Serum Hormones in Soldiers After Basic Training: Effect of Added Strength or Endurance Regimens

Abstract

Military personnel are often exposed to training programs and operational situations that involve multiple stressors such as caloric deficit, sleep deprivation, and prolonged physical effort, which may disturb body homeostasis, as indicated by hormonal responses.Therefore, we investigated the effects of three training regimens on serum basal hormone concentrations before and after the 8-wk basic training (BT) period, and whether possible changes in serum basal concentrations are related to changes in endurance and strength performance. Serum hormone levels were measured in 3 groups of 24 male military conscripts before and after 3 different types of training programs: normal basic training (NT); BT with added strength training (ST); and BT with added endurance training (ET). ET and ST increased their maximal strength by 12.9% and 9.1%, respectively, and their VO2max increased by 12.0% and 8.5%, but the changes did not differ significantly between the groups. Increases in serum basal testosterone concentration were observed in all groups (BT by 16.6%, ST by 16.3%, and ET by 26.6%). Serum basal cortisol concentration increased in ST by 11.1%. Serum basal thyroxine concentration decreased by 9.2% in NT, 11.9% in ST, and 10.5% in ET. The increases in strength, aerobic capacity, and testosterone after training indicate that the regimens were adequate to create positive training responses, especially in the ST and ET groups. On the other hand, unexpectedly low strength gains in the ST group during BT may be a consequence of too high an amount of endurance-based military training.