Objective: To systematically evaluate the safety and efficacy of high-intensity interval training in children and adolescents. Design: Systematic Review and Meta-Analysis. Methods: Eight databases were searched. Descriptive analysis of the efficacy and safety of high-intensity interval training on body shape, cardiorespiratory fitness, and metabolic risk markers for cardiovascular disease between children and adolescents. Subgroup analysis was performed with age, participants, intervention

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... and exercise frequency as covariates. Results: 47 studies included 2995 children and adolescents. Meta-analysis results showed that high-intensity interval training significantly improved cardiorespiratory fitness indicators (VO2max, SBP, DBP and HRmax) and cardiovascular disease metabolic risk indicators (TC, HDL-C). HIIT had no significant effect on body shape indicators (BMI, BF% and WC) and some cardiometabolic indicators (TG and LDL-C). Conclusion: Current evidence shows insufficient evidence that high-intensity interval training with intermittent running as the main form of exercise improves body shape indicators in children and adolescents. Nevertheless, it deserves to recommend for the purpose of improving cardiorespiratory fitness and reducing the metabolic risk of cardiovascular disease.