The dynamic response to a stimulus such as exercise can reveal valuable insights into systems control in health and disease that is not evident from the steady-state perturbation. However, the dynamic response profile and kinetics of cerebrovascular function have not been determined to date. We tested the hypotheses that bilateral middle cerebral artery blood flow velocity (MCAV) increases exponentially following the onset of moderate intensity exercise in ten healthy young subjects. The MCAV response profiles were well fit to a delay (TD) + exponential (time constant, τ) model with substantial agreement for baseline (L: 69, R: 64 cm·s-1, coefficient of variation, c.v. 11%), response amplitude (L: 16, R: 13 cm·s-1, c.v. 23%), TD (L: 54, R: 52 s, c.v. 9%), τ (L: 30, R: 30 s, c.v. 22%), and mean response time (MRT) (L: 83, R: 82 s, c.v. 8%) between left and right MCAV as supported by the high correlations (e.g., MRT r=0.82, P<0.05) and low c.v.'s. These responses contrasted markedly with that of a healthy older subject in whom the MCAV baseline and exercise response amplitude were far lower and the kinetics slowed. A single older stroke patient evinced baseline ipsilateral MCAV that was lower still and devoid of any exercise response whatsoever. We conclude that kinetics analysis of MCAV during exercise has significant potential to unveil novel aspects of cerebrovascular function in health and disease.
- brain blood flow
- middle cerebral artery
- blood flow velocity
- Copyright © 2016, Journal of Applied Physiology