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Effects of exercise intensity on anterior cerebral perfusion in prepubertal children

University of British Columbia

Introduction: Although high intensity interval exercise (HIIE) has been well characterized in adults as providing superior systemic vascular adaptions compared to moderate intensity exercise (MIE), there is evidence that HIIE poses a challenge to cerebral hemodynamics. Only one study has investigated the child’s middle cerebral artery (MCA) response to incremental exercise to maximum, and we do not currently understand the cerebrovascular response to either HIIE or continuous MIE in the child. Methods: Nine children (aged 7-11 y; 5 girls) completed either HIIE (six 1-minute cycle ergometer sprints at 90% peak power (Wmax) with 1-minute recovery at 20% Wmax) or MIE (15 minutes at 44% Wmax on a cycle ergometer, matched to HIIE for external work). MCA velocity (MCAv), partial pressure of end tidal carbon dioxide (PETCO₂) and mean arterial pressure (MAP) were measured at baseline, immediately post-, 30 minutes post- and 60 minutes post-exercise. MCAv was also continuously recorded throughout exercise. A repeated measures ANOVA was used to compare changes from baseline across the time-points and between the exercise conditions. Results: The MCAv peaked during the first two minutes in both HIIE (minute 1: +12.10±2.70% & minute 2: +12.65±6.20%; p’s<0.05) and MIE (minute 1: +7.46±5.37% & minute 2: +9.78±6.40%; p’s<0.05). In HIIE, MCAv significantly decreased below baseline for the final 3 sprints (P<0.05), oscillating back to baseline for the remaining rest intervals. In MIE, the MCAv returned to baseline after the 4th minute of exercise, where it remained under exercise cessation. The cerebrovascular resistance index (CVRi) significantly increased (P’s<0.05) during the final minute of both MIE (+7.0±6.70%) and HIIE (+21.5±7.60%), with a significant difference between intensities (P<0.05). Immediately post HIIE, the MCAv uncoupled from PETCO₂, whereas immediately post MIE the MCAv and PETCO₂ remained at baseline values. Discussion: The decline in MCAv during the latter half of both HIIE and MIE may reflect adequate cerebral oxygenation because of the elevated MCAv baseline values in children compared to adults. The increase in CVRi in the final minute of HIIE is likely driven via hyperventilatory hypocapnia. Finally, it appears that PETCO₂ has a diminished regulatory effect over MCAv in children following HIIE.

Text

2017-11-27

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/63737

Interdisciplinary Studies

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/