Serum Hormone Concentrations and Body Composition in Brazilian Air Force Cadets During Rainforest Survival Training

Abstract

ABSTRACT Background Physiological adaptations in military jungle survival training have not yet been studied. Knowledge about the relationship between the insulin-like growth factor type I (IGF-I)/insulin-like growth factor binding protein type 3 (IGFBP-3) system and survival activities in a jungle environment can improve readiness and prepare Brazilian Air Force cadets for this kind of battlefield. Our goal was to assess changes in body composition and serum concentrations of the IGF-I/IGFBP-3 system in Brazilian Air Force cadets during five-day Amazon rainforest survival training and whether differences in sex influence these variations. Methods In the five-day survival training, variations in body composition and serum levels of IGF-I and IGFBP-3 were observed. The sample consisted of 14 male cadets (21.71 ± 1.64 years) and 6 female cadets (22.00 ± 1.41 years). Changes were assessed before and immediately after the survival training. Results The male cadets’ body mass (pre: 73.89 ± 8.79 kg; post: 69.57 ± 8.44 kg), body fat (pre: 11.43 ± 4.15%; post: 10.16 ± 4.19%), IGF-I serum concentrations (pre: 252 ± 72 ng/mL; post: 140 ± 42 ng/mL), and IGFBP-3 serum concentrations (pre: 4.90 ± 0.67 ng/mL; post: 4.22 ± 0.73 ng/mL) were significantly reduced (P < .01). In the female cadets, the mean body mass values (pre: 60.98 ± 8.82 kg; post: 57.91 ± 9.01 kg), body fat (pre: 19.20 ± 5.03%; post: 17.19 ± 4.77%), and IGF-I serum concentrations (pre: 202 ± 50 ng/mL; post: 108 ± 29 ng/mL) also decreased significantly (P < .01) after survival training. Finally, the cadet’s sex does not affect the variations of IGF-I (P = .46) and IGFBP-3 (P = .205) serum concentrations. Conclusions These findings all suggest that changes in body mass and body fat, as well as variations in the IGF-I/IGFBP-3 system, corroborate the need for military readiness preparation. Equivalent changes in both sexes indicate probable equal recovery intervals after survival training.