Aging blunts hyperventilation-induced hypocapnia and reduction in cerebral blood flow velocity during maximal exercise

K R Marsden, M J Haykowsky, J D Smirl, M D Nelson, Luis A Altamirano-Diaz, J C Gelinas, Y C Tzeng, K J Smith, C K Willie, D M Bailey, Philip Ainslie, H Jones

Research output: Contribution to journalArticlepeer-review


Cerebral blood flow (CBF) increases from rest to ∼60% of peak oxygen uptake (VO(2peak)) and thereafter decreases towards baseline due to hyperventilation-induced hypocapnia and subsequent cerebral vasoconstriction. It is unknown what happens to CBF in older adults (OA), who experience a decline in CBF at rest coupled with a blunted ventilatory response during VO(2peak). In 14 OA (71 ± 10 year) and 21 young controls (YA; 23 ± 4 years), we hypothesized that OA would experience less hyperventilation-induced cerebral vasoconstriction and therefore an attenuated reduction in CBF at VO(2peak). Incremental exercise was performed on a cycle ergometer, whilst bilateral middle cerebral artery blood flow velocity (MCA V (mean); transcranial Doppler ultrasound), heart rate (HR; ECG) and end-tidal PCO(2) (P(ET)CO(2)) were monitored continuously. Blood pressure (BP) was monitored intermittently. From rest to 50% of VO(2peak), despite greater elevations in BP in OA, the change in MCA V(mean) was greater in YA compared to OA (28% vs. 15%, respectively; P < 0.0005). In the YA, at intensities >70% of VO(2peak), the hyperventilation-induced declines in both P(ET)CO(2) (14 mmHg (YA) vs. 4 mmHg (OA); P < 0.05) and MCA V(mean) (-21% (YA) vs. -7% (OA); P < 0.0005) were greater in YA compared to OA. Our findings show (1), from rest-to-mild intensity exercise (50% VO(2peak)), elevations in CBF are reduced in OA and (2) age-related declines in hyperventilation during maximal exercise result in less hypocapnic-induced cerebral vasoconstriction.

Original languageEnglish
Pages (from-to)725-35
Number of pages11
Issue number3
Publication statusPublished - Jun 2012


  • Adolescent
  • Adult
  • Aged
  • Aging
  • Cerebrovascular Circulation
  • Humans
  • Hyperventilation
  • Hypocapnia
  • Male
  • Middle Aged
  • Middle Cerebral Artery
  • Physical Exertion
  • Regional Blood Flow
  • Ultrasonography, Doppler, Transcranial
  • Vasoconstriction
  • Young Adult
  • Comparative Study


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