Abstract
The purpose of the present study was to test the hypothesis that the magnitude of hormonal concentration alterations during a prolonged military field exercise with constant energy intake (EI) is influenced by changes in energy deficit (ED) induced by varying the exercise intensity. Basal serum hormone concentrations were measured in a group of healthy young male volunteers (n = 7) during a 20-day field exercise. During the first week of the exercise, the average ED was 4,000 kcal/day (P-I), in the second week only 450 kcal/day (P-II), and in the last week 1,000 kcal/day (P-III). During the first 5 days of the field exercise, significant increases in cortisol (COR, +32%) and growth hormone (GH, +616%) concentrations were observed, while insulin (INS, −70%), total testosterone (TES, −27%), free testosterone (TESfree, −26%) decreased. However, after these initial responses, COR and GH returned to the pre-exercise level by the beginning of P-II. Also TES and TESfree recovered to the pre-exercise level by the beginning of P-III, and INS by the end of P-III. The concentration of TES (+29%) increased above the pre-exercise level by the beginning of P-III. Serum thyroxin (T4) concentration was significantly lesser (−12%) and urine urea concentration significantly higher (+78%) after the field exercise than before it. Therefore, it can be concluded that the lower levels of ED in the second and third phase (ED <1,000 kcal/day) allowed recovery of hormonal changes observed in the first phase with ED much greater than 1000 kcal/day.
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The authors would like to express their gratitude to the Finnish Defense Forces for financially supporting the study. Furthermore, we wish to thank all the subjects who volunteered for the study
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Kyröläinen, H., Karinkanta, J., Santtila, M. et al. Hormonal responses during a prolonged military field exercise with variable exercise intensity. Eur J Appl Physiol 102, 539–546 (2008). https://doi.org/10.1007/s00421-007-0619-0
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DOI: https://doi.org/10.1007/s00421-007-0619-0