DYNAMIC EXERCISE ENHANCES REGIONAL CEREBRAL-ARTERY MEAN FLOW VELOCITY

Anterior (ACA) and middle (MCA) cerebral artery mean flow velocities ( V-mean) and pulsatility indexes were determined using transcranial Dop pler in 14 subjects during dynamic exercise after assessment of the ca rbon dioxide reactivity for both arteries. Right hand contractions pro voked an elevation in left MCA V-mean [19% (12-28); P < 0.01], whereas the pulsatility decreased in all four arteries (P < 0.05). During rig ht foot movement, left ACA V-mean increased by 23% (11-37; P < 0.01) w ith lesser (similar to 10%; P < 0.05) increases in the other arteries, and pulsatility index decreased (P < 0.05). During cycling, ACA and M CA V-mean increased bilaterally by 23% (10-49) and 18% (5-32), respect ively (P < 0.01), and the pulsatility was also elevated (P < 0.05). Ce rebral artery pulsatility did not demonstrate a focal response but dep ended on the muscle mass involved during exercise. The data demonstrat e a significant increase in V-mean for the artery supplying the cortic al projection of the exercising limb. Insignificant and marginally sig nificant increases in V-mean may be related to sympathetically mediate d vasoconstriction and/or coactivation of untargeted muscle groups.