This study evaluates the effect of a 16-week moderate-to-vigorous physical activity (MVPA) program on physical fitness and gut microbiota in healthy school-aged children. Participants will be randomly assigned to either an MVPA intervention group or an attention-control group. The primary outcome is the change in a composite physical fitness score. Secondary outcomes include changes in gut microbiota diversity and composition.
This is a two-arm, parallel-group, randomized controlled trial with 1:1 allocation, conducted as an intervention extension of a previously published cross-sectional cohort study (Pan et al., Sci Rep 2025;15:21351; GSA-Human HRA010530). Healthy children aged 7-11 years at the time of intervention baseline (December 2025), who were 6-9 years old when they participated in the 2023 cross-sectional study in Weifang, Shandong, will be included. In the 2023 baseline study, 120 children were sampled across four PA×PF quadrant groups defined by quartiles of physical activity (PA) and physical fitness (PF): P1 (low PA-low PF), P2 (high PA-low PF), P3 (low PA-high PF), and P4 (high PA-high PF). Of these, 113 provided valid baseline fecal samples and physical fitness data. These 113 participants were re-contacted and re-randomized 1:1 to MVPA or attention-control arms in December 2025. Randomization is stratified by baseline PA×PF quadrant (P1-P4) to ensure balanced allocation of baseline gut microbiome phenotypes across intervention and control arms. The reported enrollment of 113 refers to the number re-randomized at the intervention baseline (T1), not new recruits. The intervention group will receive a 16-week structured MVPA program (3 sessions/week, 45-60 min/session). The control group will receive attention-matched sedentary activities (e.g., reading, crafts) and will be offered the MVPA program after the trial (waitlist). This is a PROBE-design trial: participants and intervention instructors are not blinded to group assignment, while outcome assessors (physical fitness tests) and laboratory/bioinformatics personnel (microbiota analysis) are blinded to allocation. The database uses codes (e.g., Group A/B) until primary analysis is complete. The primary analysis will follow the intention-to-treat (ITT) principle. The study aims to (1) determine whether the MVPA intervention improves physical fitness and modulates the gut microbiota, and (2) determine whether baseline PA×PF quadrant membership and baseline abundance of key microbial taxa (Akkermansia, Faecalibacterium, Subdoligranulum, Bacteroides coprocola) modify the intervention response, thereby informing precision exercise prescription strategies. Ethics and Oversight: This study operates under a collaborative framework in which the China Institute of Sport Science (CISS) serves as the primary institution responsible for ethical oversight and scientific integrity, while Aiyoudong Children and Youth Sports Health Research Institute serves as the implementing institution. Ethical approval was granted by the Ethics Committee of CISS (approval number: CISSLA20230110), covering both the 2023 baseline cross-sectional study and the current intervention extension. Aiyoudong Institute, which does not maintain an independent ethics committee, conducts the intervention under CISS oversight through a formal inter-institutional data use and oversight agreement. Written informed consent was obtained from legal guardians and assent from child participants at both baseline (2023) and intervention enrollment (December 2025). Exploratory aim: to characterise the co-variation between intervention-induced changes in physical activity, physical fitness, gut microbiota, and psychosocial and behavioural measures, with the gut microbiota as the central node. These analyses are exploratory and hypothesis-generating, and no specific direction of change in the psychosocial or behavioural measures is presumed.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
SINGLE
Enrollment
113
A 16-week structured moderate-to-vigorous physical activity program.
Time-matched sedentary activities such as reading, science experiments, or crafts.
Aiyoudong Children and Youth Sports Health Research Institute
Weifang, Shandong, China
Change in Composite Physical Fitness Z-score
Change from Baseline to 16 weeks in a composite physical fitness z-score. The score is calculated based on the age-appropriate items and weighting from the "National Student Physical Health Standard (2014 Revision)". The scale is a standardized z-score with a mean of 0 and a standard deviation of 1, based on a reference population. There are no theoretical upper or lower limits, but values typically range from -3 to +3. A higher score indicates better overall physical fitness.
Time frame: Baseline and 16 weeks
Change in Gut Microbiota Alpha Diversity
Change from Baseline to 16 weeks in alpha diversity indices (Shannon and Chao1) of the gut microbiota, assessed via 16S rRNA gene sequencing. The Shannon index has a minimum value of 0, with no theoretical maximum. The Chao1 index estimates species richness with a minimum equal to the number of observed species, and also has no theoretical maximum. For both indices, higher values indicate greater diversity and are generally considered to reflect a healthier gut microbiome.
Time frame: Baseline and 16 weeks
Difference in Gut Microbiota Beta Diversity
Difference in gut microbiota community structure (beta diversity) between the MVPA and control groups. This will be assessed using a Permutational Multivariate Analysis of Variance (PERMANOVA) on Bray-Curtis and UniFrac distance matrices. The outcome will be reported as an R-squared value, representing the percentage of variance in community structure explained by group assignment, and a p-value. A larger R-squared value and a smaller p-value would indicate a more significant difference between the groups.
Time frame: Baseline and 16 weeks
Change in Body Mass Index (BMI) Z-score
Change from Baseline to 16 weeks in age- and sex-specific BMI z-score. This is a standardized score with a mean of 0, based on a reference population, and has no theoretical upper or lower limits. A higher score indicates a higher BMI relative to peers. In the context of this study focusing on healthy weight, an increase in the z-score is generally considered a worse outcome.
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Time frame: Baseline and 16 weeks
Heterogeneity of Treatment Effect Across Baseline PA×PF Quadrants
Heterogeneity of treatment effect (HTE) of the MVPA intervention on primary and secondary outcomes across the four pre-specified baseline phenotype groups (P1: low PA-low PF; P2: high PA-low PF; P3: low PA-high PF; P4: high PA-high PF) defined in the 2023 cross-sectional study. HTE will be assessed by including a Treatment × Baseline Quadrant interaction term in mixed-effects models. A statistically significant interaction (p \< 0.05) would indicate that the intervention effect differs across baseline microbiome phenotypes. Effect sizes will be reported separately for each quadrant with 95% confidence intervals.
Time frame: Baseline and 16 weeks
Baseline Microbial Taxa as Effect Modifiers of Intervention Response
Pre-specified analysis of whether baseline relative abundance (continuous, log-transformed) of Akkermansia, Faecalibacterium, Subdoligranulum, and Bacteroides coprocola modifies the MVPA intervention effect on composite physical fitness z-score and alpha diversity. Interaction terms (Treatment × Baseline Taxon Abundance) will be tested in mixed-effects models.
Time frame: Baseline and 16 weeks