Thompson, K. G., Turner, L., Pritchard, J., Dodd, F., Kennedy, D. O., Haskell, C., Blackwell, J. R., & Jones, A. M. (2013). Effect of dietary nitrate on cerebral oxygenation and cognitive performance during cycle exercise. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 2424.

This study investigated the influence of dietary nitrate supplementation on cerebral oxygenation, effort perception, mental fatigue, and cognitive performance during exercise. Ss (N = 16) ingested 500 ml of nitrate-rich beetroot juice (containing 5 mmol nitrate) or a placebo on separate occasions in a double-blind cross-over designed experiment. After a 90-minute absorption period, Ss cycled for 20 minutes at 50% and then 70% VO2peak before cycling at 90% VO2peak to volitional exhaustion. Ss completed cognitive tasks (RVIP for nine minutes, Stroop test for nine minutes) prior to exercise, during the 50% and 70% VO2peak stages, and following the 90% VO2peak stage.

Following dietary nitrate supplementation, plasma [nitrite] was found to have increased and systolic blood pressure decreased compared to placebo. Change in cerebral deoxyhemoglobin concentration was significantly lower with nitrate supplementation compared to placebo during the pre-exercise cognitive tasks, as well as during exercise at 50% and 70% VO2peak and post-exercise. Cerebral oxyhemoglobin concentration and total hemoglobin concentration responses were similar between treatment conditions. Changes in cognitive task performance, mental fatigue (100 mm line scale), ratings of perceived exertion, and mood (fatigue and vigor on the BRUMS questionnaire) were similar in both treatment conditions. Exercise tolerance at 90% VO2peak significantly increased In the dietary nitrate condition.

Implication. Nitrate supplementation prior to exercise did not improve cognitive performance or attenuate mental fatigue or subjective effort responses during moderate to severe exercise.

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