Abstract / Summary
Abstract Background Rapid weight loss (RWL) is commonly used by wrestlers to qualify for lower weight categories, but the combined effects of RWL and intense exercise on circulating immune cell profiles, particularly lymphocyte subsets, remain incompletely characterized. This study examined the effects of a 5-day RWL period (4.3% body weight reduction) on complete blood count and lymphocyte subsets in highly trained national-level male wrestlers. Methods Nine national-level male wrestlers (age: 21.7 ± 3.6 years) underwent two experimental phases: (1) exercise-only (before weight loss), with blood samples collected before (PRE1) and immediately after (PRE2) a standardized exercise protocol; and (2) exercise combined with 5-day RWL (4.3% body weight loss), with blood samples collected before (POST1) and after (POST2) the same exercise protocol. Complete blood count parameters were analyzed using an automated hematology analyzer, and lymphocyte subsets (CD3+, CD4+, CD8+, CD19+, CD16/56+) were assessed by flow cytometry. Data were analyzed using paired t-tests and Wilcoxon signed-rank tests. Paired effect sizes were expressed as Cohen’s dz, Wilcoxon effect sizes as r = Z/√N, with 95% confidence intervals for all mean differences; a condition × time interaction (change-score) analysis and Benjamini–Hochberg FDR correction were applied. Results Acute exercise before RWL increased white-blood-cell count (7.11 → 9.91 × 10³/µL; +2.80 [95% CI 1.61, 3.99]; p = 0.004), neutrophil count ( p = 0.001), platelet count ( p = 0.004) and plateletcrit ( p = 0.007); all survived FDR correction. Following the 5-day RWL period, participants showed a lower resting absolute lymphocyte count (2.02 → 1.40 × 10³/µL; ≈31% reduction; p = 0.008) and lower resting haemoglobin and haematocrit. After RWL, exercise increased absolute CD3+, CD8 + and CD3 + CD8+ T-cell counts ( p = 0.012–0.023); however, a formal condition × time interaction test showed these exercise responses did not differ significantly from the pre-RWL condition (interaction p ≥ 0.44), and no CBC interaction survived FDR correction. Small decreases in haemoglobin and MCV after exercise in the post-RWL phase were nominal only and of uncertain clinical significance. Conclusions In this small exploratory sample, a 5‑day RWL period of 4.3% body weight reduction was associated with alterations in hematological parameters and lymphocyte subsets. Following the 5-day RWL period, reduced resting lymphocyte counts were observed, while exercise after RWL was associated with increases in absolute cytotoxic T‑cell counts. Small acute decreases in hemoglobin and MCV were observed following exercise after RWL. These preliminary findings highlight the need for careful weight management strategies and further research to determine the clinical significance of these changes. Trial registration ClinicalTrials.gov NCT07567937. Registered 22 April 2026.