Carbohydrate mouth rinse during physical activity to improve cognitive function: a randomized cross-over trial

The dorsolateral prefrontal cortex (DLPFC) is a brain region responsible for executive function. Recent studies have reported that low-intensity physical activity (LPA) can activate this region and improve executive function. Carbohydrate mouth rinse (CMR), an ergogenic conditioning method in sports science, has been shown to activate the DLPFC. This study hypothesized that LPA-induced improved executive function could be synergistically enhanced by CMR. We investigated the impact of combining LPA with CMR to improve executive function. Seventeen healthy university students (eight male, nine female) participated. For LPA, instead of commonly-used exercise modalities, such as bicycle ergometers or treadmills, a seated dual-task exercise (DE) was employed that involved performing cognitive tasks and physical activity simultaneously, which is considered effective for cognitive function. Four trials were conducted using a crossover design: trial 1 control (CON), trial 2 (CON+CMR), trial 3 (DE), and trial 4 (DE+CMR). The Trail Making Test Type B (TMT-B, Japanese version) and Stroop Test (ST, Japanese version) assessed cognitive function, and CMR was administered with a 6% glucose solution four times during CON and DE. The results indicated a significant interaction in Interference Rate I of the ST, showing improved performance due to DE. An interaction was also observed in Interference Rate II, highlighting enhanced performance when DE was combined with CMR. Although no interaction was found in TMT-B, a pre-post comparison revealed improved performance in the DE+CMR trial. These findings suggest the potential for further improvement in executive function when DE is combined with CMR.