Passive and active exercises increase cerebral blood flow velocity in young, healthy individuals

Unlike the well-examined cardiovascular changes during movement stimuli, changes of cerebral hemodynamics and cerebral metabolism in physical exercises have, as yet, rarely been studied. Our objective was to investigate whether there are changes in cerebral hemodynamics and cerebral metabolism caused by active and passive movement stimuli. Response to repetitive active and passive movement stimuli was studied in 14 volunteers (8 females, 6 males; mean age, 35.2+/-8 yr). Each volunteer was subjected to four measurement series while performing a defined active and passive exercise program of the right upper or right lower limb. Measurement series were designed according to Aaslid's "evoked flow test"; exercises were performed for 20 s, followed by a rest of 20 s. This sequence was repeated 10 times in each series. As a measure of cerebral hemodynamics mean and peak blood flow velocity of the middle cerebral artery were recorded by transcranial Doppler sonography (Multidop-X-DWL). In addition, cerebral metabolism was quantified in a subsample by means of oxygenic cytochrome aa3 (respiratory chain enzyme), cerebral oxygen saturation using near infrared spectroscopy (Critikon). As well, noninvasive blood pressure (Penaz method) and expiratory pCO2 were measured. Compared with resting measures, an increase in mean cerebral blood flow velocity of the middle cerebral artery of 3.8% (P = 0.003, paired t test) was observed after active exercises of the right lower limb and 3.5% after active exercises of the right upper limb. Respective changes were 3.4% (P = 0.004) for passive exercises of the lower limb and 4.6% (P = 0.007) for passive exercises of the right upper limb. Peak cerebral blood flow velocity of the middle cerebral artery showed an even more pronounced increase during passive and active exercises in all cases, with values of between 12.2% (P < 0.001) and 13.6% (P < 0.001). Significant increases (1.5-3%) of cytochrome aa3 and cerebral oxygen saturation were observed during active and passive exercises. These studies show that active as well as passive exercises are followed by an increase of cerebral blood flow velocity. We attribute the increase of cerebral hemodynamic and cerebral metabolism to cerebral activation and autoregulative mechanisms.