| Influence of respiratory muscle work on VO(2) and leg blood flow during submaximal exercise. | |
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MedLine Citation:
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PMID: 10444624 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The work of breathing (W(b)) normally incurred during maximal exercise not only requires substantial cardiac output and O(2) consumption (VO(2)) but also causes vasoconstriction in locomotor muscles and compromises leg blood flow (Q(leg)). We wondered whether the W(b) normally incurred during submaximal exercise would also reduce Q(leg). Therefore, we investigated the effects of changing the W(b) on Q(leg) via thermodilution in 10 healthy trained male cyclists [maximal VO(2) (VO(2 max)) = 59 +/- 9 ml. kg(-1). min(-1)] during repeated bouts of cycle exercise at work rates corresponding to 50 and 75% of VO(2 max). Inspiratory muscle work was 1) reduced 40 +/- 6% via a proportional-assist ventilator, 2) not manipulated (control), or 3) increased 61 +/- 8% by addition of inspiratory resistive loads. Increasing the W(b) during submaximal exercise caused VO(2) to increase; decreasing the W(b) was associated with lower VO(2) (DeltaVO(2) = 0.12 and 0.21 l/min at 50 and 75% of VO(2 max), respectively, for approximately 100% change in W(b)). There were no significant changes in leg vascular resistance (LVR), norepinephrine spillover, arterial pressure, or Q(leg) when W(b) was reduced or increased. Why are LVR, norepinephrine spillover, and Q(leg) influenced by the W(b) at maximal but not submaximal exercise? We postulate that at submaximal work rates and ventilation rates the normal W(b) required makes insufficient demands for VO(2) and cardiac output to require any cardiovascular adjustment and is too small to activate sympathetic vasoconstrictor efferent output. Furthermore, even a 50-70% increase in W(b) during submaximal exercise, as might be encountered in conditions where ventilation rates and/or inspiratory flow resistive forces are higher than normal, also does not elicit changes in LVR or Q(leg). |
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Authors:
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T J Wetter; C A Harms; W B Nelson; D F Pegelow; J A Dempsey |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 87 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 1999 Aug |
Date Detail:
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Created Date: 1999-09-08 Completed Date: 1999-09-08 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 643-51 Citation Subset: IM |
Affiliation:
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John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin, Madison, Wisconsin 53705, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Blood Pressure Catecholamines / blood Exercise / physiology* Humans Leg / blood supply* Male Oxygen Consumption Regional Blood Flow Regression Analysis Respiration, Artificial Respiratory Function Tests Respiratory Muscles / physiology* Vascular Resistance / physiology Work of Breathing / physiology* |
| Grant Support | |
ID/Acronym/Agency:
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R01 HL-15469/HL/NHLBI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Catecholamines |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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