Energy Balance, Hormonal Status, and Military Performance in Strenuous Winter Training

Tarja Nykänen (), Tommi Ojanen, Jani P. Vaara, Kai Pihlainen, Risto Heikkinen, Heikki Kyröläinen and Mikael Fogelholm
Additional contact information
Tarja Nykänen: Army Academy, Finnish Defence Forces, 53600 Lappeenranta, Finland
Tommi Ojanen: Finnish Defence Research Agency, Finnish Defence Forces, 04310 Tuusula, Finland
Jani P. Vaara: Department of Leadership and Military Pedagogy, National Defence University, Finnish Defence Forces, 00861 Helsinki, Finland
Kai Pihlainen: Defence Command, Finnish Defence Forces, 00130 Helsinki, Finland
Risto Heikkinen: Statistical Analysis Services, Analyysitoimisto Statisti Oy, 40720 Jyväskylä, Finland
Heikki Kyröläinen: Department of Leadership and Military Pedagogy, National Defence University, Finnish Defence Forces, 00861 Helsinki, Finland
Mikael Fogelholm: Department of Food and Nutrition, University of Helsinki, 00014 Helsinki, Finland

IJERPH, 2023, vol. 20, issue 5, 1-12

Abstract: Severe energy deficit may impair hormonal regulation and physical performance in military trainings. The aim of this study was to examine the associations between energy intake, expenditure, and balance, hormones and military performance during a winter survival training. Two groups were studied: the FEX group ( n = 46) had 8-day garrison and field training, whereas the RECO group ( n = 26) had a 36-h recovery period after the 6-day garrison and field training phase. Energy intake was assessed by food diaries, expenditure via heart rate variability, body composition by bioimpedance, and hormones by blood samples. Strength, endurance and shooting tests were done for evaluating military performance. PRE 0 d, MID 6 d, POST 8 d measurements were carried out. Energy balance was negative in PRE and MID (FEX −1070 ± 866, −4323 ± 1515; RECO −1427 ± 1200, −4635 ± 1742 kcal·d −1 ). In POST, energy balance differed between the groups (FEX −4222 ± 1815; RECO −608 ± 1107 kcal·d −1 ( p < 0.001)), as well as leptin, testosterone/cortisol ratio, and endurance performance ( p = 0.003, p < 0.001, p = 0.003, respectively). Changes in energy intake and expenditure were partially associated with changes in leptin and the testosterone/cortisol ratio, but not with physical performance variables. The 36-h recovery restored energy balance and hormonal status after strenuous military training, but these outcomes were not associated with strength or shooting performance.

Keywords: energy deficit; physical performance; survival training; soldier (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2023
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