Abstract
This study investigated the diversity, structure, dominant microbial populations, and their relationships with physical fitness (PF) and physical activity (PA) metrics within the gut microbiota of children by comparing the gut microbiome composition and functional differences across four groups: low PA-high PF, high PA-high PF, high PA-low PF, and low PA-low PF. A total of 6,074 children aged 6-9 years were selected from full-time ordinary primary and secondary schools. Based on the quartiles of PF and PA, we sampled 120 individuals from each of the four groups (30/group) and collected fecal samples for high-throughput sequencing to analyze the gut microbiome composition. This study revealed that children with high PF exhibited a more abundant and diverse gut microbiome within the same PA level group. Under high PA conditions, the Chao1 and Shannon indices of the high PF group were significantly higher. Different dominant microbial taxa were identified within each group, and specific microbial populations were significantly correlated with various physical and exercise-related indices. This study indicates that the composition of children's gut microbiota varies significantly based on the combined levels of PA and PF. Children with high PF show greater microbial diversity within similar PA levels, particularly under high PA conditions.