Abstract
Cerebral blood flow (CBF) changes in response to exercise are intensity dependent, but it is unclear how well cerebral autoregulation (CA) is maintained at higher intensities. We had ten healthy subjects perform cycle exercise at 50%, 85%, and 115% of their ventilatory threshold (Vt) as well as delta 90 for a 5 minute bout. CBF (transcranial Doppler), mean arterial pressure (MAP), heart rate and ventilatory response were measured continuously throughout, and exercise responses were compared to baseline values. CA was calculated via transfer‐function (0.04 – 0.5 Hz) gain between MAP and mean CBF velocity and analyzed via repeated measures ANOVA. CBF and MAP significantly increased from baseline (59.24±5.3 cm/s, 90.6±6.4 mmHg) to exercise (64.83±5.8 cm/s, 103.81±6.3 mmHg). We observed minimal changes in gain during submaximal intensities (i.e. 50–115%Vt), but saw a significant decrease in gain from baseline (1.57±0.28) to exercise (0.63±0.23) as intensity increased (i.e. delta90). We interpret this significant interaction (baseline/exercise x intensity) as evidence of improved CA during high‐intensity exercise. Therefore, during high levels of exercise CBF is adequately maintained despite greater effort and increased cerebral metabolism.
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