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Dynamic cerebral autoregulation during exhaustive exercise in humans
Shigehiko Ogoh1, Mads K Dalsgaard, Chie C Yoshiga
1Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA. sogoh@hsc.unt.edu <sogoh@hsc.unt.edu>
American Journal of Physiology. Heart and Circulatory Physiology
|October 23, 2004
Summary
Exhaustive exercise impairs dynamic cerebral autoregulation, affecting blood flow regulation in the brain. This study shows reduced middle cerebral artery blood flow velocity despite stable mean arterial pressure during intense exercise.
Area of Science:
- Exercise Physiology
- Neuroscience
- Cardiovascular Physiology
Background:
- Dynamic cerebral autoregulation maintains stable brain blood flow during physiological stress.
- The impact of exhaustive exercise on cerebral blood flow regulation remains incompletely understood.
Purpose of the Study:
- To investigate the effects of exhaustive exercise on dynamic cerebral autoregulation.
- To assess changes in middle cerebral artery blood flow velocity and its relationship with mean arterial pressure oscillations.
Main Methods:
- Seven subjects underwent dynamic leg-cycle ergometry to exhaustion.
- Mean arterial pressure (MAP) and middle cerebral artery mean blood flow velocity (MCA V(mean)) were measured.
- Transfer-function analysis was used to assess dynamic cerebral autoregulation (gain and phase shift).
- Cerebral oxygen saturation (Sv(O(2))) and arterial Pco(2) (Pa(CO(2))) were monitored.
Main Results:
- Despite no significant change in MAP, MCA V(mean) decreased significantly during exhaustive exercise.
- Jugular venous oxygen saturation (Sv(O(2))) decreased, indicating altered brain oxygenation.
- The normalized low-frequency gain between MAP and MCA V(mean) increased, suggesting impaired autoregulation.
- A decrease in the cerebral metabolic ratio indicated an effect on brain metabolism.
Conclusions:
- Exhaustive exercise impairs dynamic cerebral autoregulation.
- Reduced middle cerebral artery blood flow velocity and altered transfer function gain suggest compromised brain blood flow regulation during intense physical exertion.
- These findings highlight the vulnerability of cerebral blood flow control during extreme exercise conditions.