Cortisol and Testosterone Awakening Response During Training in Elite Military Men: 3487 Board #175 June 1 8:00 AM - 9:30 AM

Elite military training is highly stressful on the body and challenges the individual operator to maintain allostasis (i.e., the ability to adapt and recover from repetitive stressors). It is well understood that increased allostatic load, above that of allostasis, may lead to hormonal imbalances in the hypothalamic-pituitary adrenal (HPA) and gonadal (HPG) axes. However, it is not well understood if elite military training elevates allostatic load enough to disrupt the HPA and HPG axes. PURPOSE: To determine the cortisol awakening response (CAR)—an outcome metric of the HPA axis—and the testosterone awakening response (TAR)—an outcome metric of the HPG axis—over the course of a 9-month unit level training (ULT) cycle. METHODS: Active duty, elite, male operators (n = 37; age: 28.6 ± 3.8 yrs; height: 178.0 ± 5.3 cm; weight: 87.0 ± 8.6 kg) participated in this study. Operators were stratified into 3 groups based on age (20-26, 27-29, and 30-41 yrs). Daily self-administered saliva samples were completed by each operator at the time of Wake, Wake + 30 min, and Wake + 60 min, pre- and post-ULT cycle. All CAR and TAR data were calculated as area under the curve from the ground (AUCG). Differences and interactions between age groups and days were examined using a 3 (age) × 2 (day) mixed effects model. RESULTS: There was a significant interaction between age groups and days for CAR (p < .0001) and TAR (p < .0001) AUCG. Simple effects comparing differences in the CAR AUCG from operators aged 27-29 yrs exhibited a 22.8% decrease in CAR following ULT (AUCG: = 17.5 ± 8.3 vs. 13.6 ± 7.5, p = .01). Examination of the individual main effects revealed significant differences comparing age groups in TAR (p = .006). Adjusted contrast analysis revealed operators aged 20-26 yrs had a heightened TAR during both pre- and post-ULT time points when compared with those aged 27-29 yrs (AUCG: pre = 12059.8 ± 3819.0 vs. 8439.4 ± 3801.5; post = 11834.1 ± 5588.5 vs. 7754.2 ± 2606.3, p < .0001) and 30-41 yrs (AUCG: pre = 12059.8 ± 3819.0 vs. 8298.1 ± 3440.0; post = 11834.1 ± 5588.4 vs. 8640.4 ± 5087.7, p < .0001). CONCLUSION: Results indicate the middle-aged group (27-29 yrs) has a decrease in CAR over the 9-month ULT cycle compared with the younger and older age groups. Additionally, the youngest operators, aged 20-26 yrs, have the highest TAR, regardless of time point.