AUTHOR=de Almeida-Neto Paulo F. , Fernandes E. Alana D. , de Assis Gilmara G. , Suzuki Katsuhiko , da Costa Roberto F. , Atanásio Lívia de Melo , Pinto Vanessa Carla Monteiro , Aidar Felipe J. , Cabral Breno Guilherme de Araújo Tinôco , Dantas Paulo Moreira Silva 

TITLE=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

JOURNAL=Frontiers in Sports and Active Living

VOLUME=Volume 7 - 2025

YEAR=2025

URL=https://www.frontiersin.org/journals/sports-and-active-living/articles/10.3389/fspor.2025.1662761

DOI=10.3389/fspor.2025.1662761

ISSN=2624-9367

ABSTRACT=BackgroundRepeated 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).AimTo examine the influences of FFM, BM, and DII on cytokine responses to RSE in male athletes.MethodsA 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-U-tests. Main analyses were conducted using Generalized-Linear-Mixed-Models (GLMM).ResultsThe GLMMs confirmed that BM, FFM, and DII significantly influenced cytokine responses (p < 0.05). FFM emerged as a significant predictor of IL-1β (p = 0.0023). For IL-6, there was a time effect (p < 0.001) and a Time × BM interaction (p = 0.040), with FFM and DII being significant predictors in both groups. A similar interaction was observed for IL-8 (p = 0.036). For IL-10, there was a Time × BM interaction (p < 0.001), where adults showed superiority over adolescents (p < 0.05). Post hoc analyses revealed that adolescents with lower FFM had a more prolonged inflammatory response (increased-IL-6), while adults with higher FFM demonstrated a more effective anti-inflammatory capacity (increased-IL-10).ConclusionFFM, 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.