Changes in energy balance, body composition, metabolic profile and physical performance in a 62-day Army Ranger training in a hot-humid environment

Effects of male paratroopers' initial body composition on changes in physical performance and recovery during a 20-day winter military field training

Changes in physiological markers and physical performance in relation to paratroopers' initial body composition were investigated during a 20-day winter military field training (MFT) and the subsequent 10-day recovery period. Body composition, serum hormone concentrations and enzymatic biomarkers, and physical performance of 58 soldiers were measured before, during, and after MFT. Comparisons were done according to soldiers' body fat percentage before MFT between low-fat (<12% body fat) and high-fat (>12% body fat) groups. Correlations between body fat percentage preceding MFT and changes in muscle mass, physical performance, and serum hormone concentrations and enzymatic biomarkers were investigated. It was hypothesized that soldiers with a higher fat percentage would have smaller decrements in muscle mass, physical performance, and serum testosterone concentration. The change in muscle and fat mass was different between groups (p < 0.001) as the low-fat group lost 0.8 kg of muscle mass and 2.0 kg of fat mass, while there was no change in muscle mass and a loss of 3.7 kg of fat mass in the high-fat group during MFT. Fat percentage before MFT correlated with the changes in muscle mass (R2 = 0.26, p < 0.001), serum testosterone concentration (R2 = 0.22, p < 0.001), and evacuation test time (R2 = 0.10, p < 0.05) during MFT. The change in muscle mass was correlated with the changes in evacuation test time (R2 = 0.11, p < 0.05) and countermovement jump test results (R2 = 0.13, p < 0.01) during MFT. Soldiers with a higher initial fat percentage lost less muscle mass, and had smaller decrements in some aspects of physical performance, as well as in serum testosterone concentration during MFT.

Narcissism Is Not Associated With Success in U.S. Army Soldier Training

INTRODUCTION

Narcissism has been studied for its role in leadership using various versions of the Narcissistic Personality Inventory (NPI). Narcissism is described as having a "dark and negative" side as well as a "positive or bright" side. The bright side of narcissism, in particular, has been studied for its role in leadership. In studies among military personnel in Finland and Hungary, the NPI has been associated with positive leadership traits. We assessed if measures of narcissistic personality were predictive of entrance to and graduation from the Army Ranger Course among United States (U.S.) Army personnel.

MATERIALS AND METHODS

We included the NPI as one of the measures in the Ranger Resilience and Improved Performance on Phospholipid-bound Omega-3's (RRIPP-3) study. RRIPP-3 was a double-blind, placebo-controlled dietary supplement intervention trial at Fort Benning, GA, that enrolled 555 officers when they entered the U.S. Army Infantry Basic Officer Leadership Course (IBOLC) with the intention to complete the U.S. Ranger School. RRIPP-3 volunteer participants consumed eight dietary supplements daily containing 2.3 g of omega-3 (krill oil) or macadamia nut oil (control) over a 20-week period. Blood spot samples were collected to monitor intake compliance. Cognitive functioning, resilience, and mood were assessed at approximately 14 and 16 weeks. Dietary intake was also assessed. The 40-item, forced-choice NPI was included to assess if three factors of narcissism: Leadership/Authority, Grandiose/Exhibitionism, and Entitlement/Exploitativeness measures of narcissistic personality were associated with entrance to and graduation from the Army Ranger Course.

RESULTS

Of the 555 soldiers enrolled in RRIPP-3, there were no statistically significant differences in the total NPI scores comparing U.S. Army IBOLC officers who enrolled (n = 225) versus did not enroll (n = 330, p = .649) or graduated (n = 95; versus did not graduate [n = 460, p = .451]) from the Ranger Course. None of the three-factor NPI subscales differed statistically comparing either enrollment in (p = .442, .510, and .589, respectively) or graduation from the Ranger Course (p = .814, .508, and .813, respectively).

CONCLUSIONS

Although narcissism has been positively associated with military trainee success in other countries, we did not find an association between narcissism and trainee success among U.S. Army trainees, and accordingly the level of narcissism did not predict trainee success or failure.

Comparison of Physical Fitness, Self-Assessed Resilience, and Self-Assessed Character Traits between Elite Polish Obstacle Course Racers and Polish Special Operations Force Personnel

INTRODUCTION

Some of the obstacle Course Race (OCR) competitions are co-organized by military units that are seeking candidates for service in special operations forces (SOFs). The aim of the study was to compare psycho-physical characteristics between Polish OCR athletes and SOF soldiers, in order to assess the possibility of recruiting future SOF soldiers from the OCR community.

MATERIALS AND METHODS

The study included 23 OCR competitors, and 17 soldiers from JW Formoza were used as the comparative group. The psychological measure of resilience was assessed using the Connor-Davidson Resilience Scale. Participants also completed a survey in which they had to rank character strengths. Physical fitness was assessed on the basis of a 3000-m run and the maximum number of sit-ups and straight pull-ups.

RESULTS

There were significant differences between OCR participants and JW Formoza soldiers: body mass index, 24.1 ± 1.5 vs. 25.9 ± 1.9 (P = .002); 3000-m run, 11:59 ± 0:49 vs. 12:11 ± 0:28 (P = .024); and straight pull-ups, 19 ± 3 vs. 15 ± 3 (P = .001). The most commonly chosen character strengths in both groups were self-control, team worker, and optimism.

CONCLUSIONS

OCR competitors show psychophysical characteristics similar to those expected from actual SOF personnel.

Exertional heat stroke: nutritional considerations

NEW FINDINGS

What is the topic of this review? The potential role of nutrition in exertional heat stroke. What advances does it highlight? Certain nutritional and dietary strategies used by athletes and workers may exert a protective effect the pathophysiological processes of exertional heat stroke, whereas others may be detrimental. While current evidence suggests that some of these practices may be leveraged as a potential countermeasure to exertional heat stroke, further research on injury-related outcomes in humans is required.

ABSTRACT

Exertional heat stroke (EHS) is a life-threatening illness and an enduring problem among athletes, military servicemen and -women, and occupational labourers who regularly perform strenuous activity, often under hot and humid conditions or when wearing personal protective equipment. Risk factors for EHS and mitigation strategies have generally focused on the environment, health status, clothing, heat acclimatization and aerobic conditioning, but the potential role of nutrition is largely underexplored. Various nutritional and dietary strategies have shown beneficial effects on exercise performance and health and are widely used by athletes and other physically active populations. There is also evidence that some of these practices may dampen the pathophysiological features of EHS, suggesting possible protection or abatement of injury severity. Promising candidates include carbohydrate ingestion, appropriate fluid intake and glutamine supplementation. Conversely, some nutritional factors and low energy availability may facilitate the development of EHS, and individuals should be cognizant of these. Therefore, the aims of this review are to present an overview of EHS along with its mechanisms and pathophysiology, discuss how selected nutritional considerations may influence EHS risk focusing on their impact on the key pathophysiological processes of EHS, and provide recommendations for future research. With climate change expected to increase EHS risk and incidence in the coming years, further investigation on how diet and nutrition may be optimized to protect against EHS would be highly beneficial.