Sex-Specific Immune Cell Mobilization and Recovery After High-Volume Glycolytic Squat Exercise

ABSTRACT: Kraemer, WJ, Mastro, AM, Saenz, C, Freidenreich, DJ, Volk, BM, Gomez, AL, Fragala, MS, Szivak, TK, Post, EM, Wolf, MR, Comstock, BA, Hakkinen, K, Newton, RU, and Volek, JS. Sex-specific immune cell mobilization and recovery after high-volume glycolytic squat exercise. J Strength Cond Res XX(X): 000-000, 2026-Acute resistance exercise precipitates a rapid immunological process for surveillance, host protection, and muscle regeneration. In this study, we examined sex-specific differences in leukocyte mobilization after a single bout of high-volume, glycolytic squat resistance exercise. Thirty-four men and 24 women, recreationally active but not resistance-trained, performed 6 sets of 10 repetitions of parallel-depth barbell squats at 65%-10RM on a Smith machine. Venous blood was collected pre-exercise, 15 minutes post, and 60 minutes post-]exercise. Flow cytometry was used to quantify total lymphocytes, T cells (CD3+), T helper (CD4+) and T cytotoxic (CD8+) subsets, B cells (CD19+), natural killer (NK) cells, early activation marker CD69 on multiple subsets, and T-cell regulatory markers CD25 and CD127. Men exhibited greater transient lymphocyte mobilization at 15 minutes postexercise than women (p < 0.05), driven largely by NK cell increases (more than twice the magnitude of women, p < 0.05). CD4+ counts increased in women at 60 minutes (p < 0.05). Both sexes demonstrated significant time-dependent declines in lymphocytes, B cells, and T cells by 60 minutes, with men showing greater modulation of activation markers CD69, CD25, and CD127. Effect sizes indicated moderate-to-very large changes in NK cells, lymphocytes, and T-cell subsets in men, and moderate-to-large changes in NK cells and lymphocytes in women. Moderate - intensity, high-volume resistance exercise elicits robust but partially sex-dependent leukocyte mobilization, particularly in NK cells and early activation markers. These findings highlight the influence of sex on acute immune responses to resistance exercise and the time course of leukocyte mobilization during early recovery.