Anterior cerebral blood velocity and end-tidal CO2 responses to exercise differ in children and adults

Little is known about the response of the cerebrovasculature to acute exercise in children and how these responses might differ with adults. Therefore, we compared changes in middle cerebral artery blood velocity (MCAVmean), end-tidal Pco2 (PETCO2), blood pressure, and minute ventilation (Ve) in response to incremental exercise between children and adults. Thirteen children [age: 9 ± 1 (SD) yr] and thirteen sex-matched adults (age: 25 ± 4 yr) completed a maximal exercise test, during which MCAVmean, PETCO2, and Ve were measured continuously. These variables were measured at rest, at exercise intensities specific to individual ventilatory thresholds, and at maximum. Although MCAVmean was higher at rest in children compared with adults, there were smaller increases in children (1–12%) compared with adults (12–25%) at all exercise intensities. There were alterations in PETCO2 with exercise intensity in an age-dependent manner [F(2.5,54.5) = 7.983, P < 0.001; 2 = 0.266], remaining stable in children with increasing exercise intensity (37–39 mmHg; P > 0.05) until hyperventilation-induced reductions following the respiratory compensation point. In adults, PETCO2 increased with exercise intensity (36–45 mmHg, P < 0.05) until the ventilatory threshold. From the ventilatory threshold to maximum, adults showed a greater hyperventilation-induced hypocapnia than children. These findings show that the relative increase in MCAVmean during exer...
Source: AJP: Heart and Circulatory Physiology - Category: Cardiology Authors: Tags: RESEARCH ARTICLE Source Type: research