Blood flow velocity waveforms in the middle cerebral artery at rest and during exercise

Blood flow velocities in the middle cerebral artery (MCA) were measured under steady-state and incremental cycle exercises using a transcranial Doppler ultrasound velocimeter. The peak systolic velocity was found to rise markedly under exercise, while the end diastolic velocity tended to remain at the resting value. The relationship between peak systolic velocity and systolic blood pressure, and that between peak systolic velocity and heart rate were found to show a statistically significant correlation. The mean MCA blood velocity also showed a significant correlation with the mean arterial pressure and heart rate. The fluctuations of velocity and the resistance index were calculated in order to evaluate the hemodynamic load on the vessel wall; these also increased markedly under exercise. Such hemodynamic changes in activity might be important in understanding the genesis of vascular diseases, as well as the physiology of cerebral circulation. © 2011 International Symposium on Artificial Life and Robotics (ISAROB).