Cerebral Blood Flow Velocity and Cognitive Function Preceding Post‐Exercise Syncope

Abstract

Adequate cerebral perfusion is necessary to maintain consciousness in the upright human. Following maximal anaerobic exercise, cerebral perfusion can become compromised as evident by post‐exercise syncope. It is unknown whether post‐exercise reductions in cerebral perfusion after exercise lead to cognitive deficits prior to the onset of syncope, which would be of utmost concern in populations such as emergency workers and soldiers. Therefore, the purpose of this experiment was to determine if reductions in cerebral blood flow velocity induced by maximal anaerobic exercise and head up tilt lead to visual/cognitive deficits prior to the onset of syncope. We hypothesized that a modified Wingate test followed by a head‐up tilt would reduce cerebral blood flow velocity and result in visual/cognitive deficits prior to the onset of syncope. Ten recreationally active volunteers were subjected to a symptom‐limited 60° head‐up tilt for up to 16 min before and after a 60‐s Wingate test. Blood flow velocity of the middle cerebral artery was measured via transcranial Doppler ultrasound and a visual decision‐reaction time test was assessed in the peripheral visual field. Cerebral blood flow velocity decreased as tilt progressed from 49.6 ± 3.2 to 46.2 ± 2.4 cm/s (mean ± SE; p < 0.05). Also, peripheral decision‐reaction time increased as tilt progressed from 363.7 ± 12.7 to 385.3 ± 18.4 ms (p < 0.05). These data suggest that the reduction in cerebral blood flow velocity following maximal anaerobic exercise contributes to cognitive deficits as evidenced by the concurrent increase in peripheral field decision‐reaction time prior to syncope.Support provided by NIH grant HL115027