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 lead to cognitive deficits prior to the onset of syncope, which would be of utmost concern in populations such as emergency workers and soldiers. PURPOSE: 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. METHODS: 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. All measures were analyzed using independent T-tests with a significance value set at p<0.05. RESULTS: 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). CONCLUSION: 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.

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