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

Unlike the well-examined cardiovascular changes during movement stimuli, ch anges of cerebral hemodynamics and cerebral metabolism in physical exercise s have, as yet, rarely been studied. Our objective was to investigate wheth er there are changes in cerebral hemodynamics and cerebral metabolism cause d by active and passive movement: stimuli. Response to repetitive active an d passive movement stimuli was studied in 14 volunteers (8 females, 6 males ; mean age, 35.2 +/- 8 yr). Each volunteer was subjected to four measuremen t series while performing a defined active and passive exercise program of the right upper or right lower limb. Measurement series were designed accor ding to Aaslid's "evoked flow test"; exercises were performed for 20 s, fol lowed 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 o f the middle cerebral artery were recorded by transcranial Doppler sonograp hy (Multidop-X-DWL), In addition, cerebral metabolism was quantified in a s ubsample by means of oxygenic cytochrome aa3 (respiratory chain enzyme), ce rebral oxygen saturation using near infrared spectroscopy (Critikon). As we ll, noninvasive blood pressure (Penaz method) and expiratory pCO(2) were me asured. 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 te st) was observed after active exercises of the right lower limb and 3.5% af ter 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) fo r passive exercises of the right upper limb. Peak cerebral blood flow veloc ity of the middle cerebral artery showed an even more pronounced increase d uring 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 cyt ochrome aa3 and cerebral oxygen saturation were observed during active and passive exercises. These studies show that active as well as passive exerci ses are followed by an increase of cerebral blood flow velocity. We attribu te the increase of cerebral hemodynamic and cerebral metabolism to cerebral activation and autoregulative mechanisms.