caa a22 4500 467940983 CHVBK 20180406153012.0 cr unu---uuuuu 170328e20060201xx s 000 0 eng 10.1007/s00421-005-0079-3 doi (NATIONALLICENCE)springer-10.1007/s00421-005-0079-3 Enhanced cerebral CO2 reactivity during strenuous exercise in man [Elektronische Daten] [P. Rasmussen, H. Stie, B. Nielsen, L. Nybo] Light and moderate exercise elevates the regional cerebral blood flow by ~20% as determined by ultrasound Doppler sonography (middle cerebral artery mean flow velocity; MCA V mean). However, strenuous exercise, especially in the heat, appears to reduce MCA V mean more than can be accounted for by the reduction in the arterial CO2 tension (P aCO2). This study evaluated whether the apparently large reduction in MCA V mean at the end of exhaustive exercise relates to an enhanced cerebrovascular CO2 reactivity. The CO2 reactivity was evaluated in six young healthy male subjects by the administration of CO2 as well as by voluntary hypo- and hyperventilation at rest and during exercise with and without hyperthermia. At rest, P aCO2 was 5.1±0.2kPa (mean±SEM) and MCA V mean 50.7±3.8cms−1 and the relationship between MCA V mean and P aCO2 was linear (double-log slope 1.1±0.1). However, the relationship became curvilinear during exercise (slope 1.8±0.1; P<0.01 vs. rest) and during exercise with hyperthermia (slope 2.3±0.3; P<0.05 vs. control exercise). Accordingly, the cerebral CO2 reactivity increased from 30.5±2.7%kPa−1 at rest to 61.4±10.1%kPa−1 during exercise with hyperthermia (P<0.05). At exhaustion P aCO2 decreased 1.1±0.2kPa during exercise with hyperthermia, which, with the determined cerebral CO2 reactivity, accounted for the 28±10% decrease in MCA V mean. The results suggest that during exercise changes in cerebral blood flow are dominated by the arterial carbon dioxide tension. Springer-Verlag, 2005 Arterial carbon dioxide tension nationallicence Cerebral blood flow nationallicence End tidal carbon dioxide tension nationallicence Hyperthermia nationallicence Transcranial Doppler nationallicence Rasmussen P. Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark aut Stie H. Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark aut Nielsen B. Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark aut Nybo L. Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark aut European Journal of Applied Physiology Springer-Verlag 96/3(2006-02-01), 299-304 1439-6319 96:3<299 2006 96 421 https://doi.org/10.1007/s00421-005-0079-3 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00421-005-0079-3 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rasmussen P. Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark aut NATIONALLICENCE 700 1- Stie H. Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark aut NATIONALLICENCE 700 1- Nielsen B. Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark aut NATIONALLICENCE 700 1- Nybo L. Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark aut NATIONALLICENCE 773 0- European Journal of Applied Physiology Springer-Verlag 96/3(2006-02-01), 299-304 1439-6319 96:3<299 2006 96 421 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer