Effects of 36-hour recovery on marksmanship and hormone concentrations during strenuous winter military survival training

Abstract

Objectives: Survival training can provide a unique setting for scientific examination of human stress responses and physical performance in a realistic operational military context. The aim of the present study was to observe effects of a 36-h recovery period on serum hormone concentrations, salivary cortisol, and marksmanship during 10-day winter military survival training in north of the Arctic Circle.

Design and methods: Sixty-eight male soldiers were randomly divided into two groups; EXP (n = 26) and CON (n = 42). While CON performed the whole exercise phase in the field, EXP had 36-h recovery period between days 6 and 8. Several hormones were measured during the study to investigate recovery.

Results: Subjective physical and mental demand as well as catabolic hormone levels increased and anabolic hormones decreased in CON (p < 0.05), whereas in EXP, recovery period attenuated negative effects of survival training. Prone shooting performance decreased (87.5 ± 6.5 vs. 76.3 ± 8.8, points out of 100, p < 0.05) between days 6 and 8 in CON while EXP was able to maintain shooting performance throughout the study.

Conclusion: A short recovery during a strenuous training can prevent the degradation in psychophysiological state and shooting performance in soldiers, which can be crucial for survival in demanding operational winter environment. In the present study, 36-h rest period during the field training seems to enhance recovery but the duration of the period was inadequate for full recovery from the accumulated operative stress. In conclusion, appropriate recovery periods should be implemented in order to optimize occupational performance during high operative stress.

Keywords: Arctic; Endocrinology; SERE; Soldier.

Fig. 1

Study design. PRE = pre-measurement, MID1 = before recovery phase, MID2 = after recovery phase

Fig. 2

Daily RPE (rate of perceived exertion), sleep, mental and physical demands, and saliva cortisol (sCOR) AM and PM values during SERE in both EXP and CON groups. D and E = p < 0.05 compared to day 1 value, # = difference between groups p < 0.05. Experimental period is highlighted with dashed line

Fig. 3

Serum biomarker profiles during the study. COR = cortisol; TES = testosterone; SHBG = sex hormone-binding globulin; IGF-1 = insulin-like growth factor 1; CK = creatine kinase; DHEA-S = dehydroepiandrosterone sulfate; EPI = epinephrine; NOR = norepinephrine. A = p < 0.05 compared to PRE, B = p < 0.05 compared to MID1, C = p < 0.05 compared to MID2, # = difference between groups p < 0.05. Experimental period is highlighted with dashed line