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Leukocyte response to repeated sprint exercise: Differences between adolescent and adult athletes
Paulo Francisco de Almeida-Neto1,2, Phelipe Wilde1, Gilmara Gomes de Assis3,4
1Health Sciences Center, Federal University of Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil.
Background:
Repeated sprint exercise (RSE) can significantly affecting leukocytes dynamics, influenced by fitness, lifestyle, and biological maturation (BM), especially in adolescents.
Methods:
This experimental trial examined RSE effects on leukocyte responses in 34 male-athletes (18 adolescents, age = [12.9 ± 1.1] years; 16 adults, age = [22.5 ± 2.2] years). Participants performed 3 sets of 6 sprints (35 m with 10 s of passive rest and 5 min between sets), with blood samples collected before, immediately after, 2 h, and 24 h after-RSE. Leukocyte levels were analyzed microscopically and via leukogram, and adolescents' BM was assessed using peak-height-velocity (PHV). Statistical analyses included Friedman and Mann-Whitney U tests.
Results:
Total leukocyte counts increased immediately after and at 2 h after-RSE in both groups (p < 0.001 56). Lymphocytes increased immediately after-RSE (absolute and relative, p < 0.001 56). Absolute segmented neutrophils and the neutrophil-to-lymphocyte-ratio (NLR) peaked at 2 h (p < 0.001). Large granular lymphocytes (LGLs) increased only immediately after-RSE (p < 0.001 56). Absolute and relative eosinophils decreased at 2 h and rose again 24 h (p < 0.001 56). Regarding the condition factor, 2 h after-RSE adults showed higher levels of NLR and segmented neutrophils compared to adolescents (p < 0.000 1); while adolescents were higher in relative lymphocyte values (p < 0.000 1). Eosinophil levels were higher in adolescents 2 h after-RSE, extending up to 24 h after-RSE (p < 0.000 1). In PHV-based sub-analyses, for the time factor, circum-PHV (circum = during-PHV) individuals showed more evident responses in total leukocytes, absolute lymphocytes, LGLs, and segmented neutrophils (p < 0.001 56), reflecting greater immunological sensitivity to exercise. No significant condition-related differences were observed between pre- and circum-PHV subgroups.
Conclusions:
It is concluded that RSE promotes transient immune mobilization, more pronounced in adults, and modulated by the stage of biological maturation.
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