Military field training exercise with prolonged physical activity and sleep restriction causes hormonal imbalance in firefighter cadets

Purpose To evaluate the impact of the “Search and rescue” field military training exercise (SR_FTX) on hormonal modulation and identify their possible correlation with physical and cognitive performance. Methods An observational (before and after) study was carried out, with male firefighters cadets ( n = 42; age = 23[22;27] years) undergoing a nine-day military exercise (SR_FTX). The Countermovement jump (physical performance), the Stroop test (cognitive alertness), and blood tests for testosterone, cortisol, GH, and IGF-1 were applied. Wilcoxon for paired samples and Spearman’s correlation tests were used. Results Testosterone (751.10 [559.10;882.8] vs. 108.40 [80.12;156.40] ng/dL) and IGF-1 (217.5 [180;239.30] vs. 105 [93;129] ng/mL) significantly decreased while GH (0.10 [0.06;0.18] vs. 1.10 [0.58;2.28] ng/mL) and cortisol (9.60 [8.20;11.55] vs. 15.55 [12.28;18.98] ug/dL) significantly increased. Physical performance (31.2 [30.04;35.4] vs. 21.49 [19,02;23,59] cm) and cognitive alertness were significantly worse after SR_FTX (Congruent task: 1,78 (0183) vs. 1,56 (0185) response/s and incongruous task: 1,23 (0191) vs. 1,02 (0207) response/s). The physical performance showed a strong correlation with testosterone (rho = 0.694) and regular correlations with both IGF-1 (rho = 0.598) and cortisol (rho = − 0.580). The Stroop test presented weak correlations with GH (rho = − 0.350) and cortisol (rho = − 0.361). Conclusion SR_FTX negatively impacted hormonal modulation, physical and cognitive performance. These findings could help commanders decide to replace the employed firefighters in a real mission more frequently. Also, if the real scenario allows, they could think about providing better work conditions, such as improving caloric intake and rest periods, to preserve the military performance and health.