Heart Rate Variability Recordings are a Valid Non- Invasive Tool for Evaluating Soldiers’ Stress

Heart Rate Variability Recordings are a Valid Non- Invasive Tool for Evaluating Soldiers’ Stress

The purpose of the present study was to investigate physiological responses and to evaluate heart rate variability as a non-invasive stress indicator during a 72-hour military field training (MFT). Ten healthy male soldiers (age 20 ± 1 yr.) participated in MFT. They slept approximately 2 h/day and ate only army field rations. During MFT, the soldiers’ mean (±SD) energy expenditure was 4646 ± 674, energy intake 2200 ± 326, and energy deficit (ED) 2405 ± 890 kcal⋅day-1.Throughout the entire training period, serum total testosterone (TES) reduced from 19.0 ± 3.0 to 12.6 ± 6.2 nmol⋅l-1 (p<0.001)