Journal of Applied Physiology

Cerebral blood flow during submaximal and maximal dynamic exercise in humans

S. N. Thomas, T. Schroeder, N. H. Secher, J. H. Mitchell


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.