Cognitive impairment during high-intensity exercise: influence of cerebral blood flow

Purpose: Cognitive performance appears to be impaired during high-intensity exercise, and this occurs concurrently with a reduction in cerebral blood flow (CBF). However, it is unclear whether cognitive impairment during high-intensity exercise is associated with reduced CBF. We tested the hypothesis that a reduction in CBF is responsible for impaired cognitive performance during high-intensity exercise.

Methods: Using a randomized crossover design seventeen healthy males performed spatial delayed-response (DR) and Go/No-Go tasks in three conditions [Exercise (EX), Exercise+CO₂ (EX+CO₂), and a non-exercising Control (CON)]. In the EX and EX+CO₂, they performed cognitive tasks at rest and during 8-mins of moderate and high-intensity exercise. Exercise intensity corresponded to ~50% (moderate) and ~80% (high) of peak oxygen uptake. In the EX+CO₂, the participants inspired hypercapnic gas (2% CO₂) during high-intensity exercise. In the CON, they performed the cognitive tasks without exercise. 

Results: Middle cerebral artery mean velocity (MCAv) increased during high-intensity exercise in the EX+CO₂ relative to the EX [69.4 (10.6) cm.s-1, vs. 57.2 (7.7) cm.s-1, P < 0.001]. Accuracy of the cognitive tasks was impaired during high-intensity exercise in the EX [84.1 (13.3) %, P < 0.05] and the EX+CO₂ [85.7 (11.6) %, P < 0.05] relative to rest [EX: 95.1 (5.3) %, EX+CO₂: 95.1 (5.3) %]. However, no differences between the EX and the EX+CO₂ were observed (P > 0.10). These results demonstrate that restored CBF did not prevent cognitive impairment during high-intensity exercise. 

Conclusion: We conclude that a reduction in CBF is not responsible for impaired cognitive performance during high-intensity exercise.