Effect of exercise on cerebral circulation.

The effect of supine physical exercise on cerebral blood flow (CBF) was measured in 30 normal subjects with the 133Xe inhalation technique. The CBF measurements were correlated to changes in PCO2, heart rate, and blood pressure, and to cardiac output and right atrial pressure in 10 of the subjects who underwent Swan-Ganz catheterization. No significant change was found in CBF during physical exercise, although a marked increase in cardiac output, blood pressure, and right atrial pressure and a mild decrease in PCO2 were found. Cerebrovascular resistance increased by 38%, in contrast to a decrease of 33% in the peripheral vascular resistance. The factors that affect the mechanism of cerebrovascular autoregulation during exercise are discussed.