Acute and protocol-dependent effects of aerobic exercise on neurobiochemical indices and neuropsychological performance of working memory

This study aimed to clarify the effects of high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MICE) protocols on peripheral neurotransmitters and on the neuropsychological performance of working memory and to explore underlying correlations. In a randomised cross-over trial, twenty-two adults in late middle age or older completed a single session of HIIE, MICE, or a control condition (rest) in counterbalanced order with a 7-day washout. Neuropsychological indices of working memory and neurotransmitter (norepinephrine, dopamine, and serotonin) levels were measured at baseline and after an intense bout of either HIIE or MICE, or an intervention without exercise. Analyses of the results revealed no significant effect of HIIE on the neurotransmitters, but significantly high levels of norepinephrine and serotonin were induced by MICE. In terms of neuropsychological performance, a single session of HIIE and MICE shortened the participants' reaction times (RTs), whereas only MICE caused a significant increase in accuracy rates (ARs). Significant correlations were found between the changes in norepinephrine levels and ARs/RTs before and after the HIIE and MICE interventions, respectively. The results of this study suggest that an intense MICE protocol triggers higher norepinephrine and serotonin levels than HIIE does. The possible neurobiochemical factor (i.e., norepinephrine) underlying the HIIE/MICE-induced neuropsychological benefits (i.e., improved ARs and RTs) for working memory encoding and maintenance appears to be protocol-dependent. Systematic and prolonged investigations are required to further understand the effects/mechanisms specific to each exercise protocol in order to optimize the benefits of aerobic exercise interventions for long-term neurobiochemical and neuropsychological health.