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This Article Full Text Full Text (PDF) All Versions of this Article: 586/1/107    most recent jphysiol.2007.142273v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Volianitis, S. Articles by Nielsen, H. B. Search for Related Content PubMed PubMed Citation Articles by Volianitis, S. Articles by Nielsen, H. B. Related Collections Integrative

¹ Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, UK
² Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
³ Copenhagen Muscle Research Centre, Department of Anaesthesia, Rigshospitalet, Copenhagen, Denmark
⁴ Department of Medical Physiology, the Panum Institute, University of Copenhagen, Copenhagen, Denmark

Intense exercise decreases the cerebral metabolic ratio of O₂ to carbohydrates (glucose + lactate) and the cerebral lactate uptake depends on its arterial concentration, but whether these variables are influenced by O₂ availability is not known. In six males, maximal ergometer rowing increased the arterial lactate to 21.4 ± 0.8 mM (mean ± S.E.M.) and arterial–jugular venous (a–v) difference from –0.03 ± 0.01 mM at rest to 2.52 ± 0.03 mM (P < 0.05). Arterial glucose was raised to 8.5 ± 0.5 mM and its a–v difference increased from 1.03 ± 0.01 to 1.86 ± 0.02 mM (P < 0.05) in the immediate recovery. During exercise, the cerebral metabolic ratio decreased from 5.67 ± 0.52 at rest to 1.70 ± 0.23 (P < 0.05) and remained low in the early recovery. Arterial haemoglobin O₂ saturation was 92.5 ± 0.2% during exercise with room air, and it reached 87.6 ± 1.0% and 98.9 ± 0.2% during exercise with an inspired O₂ fraction of 0.17 and 0.30, respectively. Whilst the increase in a–v lactate difference was attenuated by manipulation of cerebral O₂ availability, the cerebral metabolic ratio was not affected significantly. During maximal rowing, the cerebral metabolic ratio reaches the lowest value with no effect by a moderate change in the arterial O₂ content. These findings suggest that intense whole body exercise is associated with marked imbalance in the cerebral metabolic substrate preferences independent of oxygen availability.

(Received 1 August 2007; accepted after revision 24 September 2007; first published online 11 October 2007)
Corresponding author S. Volianitis: Department of Health Science and Technology, Aalborg University, Denmark Fredrik Bajers Vej 7E4, DK-9220 Aalborg, Denmark. Email: svolian{at}hst.aau.dk

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