Document Detail

Effect of blood haemoglobin concentration on V(O2,max) and cardiovascular function in lowlanders acclimatised to 5260 m.
MedLine Citation:
PMID:  12456846     Owner:  NLM     Status:  MEDLINE    
The principal aim of this investigation was to determine the influence of blood haemoglobin concentration ([Hb]) on maximal exercise capacity and maximal O(2) consumption (V(O(2),max)) in healthy subjects acclimatised to high altitude. Secondarily, we examined the effects of [Hb] on the regulation of cardiac output (CO), blood pressure and muscular blood flow (LBF) during exercise. Eight Danish lowlanders (three females and five males; 24 +/- 0.6 years, mean +/- S.E.M.) performed submaximal and maximal exercise on a cycle ergometer after 9 weeks at an altitude of 5260 m (Mt Chacaltaya, Bolivia). This was done first with the high [Hb] resulting from acclimatisation and again 2-4 days later, 1 h after isovolaemic haemodilution with Dextran 70 to near sea level [Hb]. After measurements at maximal exercise while breathing air at each [Hb], subjects were switched to hyperoxia (55 % O(2) in N(2)) and the measurements were repeated, increasing the work rate as tolerated. Hyperoxia increased maximal power output and leg V(O(2),max), showing that breathing ambient air at 5260 m, V(O(2),max) is limited by the availability of O(2) rather than by muscular oxidative capacity. Altitude increased [Hb] by 36 % from 136 +/- 5 to 185 +/- 5 g l(-1) (P < 0.001), while haemodilution (replacing 1 l of blood with 1 l of 6 % Dextran) lowered [Hb] by 24 % to 142 +/- 6 g l(-1) (P < 0.001). Haemodilution had no effect on maximal pulmonary or leg V(O(2),max), or power output. Despite higher LBF, leg O(2) delivery was reduced and maximal V(O(2)) was thus maintained by higher O(2) extraction. While CO increased linearly with work rate irrespective of [Hb] or inspired oxygen fraction (F(I,O(2))), both LBF and leg vascular conductance were systematically higher when [Hb] was low. Close and significant relationships were seen between LBF (and CO) and both plasma noradrenaline and K(+) concentrations, independently of [Hb] and F(I,O(2)). In summary, under conditions where O(2) supply limits maximal exercise, the increase in [Hb] with altitude acclimatisation does not improve maximal exercise capacity or V(O(2),max), and does not alter peak CO. However, LBF and vascular conductance are higher at altitude when [Hb] is lowered to sea level values, with both relating closely to catecholamine and potassium concentrations. This suggests that the lack of effect of [Hb] on V(O(2),max) may involve reciprocal changes in LBF via local metabolic control of the muscle vasculature.
J A L Calbet; G Rådegran; R Boushel; H Søndergaard; B Saltin; P D Wagner
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of physiology     Volume:  545     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2002 Dec 
Date Detail:
Created Date:  2002-11-28     Completed Date:  2003-06-16     Revised Date:  2013-06-09    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  715-28     Citation Subset:  IM    
Department of Physical Education, University of Las Palmas de Gran Canaria, Spain, and The Copenhagen Muscle Research Centre, Rigshospitalet, 2200 Copenhagen N, Denmark.
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MeSH Terms
Acclimatization / physiology*
Anaerobic Threshold / physiology*
Blood Gas Analysis
Blood Pressure / physiology
Cardiac Output / physiology
Catecholamines / blood
Exercise / physiology
Heart Rate / physiology
Hemodynamics / physiology*
Hemoglobins / physiology*
Lactic Acid / blood
Oxygen Consumption / physiology*
Potassium / blood
Regional Blood Flow / physiology
Respiratory Mechanics / physiology
Stroke Volume / physiology
Reg. No./Substance:
0/Catecholamines; 0/Hemoglobins; 50-21-5/Lactic Acid; 7440-09-7/Potassium

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