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

The blood flow velocities in the middle cerebral artery were measured under steady-state and incremental cycle exercises using the transcranial Doppler ultrasound velocimeter. The peak-systolic velocity was found to rise markedly under exercise, while the end-diastolic velocity tended to keep a resting value. The fluctuation of velocity and resistance index were calculated in order to evaluate the hemodynamic load on the vessel wall. They also increased markedly under exercise. Such hemodynamic changes in activity might be important in understanding the genesis of vascular diseases as well as physiology of cerebral circulation.