The Acute Effect of Exercise Intensity on Cognitive Function

Abstract

Recent research has found that regular exercise has a positive effect on cognitive function. Some studies indicate that even an acute session of exercise has a slight positive effect on cognitive function, though factors moderating this effect have not been thoroughly examined. Exercise intensity and timing of cognitive assessment may have an interactive effect on cognitive changes after exercise. Previous research suggests that moderate intensity exercise has the most consistent benefit to cognitive function. In contrast, studies find positive, negative, or null effects to cognitive function after high intensity exercise, where the timing of the post-exercise assessments may account for the observed differences. Since high-intensity interval training (HIIT) is an increasingly popular form of exercise due to equal or greater cardiovascular adaptation for reduced exercise time, understanding its cognitive effects is of interest. The primary objective of the study was to compare the cognitive effects of an acute bout of HIIT to both moderate intensity continuous training (MCT) and rest. The secondary objective was to compare the timeline of the cognitive effects between these three sessions. Twenty-two participants performed 28.5min of HIIT, MCT, and rest on three separate days, each 2 weeks apart. The rest session was performed first and the subsequent exercise sessions were randomized. Cognitive function was assessed using a modified Flanker task with concurrent electroencephalography (EEG) before and 0, 15, 30, and 45min post-intervention. The hypothesis that cognitive function would improve after MCT and HIIT was not supported. Though there was some variability in cognitive function post-exercise, cognitive function was not significantly different before to after exercise or in comparison to the rest session. However, measures of cognitive function were often better prior to the exercise sessions than before exercise, possibly due to an anticipatory effect prior to exercise or learning carry-over after the rest session, which complicated interpretation of results. Of note, only a small number of prior studies included a baseline assessment of cognitive function in each session. Future research should examine the influence of the anticipation of exercise on cognitive function to better understand whether it is the psychological or physical stress imposed by exercise that enhances cognitive function.