# The acute effect of sprint interval training on the immune system: a systematic review and meta-regression analysis

## TL;DR

A single session of sprint interval training boosts immune cell counts and cytokine levels, with differences based on whether individuals are trained or untrained.

## Contribution

This study provides a systematic review and meta-analysis of the acute immune effects of sprint interval training in healthy individuals.

## Key findings

- Sprint interval training significantly increases total leukocyte and neutrophil counts with minimal variability.
- Trained athletes show a stronger interleukin-6 response and stable salivary IgA compared to untrained individuals.
- Lymphocyte count increases with a U-shaped dose–response to repetition duration.

## Abstract

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.

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.

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 (I2 = 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), I2 = 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)].

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.

https://www.crd.york.ac.uk/PROSPERO/view/CRD420251140621.

This graphical abstract summarizes the main findings regarding the acute effects of a single session of sprint interval training (SIT) on immune cells, cytokines, and mucosal immunity. Created in BioRender. Liang, W. (2026) https://BioRender.com/9ruwz3p.Infographic showing the acute immunological response to a single bout of sprint interval training. It illustrates the process from the trigger (supramaximal sprint bouts) causing a high metabolic demand and catecholamine surge, leading to increased hemodynamic shear stress. This results in core immune cell mobilization from bone marrow and spleen, increasing total leukocytes, neutrophils, and lymphocytes. It continues with cytokine response: trained athletes show a larger IL-6 release compared to untrained individuals. Training status affects mucosal immunity; trained athletes maintain stable sIgA, while untrained individuals may experience a decrease. Legend indicates effects and variables.

This graphical abstract summarizes the main findings regarding the acute effects of a single session of sprint interval training (SIT) on immune cells, cytokines, and mucosal immunity. Created in BioRender. Liang, W. (2026) https://BioRender.com/9ruwz3p.