The effect of repeated sprints on immunological modulation and the role of fat-free mass, biological maturation and dietary inflammatory index in male athletes: a quasi-experimental study with insights for training loads control.

Background: Repeated sprint exercise (RSE) induces inflammation, which may be modulated by fat-free mass (FFM), biological maturation (BM), and dietary patterns, assessed by the Dietary Inflammatory Index (DII). Aim: To examine the influences of FFM, BM, and DII on cytokine responses to RSE in male athletes. Methods: A study with a quasi-experimental approach and cross-sectional design with a sample of 30 male athletes (20-adolescents, 10-adults). Blood samples were collected pre-, immediately after, 2 h and 24 h after RSE (3-sets of 6 × 35-m sprints). IL-1β, IL-6, IL-8, and IL-10 were analyzed via flow cytometry. FFM was assessed by DXA, BM by predictive models, and DII by 24 h dietary recalls. Prior exploratory analyses included Spearman's and partial correlations, and Mann-Whitney- Results: The GLMMs confirmed that BM, FFM, and DII significantly influenced cytokine responses ( Conclusion: FFM, BM, and DII play key roles in shaping the inflammatory response to RSE and should be considered when prescribing training loads to optimize recovery and performance.