subjects and six heart transplant patients both in U and S positions. This approach allows study of the relationship between the rise in VE and O2 uptake (VO2) without the confounding effects of contractions of different muscle groups. These responses were compared with those triggered by an impulselike change in work rate produced by the arms, which were positioned at the same level as the heart in S and U positions to separate effects of gravity on postexercising muscles from those on the rest of the body. Despite superimposable VO2 and CO2 output responses, the delayed VE response after leg exercise was significantly lower in the S posture than in the U position for each control subject and cardiac-transplant patient (-2.58 +/- 0.44 l and -3.52 +/- 1.11 l/min, respectively). In contrast, when impulse exercise was performed with the arms, reduction of ventilatory response in the S posture reached, at best, one-third of the deficit after leg exercise and was always associated with a reduction in VO2 of a similar magnitude. We concluded that reduction in VE response to exercise in the S position is independent of the types (groups) of muscles recruited and is not critically dependent on afferent signals originating from the heart but seems to rely on some of the effects of gravity on postexercising muscles.
Philippe Haouzi; Bruno Chenuel; Bernard Chalon
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  92     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2002 Apr 
Date Detail:
Created Date:  2002-03-15     Completed Date:  2002-07-08     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:  1423-33     Citation Subset:  IM    
Laboratoire de Physiologie, Faculté de Médecine de Nancy, 54505 Vandouvre lès Nancy, France.
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MeSH Terms
Arm / physiology
Baroreflex / physiology
Blood Pressure / physiology
Exercise / physiology*
Heart Rate / physiology
Heart Transplantation
Leg / physiology
Mechanoreceptors / physiology
Middle Aged
Neurons, Afferent / physiology
Posture / physiology*
Pulmonary Ventilation / physiology*
Respiratory Mechanics / physiology*
Vasodilation / physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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