Effects of a 16-week Moderate-to-Vigorous Physical Activity Program on Physical Fitness and Gut Microbiota in Children: A Randomized Controlled Trial

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).