The effects of exercise training on inflammatory markers in children and adolescents: A systematic review and meta-analysis

Introduction and aim: Exercise training is effective for improving cardiometabolic health in children and adolescents, but less is known about its impact on inflammatory markers. We therefore, undertook a systematic review and meta-analysis to investigate the role of exercise training on pro-inflammatory cytokines including interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and C-reactive protein (CRP) in children and adolescents. Method: A comprehensive search was conducted in three electronic databases including PubMed, Web of Science, and Scopus, from inception to December 2023 to identify exercise trials with and without control groups, involving participants with mean ages ranging from >= 6 to < 18 years, of age with measurements of at least one of the following pro-inflammatory cytokines IL-6, TNF-alpha, or CRP. Standardized mean differences (SMD) and 95 % confidence interval (ICs) were calculated using random effects models. Results: Thirty-eight studies involving 2043 children and adolescents were included. The results show that exercise training resulted in significant reductions in IL-6 [SMD: -0.44; 95 % CI: -0.68, -0.21; P = 0.001] and CRP [SMD: -0.28; 95 % CI: -0.41, -0.16; P = 0.001], but not TNF-alpha [SMD: -0.15; 95 % CI: -0.38, -0.07; P = 0.19]. Subgroup analyses showed that IL-6 and CRP were reduced with aerobic training in adolescents, as was CRP with high-intensity interval training. Conclusion: These results provide evidence that exercise training is effective for reducing IL-6 and CRP in adolescents, but not in children, and any benefits may be modulated by the type of exercise performed.