The relationship between exercise intensity, cerebral oxygenation and cognitive performance in young adults.

Purpose: To assess the relationship between exercise intensity, cerebral HbO2 and cognitive performance (Executive and non-Executive) in young adults.

Methods: We measured reaction time (RT) and accuracy, during a computerized Stroop task, in 19 young adults (7 males and 12 females). Their mean ± SD age, height, body mass and body mass index (BMI) were 24 ± 4 years, 1.67 ± 0.07 m, 72 ± 14 kg and 25 ± 3 kg m(-2), respectively. Each subject performed the Stroop task at rest and during cycling at exercise of low intensity [40% of peak power output (PPO)], moderate intensity (60% of PPO) and high intensity (85% of PPO). Cerebral oxygenation was monitored during the resting and exercise conditions over the prefrontal cortex (PFC) using near-infrared spectroscopy (NIRS).

Results: High-intensity exercise slowed RT in both the Naming (p = 0.04) and the Executive condition (p = 0.04). The analysis also revealed that high-intensity exercise was associated with a decreased accuracy when compared to low-intensity exercise (p = 0.021). Neuroimaging results confirm a decrease of cerebral oxygenation during high-intensity exercise in comparison to low- (p = 0.004) and moderate-intensity exercise (p = 0.003). Correlations revealed that a lower cerebral HbO2 in the prefrontal cortex was associated with slower RT in the Executive condition only (p = 0.04, g = -0.72).

Conclusion: Results of the present study suggest that low to moderate exercise intensity does not alter Executive functioning, but that exercise impairs cognitive functions (Executive and non-Executive) when the physical workload becomes heavy. The cerebral HbO2 correlation suggests that a lower availability of HbO2 was associated with slower RT in the Executive condition only.