Relationship between physical activity, fitness and brain morphology in youth

Abstract

Growing evidence has displayed a relationship between physical activity, fitness and cognitive functions, yet the underlying mechanisms and changes in brain morphology explaining this connection are still quite unknown. The current study examined whether physical activity or physical fitness is related with regional brain volume of cortical thickness in youth.

The subjects were 35 Finnish adolescents (14.1 ±0.7 years, 23 females & 12 males), a subsample from Active, Fit and Smart (AFIS) – research project. Measurements included objective physical activity measurement with accelerometers, physical fitness test battery and brain imaging procedure with magnetic resonance imaging (MRI). From the larger study sample of the AFIS – research project, two groups were formed based on the physical activity measurements, active (n=18) and non-active (n=17). The active group included the most physically active subjects, measured as the average daily time involved in moderate-to-vigorous activity, and the non-active group included the most inactive subjects. The relationship between physical activity and brain morphology was examined by comparing the two groups using the analysis of covariance, controlling the effect of age, puberty status and body mass index. The relationship between physical fitness and brain morphology was examined by looking at correlations between the physical fitness tests and chosen brain variables.

It was found that physical activity had a positive relationship with the thickness of the right parahippocampal cortex [F(1, 30)=4.44, p<0.05)]. Physically more active subjects expressed a thicker right parahippocampal cortex compared to less active subjects. A relationship was also found between physical activity and the thickness of the left paracentral cortex, yet this finding lost significance after controlling the effect of age [F(1, 30)=2.50, p=0.12)]. No other brain region displayed a connection with the level of physical activity and no significant correlations were detected between physical fitness and the brain variables. These findings imply that especially the area of right parahippocampal cortex might be susceptible to physical activity induced changes in youth, and that physical activity does not necessarily have to improve physical fitness to cause changes in brain morphology.