The Role of the Time of Day in the Effects of Exercise on Memory in Heathy Young Adults

Cumulative evidence indicates that a single bout of exercise has beneficial impacts on memory in young adults. From a physiological perspective, acute exercise leads to changes of heart rate variability (HRV), which is associated with memory retrieval process. From a psychological perspective, acute exercise increases the arousal level and thus facilitates cognitive processing including memory storage and retrieval. Such HRV- and/or arousal-based effects of exercise on memory could be differed by the time of day in young adults based on their circadian rhythms of HRV. Moreover, young adults prefer afternoon or evening to morning in their circadian rhythms, demonstrating less wakefulness and lower memory performance in the morning relative to afternoon. Based on the potential psychophysiological mechanisms, exercise could impact young adults' memory differently by the time of day. The inv