Hormonal and inflammatory responses to high-intensity functional training in male soldiers

This study investigated the effects of high-intensity functional training (HIFT) on hormonal and inflammatory biomarker responses during military service. One hundred and twenty-seven male conscripts were assessed over a 19-week training period. The experimental group (EXP: n = 64) followed a structured HIFT program, while the control group (CON: n = 63) adhered to conventional military physical training. Blood samples were collected at baseline (PRE), week 10 (MID), and post-intervention (POST) to measure serum testosterone, cortisol, testosterone/cortisol ratio, insulin-like growth factor 1 (IGF-1), sex hormone-binding globulin (SHBG), high-sensitivity C-reactive protein (hs-CRP), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α). Body composition and physical performance were also measured. Serum testosterone increased in both groups between PRE and POST (EXP: +3.3 ± 3.8 nmol·L^-1, p < 0.001; CON: +3.7 ± 3.4 nmol·L^-1, p < 0.001), while cortisol remained unchanged. Testosterone/cortisol ratio increased in both groups (+0.010 ± 0.010, p < 0.001 for both). IGF-1 increased in CON (+4.4 ± 5.9 nmol·L^-1, p < 0.001) and SHBG increased in EXP (+3.1 ± 9.0 nmol·L^-1, p = 0.005). Inflammatory biomarkers (hs-CRP, IL-6) decreased in both groups. No adverse biomarker responses were observed, suggesting that HIFT was well tolerated during military service.