Physical activity, aerobic fitness and brain white matter: their role for executive functions in adolescence

Physical activity and exercise beneficially link to brain properties and cognitive functions in older adults, but it is unclear how these results generalise to other age groups. During adolescence, the brain undergoes significant changes, which are especially pronounced in white matter. Existing studies provide contradictory evidence regarding the influence of physical activity or aerobic-exercise on executive functions in youth. Little is also known about the link between both aerobic fitness and physical activity with white matter during puberty. For this reason, we investigated the connection between both aerobic fitness (20-m shuttle run) and physical activity (moderate-to-vigorous intensity physical activity) with white matter in 59 adolescents (12.7-16.2 years). We further determined whether white matter interacts with the connection of fitness or physical activity with three core executive functions (sustained attention, spatial working memory and response inhibition). Our results showed that only the level of aerobic fitness, but not of physical activity was related to white matter properties. Furthermore, the white matter of specific tracts also moderated the links of aerobic fitness and physical activity with working memory. Our results suggest that aerobic fitness and physical activity have an unequal contribution to the properties of white matter in adolescent brains. We propose that the differences in white matter properties could underlie the variations in the relationship between either physical activity or aerobic fitness with working memory.