Physical fitness, academic achievement and brain in children

Resumen

The major aims of the present International Doctoral Thesis were: provide new methods for physical fitness assessment in preschool children, and provide reference standards for interpreting fitness assessment (Section 1); and to examine the associations between physical fitness and academic achievement in preadolescent children, as well as to explore the role of metabolic healthy overweight/obesity phenotype in the brain and its associations with academic achievement (Section 2). To address these aims, nine studies were conducted in the context of two projects. The PREFIT project (Section 1, Studies I to VII) is a cross-sectional study that takes place in 2 stages: first, a methodological stage conducted in Granada and a second, a multi-center stage carried out in more than 3000 Spanish pre-schoolers from 10 Spanish cities, for a better understanding of physical fitness assessment in this age group. The ActiveBrains project (Section 2, Studies VIII to IX) is a randomized controlled trial that aimed to examine the effect of physical exercise programme on physical and mental health in overweight/obese children. The present Thesis focused on cross-sectional analyses using the baseline data. The main findings and conclusions derived from the nine studies included in this thesis were: I) The PREFIT battery hereby proposed is based on the output of the current systematic review in preschool children; II) The intra-instrument test–retest reliability was excellent for all of the dynamometers used for handgrip strength assessment in the PREFIT battery; III) The PREFIT 20m shuttle run test is feasible, maximum and reliable in preschool children; IV) The PREFIT battery is a feasible and reliable tool to assess physical fitness in preschool children yet standing long jump has shown mixed findings. The one-leg stance test showed poor reliability in our study, not supporting thus its use in 3 to 5 years-old; V and VI) We provide reference standards for physical fitness and anthropometry by sex and age from a relatively large sample of preschool children geographically distributed across Spain; and VII) Higher prevalence of overweight/obesity in Spain compared with Sweden is present already at early childhood, while differences in physical fitness components showed mixed findings. In regards to the Section 2, the main findings were: VIII) Not only cardiorespiratory fitness but also muscular strength and speed-agility were positively associated with academic achievement in overweight/obese children. Physical activity did not demonstrate an association with any of the academic outcomes studied; and IX) Metabolically healthy overweight/obesity related to higher gray matter volume and total brain volume compared to metabolically unhealthy overweight/obese children, which in turn related to better academic achievement, although such associations disappeared or were attenuated after adjusting for cardiorespiratory fitness. The results of this International Doctoral Thesis enhance our understanding about how to assess and interpret physical fitness and fatness in preschool children; and also how physical fitness relate with academic achievement and the metabolically healthy overweight/obesity phenotype with brain in preadolescent children. These results will lead to future prospective and intervention investigations on the physical and brain health at childhood and later in life.