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.

The present study shows that the increase in mean body mass of young male conscripts has slowed down during the last 10 yr. However, their aerobic capacity has still decreased during recent decades. In addition, the proportion of conscripts with poor muscle fitness has increased. From the national defense and health perspective, more initiatives are needed to encourage young men to increase their level of daily physical activity to be fit and ready for operations.

Background: There are only a few studies that have assessed awareness and knowledge regarding aerobic type of physical activity (PA) guidelines recommendations, while no previous studies have examined muscular type of activity recommendation guidelines. The aim was to assess knowledge and awareness and study the associations with demographic variables and physical activity and fitness.Methods: Participants were 776 young (age 26 ± 7 years) men. Awareness and knowledge of PA recommendation guidelines were assessed by prompted questionnaires together with demographic variables and physical activity. In addition, physical fitness was measured.Results: Forty percent of the participants reported being aware of the physical activity recommendation. Moreover, 7% correctly identified the recommendations for moderate aerobic physical activity and 25% for muscular type of activity. In addition, 4% correctly identified both aerobic and muscular activity recommendations. Being aware of the PA recommendations was associated with being married or partnered, having higher education level and being more physically active during leisure-time (p < 0.05). Individuals with no awareness of the recommendations had lower results in cardiorespiratory and muscular fitness compared to those being aware (p < 0.05). Being married or partnered was positively associated with the knowledge of the muscular activity recommendations (p < 0.05). Moreover, the individuals with correct knowledge of the PA recommendations had higher levels of muscular fitness (p < 0.05).Conclusion: A low number of individuals are aware or know the physical activity recommendations among young adult men. Therefore, more vigorous attempts to promote physical activity recommendations are needed.

The effect of 60-h sleep deprivation (SD) on physical performance and motor control was studied. Twenty cadets were measured for aerobic performance (VO2) before and immediately after the SD period. Maximal strength and EMG of the knee extensor muscles were measured before and after 60 h of SD. Balance, reaction times and motor control were assessed every evening and morning during the SD period. Main effects were observed for heart rate (p = 0.002, partial eta squared: 0.669), VO2 (p = 0.004, partial eta squared: 0.621), ventilation (p = 0.016, partial eta squared: 0.049), and lactate concentration (p = 0.022, partial eta squared: 0.501), whereas RER remained unaltered (p = 0.213, partial eta squared: 0.166). Pairwise comparisons revealed decreased values at submaximal loads in heart rate, VO2, ventilation (all p < 0.05) but not in RER, whereas all of their respective maximal values remained unchanged. Moreover, pairwise comparisons revealed decreased lactate concentration at maximal performance but only at 8-min time point during submaximal workloads (p < 0.05). Pairwise comparisons of maximal strength, EMG and rate of force development revealed no change after SD. Main effects were observed for motor and postural control, as well as for reaction times (all p < 0.05), whereas pairwise comparison did not reveal a consistent pattern of change. In conclusion, motor control can mostly be maintained during 60-h SD, and maximal neuromuscular and aerobic performances are unaffected. However, submaximal cardiorespiratory responses seem to be attenuated after SD.

In conclusion, the present study revealed that an increasing proportion of female recruits are overweight and/or have poor endurance performance, which are known risk factors for musculoskeletal injuries and premature discharge from military service. Therefore, specialized training programs should be designed specifically for female recruits with lower levels of fitness prior to military service.