The characteristics of cerebral cortical oxygenation levels and functional connectivity under upper and lower limb exercise-induced fatigue

This study aims to explore the impact of fatigue induced by different limb exercises on cerebral cortical oxygenation levels and functional connectivity strength using functional near-infrared spectroscopy (fNIRS). Fatigue was induced using an upper limb ergometer or a lower limb ergometer, with the load increasing gradually each minute. fNIRS covering the prefrontal cortex and motor cortex were used to collect data during the resting state, both before and after fatigue induction. A two-way ANOVA was conducted to examine differences in oxyhemoglobin (HbO₂) and functional connectivity before and after fatigue induction in both groups, with the significance level set at 0.05. Exercise-induced fatigue in both the upper and lower limbs leads to a significant decrease in cerebral cortical oxygenation levels. Upper limb fatigue leads to a significant reduction in functional connectivity, there were significant decreases in connectivity within the motor cortex, between the motor cortex and frontal regions, and between the right ventrolateral prefrontal cortex and other frontal regions. Conversely, no significant changes were observed before and after lower limb fatigue. Future studies should focus on examining the extent to which how changes in the cerebral cortex, induced by exercise fatigue, are linked to exercise- and/or performance-related outcomes.