Differential Inflammatory Response to Exhaustive Exercise in Trained and Untrained Individuals: Potential Biomarkers of Training Adaptation

Background: Acute exercise induces measurable inflammatory and hematological responses, which may differ according to training status. Methods: Trained soccer players and sedentary controls completed a progressive exercise test until exhaustion. Blood samples were collected at six time points (up to 48 h post-exercise). Gene expression was assessed using real-time PCR, protein concentration via ELISA, and leukocyte, lymphocyte and neutrophil counts through routine hematology. Analyses included between-group comparisons, within-group time effects, and gene–protein correlations. Results: Sedentary individuals showed delayed increases in TNF-α mRNA (p < 0.05), whereas athletes maintained stable levels. Athletes exhibited consistently higher TNFR-1 expression (p < 0.05), while TNFR-2 showed no differences between groups. IL-4 expression was higher in athletes 30 min (p = 0.038) and 24 h after test (p = 0.002), whereas IL-4 protein decreased in sedentary subjects after 6 h (p = 0.009) and 24 h (p = 0.019). IL-4Rα was transiently elevated post-exercise in sedentary individuals and briefly suppressed in athletes (p = 0.041). Hematological responses showed stronger leukocytosis and neutrophilia in sedentary individuals. Conclusions: The temporal inflammatory patterns differed substantially between groups, indicating more efficient resolution dynamics in trained individuals. These findings highlight practical value for monitoring adaptation and recovery.