title: Anterior cerebral blood velocity and end-tidal CO2responses to exercise differ in children and adults.
abstract: 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([Formula: see text]), blood pressure, and minute ventilation (V̇e) 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, [Formula: see text], and V̇e were measured continuously. These variables were measured at rest, at exercise intensities specific to individual ventilatory thresholds, and at maximum. Although MCAVmeanwas 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 [Formula: see text] with exercise intensity in an age-dependent manner [F(2.5,54.5) = 7.983,P< 0.001; η2= 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, [Formula: see text] 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 MCAVmeanduring exercise was attenuated in children compared with adults. There was also a weaker relationship between MCAVmeanand [Formula: see text] during exercise in children, suggesting that cerebral perfusion may be regulated by different mechanisms during exercise in the child.NEW & NOTEWORTHYThese findings provide the first direct evidence that exercise increases cerebral blood flow in children to a lesser extent than in adults. Changes in end-tidal CO2parallel changes in cerebral perfusion in adults but not in children, suggesting age-dependent regulatory mechanisms of cerebral blood flow during exercise.
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada.
authors.forename: Lindsay A
authors.initials: LA
authors.lastname: Ellis
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada.
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada.
authors.forename: Victoria A
authors.initials: VA
authors.lastname: Armstrong
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Morris
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada.
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Simair
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada.
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Sletten
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Tallon
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada ali.mcmanus@ubc.ca.
authors.forename: Ali M
authors.identifier: http://orcid.org/0000-0002-7817-230X
authors.initials: AM
authors.lastname: McManus
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000367:Age Factors; D015415:Biomarkers / Q000097:blood; D001783:Blood Flow Velocity; D002245:Carbon Dioxide / Q000097:blood*; D002560:Cerebrovascular Circulation; D002648:Child; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000097:blood / Q000503:physiopathology*; D016857:Hypocapnia / Q000097:blood / Q000503:physiopathology*; D008297:Male; D020768:Middle Cerebral Artery / Q000503:physiopathology*; D012123:Pulmonary Ventilation; D012039:Regional Blood Flow; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; D002245:Carbon Dioxide
keywords: cerebral blood flow; children; exercise; growth and development; ventilation