Effect of repeated sprint exercise on immunological responses in adult and adolescent athletes at different stages of biological maturation: a-quasi-experimental-trial

Abstract

Repeated sprint exercise (RSE), widely used in intermittent sports, induces immune changes critical to address for optimizing training and reducing health risks in youth athletes, especially across biological maturation (BM) stages. We analyzed RSE effects on immune factors in adolescent and adult athletes, considering BM stages. Twenty-nine male intermittent-sport athletes (19 hebiatric: 10 pre-peak height velocity [PHV] [12.1 ± 0.6 years], 9 circum-PHV [13.8 ± 0.7 years]; 10 adults [23.2 ± 2.1 years]) performed RSE (3 × 6 × 35 m sprints, 10-sec rest, 5 min interset). Blood was collected pre-, post-, 2 h, and 24 h post-RSE to assess lactate, leukocyte subsets (neutrophils, monocytes, lymphocytes, T/B cells, NK-cells), and cytokines. According to international guidelines for athletic classification, 72% of the participants in this study were classified as level 2 (regional; ~12-19% of the global population), 17% as level 3 (national; ~0.014% of the global population), and 11% as level 4 (international; ~0.0025% of the global population). RSE elevated leukocytes in all groups, with adults showing higher neutrophils and hebiatric athletes elevated T/B cells (p < 0.05). Pre-PHV exhibited reduced neutrophil/cytokine responses versus circum-PHV/adults (p < 0.05). Circum-PHV displayed post-RSE CD4+/CD8 + rises, while adults had the lowest CD4⁺ (p < 0.05). Pre-PHV peaked in NK/B-cells at 2 h/24 h; adults showed elevated IL-6/IL-8 (p < 0.05). All parameters normalized by 24 h. Immune responses to RSE differ by BM stage, with adults exhibiting heightened inflammation. Tailoring training to BM stages may optimize performance and reduce immunosuppression risks, particularly in hebiatric athletes.

Keywords: Cytokine; Hematology; Leukocyte; Lymphocyte; Sport.

Fig. 1

Procedures. RAST running-based anaerobic sprint test, PHV peak height velocity, n absolute number, RSE repeated sprint exercise, DXA dual-energy X-ray absorptiometry, WURSS-21 Wisconsin upper respiratory symptom survey-21, IPAQ international physical activity questionnaire. This figure was created in https://BioRender.com.

Fig. 2

Graphical representation of dot-plot histograms obtained by flow cytometry of T helper, T cytotoxic, B cells and natural killer cell lymphocyte subpopulations. (a) Cellular heterogeneity based on cellular complexity (SSC-A) and lymphocyte parameters. (b) Histograms for individual assessment of cellular event acquisition. (c) Highlight of the final gated immune cell populations based on specific surface markers.

Fig. 3

Behavior and comparison of serum lactate levels. (mmol/L): millimoles per liters. ‡: Higher than the other time points. †: Higher than the Before time point. A: Higher than the other groups. Statistical analysis: Repeated measures ANOVA with Bonferroni post-hoc tests. d: Effect size by d-Cohen.

Fig. 4

Comparisons between total leukocyte levels (a) and mononuclear subpopulations (b) and granulocytes (c). 10^9\L: Cell per litre. %: Percentage. ‡: Higher than the other time points. : Lower than the other time points. †: Higher than the Before time point. A: Higher than the other groups. B: Higher than the circum-PHV group. C: Higher than the Adult group. Statistical analysis: Repeated measures ANOVA with Bonferroni post-hoc tests. d: Effect size by d-Cohen.

Fig. 5

Comparisons between leukocyte subpopulation levels in relation to the different time points of the present study. (a,b) Lymphocytes. (c,d) Monocytes. (e,f) Neutrophils. 10^9\L: Cell per litre. %: Percentage. ‡: Higher than the other time points. : Lower than the other time points. †: Lower than the Before and After RSE time points. #: Lower than the Before and 2 h post RSE time points. A: Higher than the other groups. B: Lower than the other groups. C: Higher than the Before and 24 h post RSE time points. |---|: Differences between different time points. |-|: Differences between different groups, within the same time point. Statistical analysis: Repeated measures ANOVA with Bonferroni post-hoc tests. d: Effect size by d-Cohen.

Fig. 6

Comparisons between the levels of lymphocyte subpopulations in relation to the different time points of the present study. (a) B cell subpopulation. (b) T-helper cell subpopulation. (c) Cytotoxic cell subpopulation. A.U.F. arbitrary units of fluorescence. ‡: Higher than the other time points. : Lower than the other time points. †: Lower than the Before and After RSE time points. A: Higher than the other groups. B: Lower than the other groups. |---|: Differences between different time points. |-|: Differences between different groups, within the same time point. Statistical analysis: Repeated measures ANOVA with Bonferroni post-hoc tests. d: Effect size by d-Cohen.

Fig. 7

Comparisons regarding cytokine levels to verify changes in systemic immune function considering the different groups (Condition) and time points (Time) analyzed in the present study. (pg/mL): Picogram per milliliter. TNF-α: Tumor necrosis factor α. ‡: Higher than the other time points. : Lower than the other time points. A: Higher than the other groups. B: Lower than the other groups. H: Higher than the Before & 24 h post time points. I: Higher than the Before & 2 h post time points. J: Higher than the After-time points. |---|: Differences between different time points. |-|: Differences between different groups, within the same time point. Statistical analysis: Repeated measures ANOVA with Bonferroni post-hoc tests. d: Effect size by d-Cohen.