Background Sprint interval training (SIT) is an increasingly popular time-efficient training paradigm; however, its acute impact on the immune system remains ambiguous due to inconsistent findings across studies. This systematic review and meta-analysis aimed to quantitatively evaluate the acute effects of a single SIT session on key immunological markers in healthy individuals. Methods We systematically searched PubMed, Web of Science, SPORTDiscus, the Cochrane Library, Embase, and Scopus for experimental studies assessing acute immunological changes following a single bout of SIT in healthy participants. Pooled standardized mean differences (SMDs) and 95% confidence intervals (CIs) were calculated using a random-effects model. Non-linear meta-regression and subgroup analyses were performed to investigate sources of heterogeneity, and the certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. Results A total of 21 studies, comprising 359 participants, were included in the analysis. The meta-analysis analysis revealed that a single session of SIT induced a robust and significant increase in total leukocyte count SMD = 2.68, 95% CI (1.79, 3.57) and neutrophil count SMD = 1.04, 95% CI (0.75, 1.34), with the latter exhibiting zero heterogeneity ( I 2 = 0%). Lymphocyte count SMD = 3.83, 95% CI (1.07, 6.59) also increased significantly, showing a U-shaped dose–response relationship with repetition duration. Interleukin-6 (IL-6) increased significantly SMD = 1.10, 95% CI (0.49, 1.71), with subgroup analysis revealing a twofold greater response in trained athletes compared to untrained individuals. In contrast, salivary IgA (sIgA) remained stable in trained athletes SMD = 0.07, 95% CI (−0.31, 0.45), I 2 = 0% but showed high variability in untrained groups. Plasma interleukin-10 (IL-10) concentration exhibited a small, non-significant increasing trend SMD = 0.18, 95% CI (−0.06, 0.43). Conclusion A single session of SIT elicits a potent acute systemic immune response, characterized by a highly conserved mobilization of circulating leukocytes, particularly neutrophils. This response is significantly modulated by individual training status: athletes exhibit a distinct immunometabolic profile characterized by a robust IL-6 release and stable mucosal immunity (sIgA), whereas untrained individuals show more variable responses. These findings provide critical evidence for understanding the physiological stress of SIT and can inform training and recovery practices to safeguard immune health. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420251140621 .
Liang et al. (2026) studied this question.