Soichi ANDO (安藤 創一)

Research on physical activity (PA) and health has a fundamental concern with dose-response relationships. The variables of (1) Frequency, (2) Intensity, (3) Time, and (4) Type (i.e., the FITT principle) have traditionally been used to operationalize the dosage of PA. We consider some limitations of FITT and propose that it can be complemented by the additional variable density (from the German exercise and training variable Belastungsdichte), which can be defined as the timing of successive work bouts within a single PA bout as well as the timing between successive PA bouts within a specific time period; it does so by quantifying the temporal intervals between successive work or PA bouts (i.e., time spent at a lower PA intensity or resting such as in napping/sleeping or sedentary behaviors). Using the field of PA and brain health as an example, we discuss the opportunities and challenges for further research employing the variable density and consider its potential to improve the understanding of dose-response relationships between PA and health outcomes.

It has been suggested that acute physical exercise at low to moderate intensity improves cognitive function, as shown by improvements in cognitive performance. Decades of research have explored or discussed physiological mechanisms underlying cognitive improvements induced by acute exercise. However, the precise physiological mechanisms responsible for improvements in cognitive function remain to be elucidated. There is a large body of evidence to suggest that cognitive function is linked with dopamine (DA) in the brain. Rodent studies have shown that acute exercise releases neurotransmitters in the brain. Recent studies using positron emission tomography (PET) have also suggested that acute exercise released endogenous DA in humans. Furthermore, it appears that endogenous DA release is linked with improvements in cognitive function induced by acute exercise. Therefore, in this chapter, we focus on DA and discuss it as a promising candidate to account for exercise-cognition interaction, particularly improvement in cognitive function induced by acute exercise. We propose that further studies using PET would be helpful to progress our understanding of improvements in cognitive function induced by acute exercise.