title: Dynamic cerebral autoregulation remains stable during physical challenge in healthy persons.
abstract: The effects of physical activity on cerebral blood flow (CBF) and cerebral autoregulation (CA) have not yet been fully evaluated. There is controversy as to whether increasing heart rate (HR), blood pressure (BP), and sympathetic and metabolic activity with altered levels of CO2 might compromise CBF and CA. To evaluate these effects, we studied middle cerebral artery blood flow velocity (CBFV) and CA in 40 healthy young adults at rest and during increasing levels of physical exercise. We continuously monitored HR, BP, end-expiratory CO2, and CBFV with transcranial Doppler sonography at rest and during stepwise ergometric challenge at 50, 100, and 150 W. The modulation of BP and CBFV in the low-frequency (LF) range (0.04-0.14 Hz) was calculated with an autoregression algorithm. CA was evaluated by calculating the phase shift angle and gain between BP and CBFV oscillations in the LF range. The LF BP-CBFV gain was then normalized by conductance. Cerebrovascular resistance (CVR) was calculated as mean BP adjusted to brain level divided by mean CBFV. HR, BP, CO2, and CBFV increased significantly with exercise. Phase shift angle, absolute and normalized LF BP-CBFV gain, and CVR, however, remained stable. Stable phase shift, LF BP-CBFV gain, and CVR demonstrate that progressive physical exercise does not alter CA despite increasing HR, BP, and CO2. CA seems to compensate for the hemodynamic effects and increasing CO2 levels during exercise.
authors.affiliation: Department of Neurology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.
authors.forename: Miroslaw
authors.initials: M
authors.lastname: Brys
authors.forename: Clive M
authors.initials: CM
authors.lastname: Brown
authors.forename: Harald
authors.initials: H
authors.lastname: Marthol
authors.forename: Renate
authors.initials: R
authors.lastname: Franta
authors.forename: Max J
authors.initials: MJ
authors.lastname: Hilz
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D010507:Periodicity; D005082:Physical Exertion / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology