Hormonal responses during a prolonged military field exercise with variable exercise intensity.
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 (TES(free), -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 TES(free) 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 (T(4)) 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 1,000 kcal/day.
Department of Biology of Physical Activity, University of Jyväskylä, 40114, Jyväskylä, Finland. heikki.kyrolainen@sport.jyu.fi
Heikki
H
Kyröläinen
Jari
J
Karinkanta
Matti
M
Santtila
Harri
H
Koski
Matti
M
Mäntysaari
Teemu
T
Pullinen
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D001810:Blood Volume / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D003402:Creatine Kinase / Q000097:blood; D002149:Energy Intake / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D006728:Hormones / Q000097:blood*; D006801:Humans; D008297:Male; D008889:Military Personnel
D001786:Blood Glucose; D006728:Hormones; D003402:Creatine Kinase