Cerebral blood flow during submaximal and maximal dynamic exercise in humans.
Cerebral blood flow (CBF) in humans was measured at rest and during dynamic exercise on a cycle ergometer corresponding to 56% (range 27-85) of maximal O2 uptake (VO2max). Exercise bouts were performed by 16 male and female subjects, lasted 15 min each, and were carried out in a semisupine position. CBF (133Xe clearance) was expressed as the initial slope index (ISI) and as the first compartment flow (F1). CBF at rest [ISI, 58 (range 45-73); F1, 76 (range 55-98) ml.100 g-1.min-1] increased during exercise [ISI to 79 (57-94) and F1 to 118 (75-164) ml.100 g-1.min-1, P less than 0.01]. CBF did not differ significantly between work loads from 32 (24-33) to 86% (74-96) of VO2max (n = 10). During exercise, mean arterial pressure increased from 84 (60-100) to 101 (78-124) Torr (P less than 0.01) and PCO2 remained unchanged [5.1 (4.6-5.6) vs. 5.4 (4.4-6.3) kPa, n = 6]. These results demonstrate a median increase of 31% (0-87) in CBF by ISI and a median increase of 58% (0-133) in CBF by F1 during dynamic exercise in humans.
Thomas
S N
SN
Department of Anesthesia, Rigshospitalet, University of Copenhagen, Denmark.
Schroeder
T
T
Secher
N H
NH
Mitchell
J H
JH
D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002245:Carbon Dioxide; D002560:Cerebrovascular Circulation; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010313:Partial Pressure; D012119:Respiration; D013990:Tidal Volume
D002245:Carbon Dioxide