Effects of testosterone enanthate on aggression, risk-taking, competition, mood, and other cognitive domains during 28 days of severe energy deprivation.

RATIONALE: Behavioral effects of testosterone depend on dose, acute versus sustained formulation, duration of administration, personality, genetics, and endogenous levels of testosterone. There are also considerable differences between effects of endogenous and exogenous testosterone. OBJECTIVES: This study was the secondary behavioral arm of a registered clinical trial designed to determine if testosterone protects against loss of lean body mass and lower-body muscle function induced by a severe energy deficit typical of sustained military operations. METHODS: Behavioral effects of repeated doses of testosterone on healthy young men whose testosterone was reduced by severe energy deficit were examined. This was a double-blind, placebo-controlled, between-group study. Effects of four weekly intramuscular injections of testosterone enanthate (200 mg/week, N = 24) or matching placebo (N = 26) were evaluated. Determination of sample size was based on changes in lean body mass. Tasks assessing aggression, risk-taking, competition, social cognition, vigilance, memory, executive function, and mood were repeatedly administered. RESULTS: During a period of artificially induced, low testosterone levels, consistent behavioral effects of administration of exogenous testosterone were not observed. CONCLUSIONS: Exogeneous testosterone enanthate (200 mg/week) during severe energy restriction did not reliably alter the measures of cognition. Study limitations include the relatively small sample size compared to many studies of acute testosterone administration. The findings are specific to healthy males experiencing severe energy deficit and should not be generalized to effects of other doses, formulations, or acute administration of endogenous testosterone or studies conducted with larger samples using tests of cognitive function designed to detect specific effects of testosterone.

Effects of energy balance on cognitive performance, risk-taking, ambulatory vigilance and mood during simulated military sustained operations (SUSOPS).

Sustained operations (SUSOPS) require military personnel to conduct combat and training operations while experiencing physical and cognitive stress and limited sleep. These operations are often conducted in a state of negative energy balance and are associated with degraded cognitive performance and mood. Whether maintaining energy balance can mitigate these declines is unclear. This randomized crossover study assessed the effects of energy balance on cognitive performance, risk-taking propensity, ambulatory vigilance, and mood during a simulated 72-h SUSOPS. METHODS: Ten male Soldiers (mean ± SE; 22.4 ± 1.7 y; body weight 87.3 ± 1.1 kg) completed two, 72-h simulated SUSOPS in random order, separated by 7 days of recovery. Each SUSOPS elicited ∼4500 kcal/d total energy expenditure and restricted sleep to 4 h/night. During SUSOPS, participants consumed either an energy-balanced or restricted diet that induced a 43 ± 3% energy deficit. A cognitive test battery was administered each morning and evening to assess: vigilance, working memory, grammatical reasoning, risk-taking propensity, and mood. Real-time ambulatory vigilance was assessed each morning, evening, and night via a wrist-worn monitoring device. RESULTS: Participants exhibited heightened risk-taking propensity (p = 0.047) with lower self-reported self-control (p = 0.021) and fatigue (p = 0.013) during energy deficit compared to during energy balance. Vigilance accuracy (p < 0.001) and working memory (p = 0.040) performance decreased, and vigilance lapses increased (p < 0.001) during SUSOPS, but did not differ by diet. Percentage of correct responses to ambulatory vigilance stimuli varied during SUSOPS (p = 0.019) independent of diet, with generally poorer performance during the morning and night. Total mood disturbance (p = 0.001), fatigue (p < 0.001), tension (p = 0.003), and confusion (p = 0.036) increased whereas vigor decreased (p < 0.001) during SUSOPS, independent of diet. CONCLUSION: Prolonged physical activity combined with sleep restriction is associated with impaired vigilance, memory, and mood state. Under such conditions, maintaining energy balance prevents increased risk-taking and improves self-control, but does not improve other aspects of cognitive function or mood. Given the small sample in the present study, replication in a larger cohort is warranted.

A Z-score based method for comparing the relative sensitivity of behavioral and physiological metrics including cognitive performance, mood, and hormone levels.

A method for assessing the relative sensitivity of research metrics is proposed and illustrated by comparing 18 outcome measures from a published study of the cognitive, mood, and hormonal effects of four different levels of stress induced by intense military training. Research on the human response to stress often assesses multiple disparate dependent measures. Selecting the most sensitive is difficult as formal methods to compare varied dependent measures have not been developed. The method first converts the outcome measures into standard scores (z-scores) and then compares them using analysis of variance to determine whether there are differences in how they assess the impact of graded levels of exposure to stress. The analysis detected various significant interactions in several measures and suggests self-report mood questionnaires were more sensitive to the stressors present in the study than the cognitive or hormonal measures which were used. These findings support the effectiveness of the z-score based method as a useful procedure for objectively evaluating the differential sensitivity of various metrics. This method could be useful for research on other independent variables when use of multiple assessment strategies is appropriate. It could be used for evaluating studies yielding conflicting results, such as those detecting effects on one parameter but not others. In such instances, cross-metric inconsistencies may be due to differential sensitivity of measurement strategies rather than actual differences in the effects of the independent-variable on the domains under investigation.

Field assessment and enhancement of cognitive performance: development of an ambulatory vigilance monitor.

INTRODUCTION: Limited opportunities to study human cognitive performance in non-laboratory, ambulatory situations exist. However, advances in technology make it possible to extend behavioral assessments to the field. One of the first devices to measure human behavior in the field was the wrist-worn actigraph. This device acquires minute-by-minute information on an individual's physical activity and can distinguish sleep from waking, the most basic aspect of behavior. METHODS: Our laboratory developed a series of wrist-worn devices, not much larger than a watch, which assess reaction time, vigilance and memory. The devices concurrently assess motor activity with greater temporal resolution than standard actigraphs. They also continuously monitor multiple environmental variables including temperature, humidity, sound, and light. RESULTS: These monitors have been employed during training and simulated military operations to collect behavioral and environmental information that would typically be unavailable under such circumstances. Development of the vigilance monitor, and how each successive version extended capabilities of the device are described. Data from several studies are presented, including studies conducted in harsh field environments during a simulated infantry assault, an officer training course. DISCUSSION: The monitors simultaneously documented environmental conditions, patterns of sleep and activity and effects of nutritional manipulations on cognitive performance. They provide a new method to relate cognitive performance to real world environmental conditions and assess effects of various interventions on human behavior in the field. They can also monitor cognitive performance in real time, and if it is degraded, attempt to intervene to maintain

Adherence to the Dietary Guidelines for Americans Is Associated with Psychological Resilience in Young Adults: A Cross-Sectional Study.

BACKGROUND: The 2010 Healthy Eating Index (HEI-2010), a measure of diet quality, is used to quantify adherence to the Dietary Guidelines for Americans. Better HEI scores have been associated with positive health outcomes; however, the relationship between diet quality and psychological resilience, a mental health attribute for coping with adversity, has not been assessed. OBJECTIVE: The objective of the present study was to assess the relationship between diet quality and psychological resilience, and the relationship between resilience and demographics, anthropometrics, socioeconomic status, and health behavior. DESIGN: In this cross-sectional study, HEI-2010 scores and resilience were assessed using the Block food frequency questionnaire and the Connor-Davidson Resilience Scale. Other factors that can affect the relationship between HEI-2010 scores and resilience were assessed using surveys, and height and weight were measured to calculate body mass index. PARTICIPANTS/SETTING: Male and female Army and Air Force recruits (n=834) enrolled in a randomized controlled trial and 656 (mean±standard deviation [SD] age=21±3.3 years) were included in this analysis. Data were collected before the initiation of military training at Fort Sill, OK (2012-2013) and Lackland Air Force Base, TX (2013-2014). STATISTICAL ANALYSIS PERFORMED: Participants were split into low- and high-resilience groups based on Connor-Davidson Resilience Scale scores. Student's t test and χ2 tests were used to determine differences between groups for continuous and categorical variables, respectively. Logistic regression was utilized to identify predictors of resilience. RESULTS: Better diet quality was associated with resilience; higher HEI predicted an increased likelihood (odds ratio=1.02; 95% CI 1.01 to 1.04) of a participant being in the high-resilience group after including race, ethnicity, education, smoking, age, body mass index, sex, and military branch in the full model. The data indicate that with every 10-point increase in HEI score, there was a 22% increased likelihood of being in the high-resilience group. CONCLUSIONS: Registered dietitian nutritionists should continue to encourage attainable changes to improve diet; study data suggest that small improvements in diet quality can be associated with better psychological resilience.

Cognition during sustained operations: comparison of a laboratory simulation to field studies.

INTRODUCTION: Military operations, especially combat, expose individuals to multiple stressors, including sleep loss, food deprivation, and sustained physical activity. Civilians, such as woodland firefighters, disaster victims, and relief workers, are also exposed to such environments. Our laboratory developed a brief, intense, laboratory-based simulation of a multistressor environment which included sleep loss, continuous physical activity, and food deprivation. METHODS: During this sustained operations (SUSOPS) scenario, and a control period, cognitive performance and mood were measured in 13 volunteers. The scenario included road marches, battle drills, and land navigation. Physical activity and sleep were assessed with actigraphs. RESULTS: Significant decrements in visual vigilance, choice reaction time, and matching-to-sample, a test of short-term memory, were observed. Marksmanship was stable and physical activity significantly increased. Mood states assessed by the Profile of Mood States (POMS: Tension, Depression, Anger, Vigor, Fatigue and Confusion) also significantly deteriorated. DISCUSSION: Cognitive function declined more extensively and rapidly than physical performance. Decrements in cognitive performance were comparable to those in a field study conducted for an equivalent period of time in uncontrolled conditions. This demonstrates that decrements in cognitive function and increased physical activity, similar to those in highly stressful field environments, can be duplicated under controlled conditions. The simulated SUSOPS scenario is an appropriate paradigm for assessment of adverse effects of military and civilian multistressor environments on human performance, physiology, and interventions designed to mitigate them.

Cognitive function, stress hormones, heart rate and nutritional status during simulated captivity in military survival training.

Stress influences numerous psychological and physiological processes, and its effects have practical implications in a variety of professions and real-world activities. However, few studies have concurrently assessed multiple behavioral, hormonal, nutritional and heart-rate responses of humans to acute, severe stress. This investigation simultaneously assessed cognitive, affective, hormonal, and heart-rate responses induced by an intensely stressful real-world environment designed to simulate wartime captivity. Sixty males were evaluated during and immediately following participation in U.S. Army Survival, Evasion, Resistance, and Escape (SERE) school, three weeks of intense but standardized training for Soldiers at risk of capture. Simulated captivity and intense mock interrogations degraded grammatical reasoning (p<0.005), sustained-attention (p<0.001), working memory (p<0.05) and all aspects of mood assessed by the Profile of Mood States (POMS) questionnaire: Tension/Anxiety, Depression/Dejection, Anger/Hostility, Vigor/Activity, Fatigue/Inertia; Confusion/Bewilderment, and Total Mood Disturbance (p<0.001) It also elevated heart rate (p<0.001); increased serum and salivary cortisol and dehydroepiandrosterone-sulfate (DHEA-s) (p<0.01); elevated serum epinephrine, norepinephrine, and soluble transferrin receptors (sTfR) (p<0.01); increased salivary neuropeptide-Y (NPY) (p<0.001); and decreased serum prolactin and serum and salivary testosterone (p<0.001). Partial recovery was observed immediately after training, but stress-induced changes, particularly in body weight and several of the biomarkers, persisted. This study demonstrates that when individuals were exposed to realistic and controlled simulated captivity, cognition, mood, stress hormones, nutritional status and heart rate are simultaneously altered, and each of these subsequently recovers at different rates.

Severe decrements in cognition function and mood induced by sleep loss, heat, dehydration, and undernutrition during simulated combat.

BACKGROUND: Military exercises generate high levels of stress to simulate combat, providing a unique opportunity to examine cognitive and physiologic responses of normal humans to acute stress. METHODS: Cognitive and physiologic markers of stress were evaluated before, during, and after an intense training exercise conducted for 53 hours in the heat. Cognitive performance, mood, physical activity, sleep, body composition, hydration, and saliva cortisol, testosterone, and melatonin were assessed. Volunteers were 31 male U.S. Army officers from an elite unit, aged 31.6 +/- .4 years. RESULTS: Wrist activity monitors documented that soldiers slept only 3.0 +/- .3 hours during the exercise and were active throughout. Volunteers lost 4.1 +/- .2 kg (p < .001) of weight, predominately water (3.1 +/- .3 L) (p < .001). Substantial degradation in cognitive function, assessed with computerized tests, occurred. Vigilance, reaction time, attention, memory, and reasoning were impaired (p < .001). Mood, including vigor (p < .001), fatigue (p < .001), confusion (p < .001), depression (p < .001), and tension (p < .002), assessed by questionnaire, deteriorated. The highest cortisol and testosterone levels were observed before the exercise. CONCLUSIONS: This study quantifies the overwhelmingly adverse impact of multiple stressors on cognitive performance, mood, and physiologic parameters, during a continuous but brief military exercise conducted by highly motivated, well-trained officers.

The fog of war: decrements in cognitive performance and mood associated with combat-like stress.

INTRODUCTION: Anecdotal reports from military conflicts suggest cognitive performance and mood are severely degraded by the stress of combat. However, little objective information is available to confirm these observations. METHODS: Our laboratory had several unique opportunities to study cognitive function in warfighters engaged in exercises designed to simulate the stress of combat. These studies were conducted in different environments with two different types of military volunteers. In one study, subjects were officers, with an average 9 yr of military service, who were members of an elite U.S. Army unit, the Rangers. In the other study, participants were younger, mostly enlisted, trainees with only 3 yr of military experience on average, in training to determine if they would qualify for an elite U.S. Navy unit, the SEALS. We administered a variety of identical, computer-based cognitive tests to both groups. RESULTS: In both groups, during stressful combat-like training, every aspect of cognitive function assessed was severely degraded compared with baseline, pre-stress performance. Relatively simple cognitive functions such as reaction time and vigilance were significantly impaired, as were more complex functions, including memory and logical reasoning. DISCUSSION: The deficits observed were greater than those typically produced by alcohol intoxication, treatment with sedating drugs, or clinical hypoglycemia. Undoubtedly, such decrements would severely degrade operational effectiveness. Furthermore, it is likely such cognitive decrements would be greater during actual combat. War planners, doctrine developers, and warfighters, especially leaders, need to be aware that combat stress will result in extensive and severe deficits in cognitive performance.

The catecholamine neurotransmitter precursor tyrosine increases anger during exposure to severe psychological stress.

RATIONALE: Acute stress produces behavioral and physiological changes modulated by central catecholamines (CA). Stress increases CA activity, and depletion of CA stores reduces responses to stress. Increasing CA activity by administration of the dietary amino acid CA precursor tyrosine may increase responsiveness to stress. This study determined whether tyrosine enhances the ability of humans to respond to severe stress. METHODS: Severe psychological stress was generated during training at Survival, Evasion, Resistance, and Escape (SERE) School. The acute stressor consisted of two mock interrogations conducted during several days of simulated captivity. Seventy-eight healthy male and female military personnel participated in this double-blind, between-subjects study, in which they received either tyrosine (300 mg/kg, N = 36) or placebo (N = 36). Tyrosine (or placebo) was administered in food bars in two doses of 150 mg/kg each approximately 60 min before each mock interrogation. Mood (Profile of Mood States), saliva cortisol, and heart rate (HR) were assessed prior to stress exposure during a week of academic training preceding mock captivity and immediately following the mock interrogations. RESULTS: The severe stress produced robust effects on mood (i.e., increased tension, depression, anger, fatigue, vigor, and confusion; p < .001), cortisol, and HR (p < .001). Tyrosine increased anger (p = .002, ANOVA treatment condition by test session interaction) during stress but had no other effects. CONCLUSION: Tyrosine did not alter most subjective or physiological responses to severe acute stress, but it increased ratings of anger. The modest increase in anger may be an adaptive emotional response in stressful environments.

Transient decrements in mood during energy deficit are independent of dietary protein-to-carbohydrate ratio.

Energy deficit and dietary macronutrient intake are thought to independently modulate cognition, mood and sleep. To what extent manipulating the dietary ratio of protein-to-carbohydrate affects mood, cognition and sleep during short-term energy deficit is undetermined. Using a randomized, block design, 39 non-obese young adults (21±1 years, BMI 25±1 kg/m(2)) consumed diets containing 0.8 g, 1.6 g or 2.4 g protein per kg body weight per day for 31 days. Carbohydrate intake was reduced to accommodate higher protein intakes while dietary fat was maintained at 30% of total energy intake. Cognitive performance, mood, self-reported sleep quality, and plasma amino acid concentrations were periodically assessed during a 10-day energy balance period and a subsequent 21-day, 40% energy deficit period. Anger, tension and total mood disturbance increased during the initial ten days of energy deficit (P<0.05), but by the end of the energy deficit returned to levels not different from those measured during energy balance. No effects of dietary protein-to-carbohydrate ratio on cognitive performance, mood or self-reported sleep quality were observed during energy balance or energy deficit. Thus, high-protein, low-carbohydrate, moderate-fat diets do not appear to benefit or impair cognition, mood or sleep in non-obese adults during energy deficit. These findings suggest that energy deficit may initially be psychologically difficult for non-obese individuals attempting to lose weight, but that these changes are transient. Employing strategies that alleviate decrements in mood during this initial period of adaptation may help sustain weight loss efforts.

The physiological and psychological effects of combat ration feeding during a 12-day training exercise in the tropics.

The health and psychological effects of combat ration pack (CRP) feeding during 12 days of military training in a tropical environment were investigated. Three groups of air defence guards (ADGs) received either: freshly prepared foods (fresh group, 15 mega joule (MJ), 3,600 kcal, N=13), full CRP (15 MJ, 3,600 kcal, N=10), or one-half CRP (7.5 MJ, 1,800 kcal, N=10). Underconsumption by the full CRP group resulted in CRP groups experiencing similar weight loss, protein catabolism, and immune suppression (both cell-mediated and humoral), whereas the fresh group maintained their weight and protein balance and cell-mediated immune status. CRP groups reported greater fatigue than the fresh group. All ADGs experienced poor sleep quality and declining folate and iron status. ADGs drank insufficient water to prevent dehydration. In the medium term, ADGs were able to adapt to restricted food consumption and poor sleep quality with no decrement in physical fitness or cognition.

Positive effects of basic training on cognitive performance and mood of adult females.

OBJECTIVE: This study investigated whether a stressful military training program, the 9- to 10-week U.S. Army basic combat training (BCT) course, alters the cognitive performance and mood of healthy young adult females. BACKGROUND: Structured training programs including adolescent boot camps, sports training camps, learning enrichment programs, and military basic training are accepted methods for improving academic and social functioning. However, limited research is available on the behavioral effects of structured training programs in regard to cognitive performance and mood. METHOD: Two separate, within-subject studies were conducted with different BCT classes; in total 212 female volunteers were assessed before and after BCT. In Study 1, Four-Choice Reaction Time, Match-to-Sample, and Grammatical Reasoning tests were administered. The Psychomotor Vigilance Test (PVT) was administered in Study 2. The Profile of Mood States (POMS) was administered in both studies. RESULTS: In Study 1, reaction time to correct responses on all three of the performance tests improved from pre- to post-BCT. In Study 2, PVT reaction time significantly improved. All POMS subscales improved over time in the second study, whereas POMS subscales in the first study failed to meet criteria for statistically significant differences over time. CONCLUSION: Cognition and mood substantially improved over military basic training. These changes may be a result of structured physical and mental training experienced during basic training or other factors not as yet identified. APPLICATION: Properly structured training may have extensive, beneficial effects on cognitive performance and mood; however, additional research is needed to determine what factors are responsible for such changes.

Efficacy of eat-on-move ration for sustaining physical activity, reaction time, and mood.

UNLABELLED: Repeated carbohydrate feedings and caffeine have been shown to increase self-paced physical activity. Whether a field ration pack that promotes snacking of these items would enhance physical activity remains unclear. PURPOSE: Evaluate the effectiveness of a ration pack consisting of eat-on-move items to promote snacking, as well as caffeine items, as a nutritional strategy to improve performance. METHODS: Twenty-eight wildland firefighters consumed both an eat-on-move ration (first strike ration (FSR): 13.2 MJ, 420 g CHO, 665 mg caffeine daily) and entrée-based ration (meals, ready-to-eat (MRE): 11.9 MJ, 373 g CHO, 100 mg caffeine daily) for 2 d separated by 1 d. Diet order was counterbalanced. Outcome measurements included self-paced physical activity determined by actimetry, reaction time, number of eating occasions using dietary recall, and dietary intake from food wrapper collection. RESULTS: Total eating episodes were higher with FSR compared with MRE (P = 0.013; mean +/- SD: 8.2 +/- 1.3 vs 7.6 +/- 1.1 episodes x 2 d(-1)), as were 2-d energy intake (22.0 +/- 2.4 vs 18.4 +/- 2.5 MJ; P < 0.01), carbohydrate intake (698 +/- 76 vs 546 +/- 82 mg; P < 0.01), self-reported caffeine intake (347 +/- 262 vs 55 +/- 65 mg; P < 0.01), and average end-shift salivary caffeine (1.6 +/- 1.9 vs 0.7 +/- 1.0 microg x mL(-1); P < 0.01). Total activity counts were higher (P = 0.046) when consuming FSR (507,833 +/- 129,130 counts per shift) compared with MRE (443,095 +/- 142,208 counts per shift). This was accomplished by spending a greater percentage of work shift with activity counts >1000 counts x min(-1) (21 +/- 8% vs 18 +/- 6%; P = 0.01) and less percent of work shift <50 counts x min(-1) (33 +/- 10% vs 38 +/- 10%; P = 0.01). CONCLUSIONS: Delivery of energy and caffeine in a manner that promotes snacking behavior is advantageous for increasing self-selected physical activity during arduous labor.

A double-blind, placebo-controlled test of 2 d of calorie deprivation: effects on cognition, activity, sleep, and interstitial glucose concentrations.

BACKGROUND: Anecdotal information and limited research suggest that short-term caloric deprivation adversely affects cognition. However, this issue has not been studied using double-blind, placebo-controlled procedures, because the formulation of a calorie-deficient feeding regimen identical to one with calories is impossible using ordinary foods. Therefore, test meals varying in caloric content, but indistinguishable in sensory characteristics, were formulated using hydrocolloid-based gels as the principal structural component. OBJECTIVE: The purpose of this study was to examine the effects of 2 d of near-total caloric deprivation on cognitive function, satiety, activity, sleep, and glucose concentrations in a controlled environment. DESIGN: A double-blind, placebo-controlled crossover study of caloric deprivation was conduced in a controlled environment for 48 h. Cognitive function in 27 healthy young subjects was assessed repeatedly with standardized tests of vigilance, reaction time, learning, memory, logical reasoning, mood, and satiety. Wrist-worn monitors were used to assess ambulatory vigilance, activity, and sleep. Interstitial glucose concentrations were assessed continuously with a minimally invasive monitor. RESULTS: When the subjects received the near calorie-free diets, mean calorie consumption totaled 1311 kJ (313 kcal) over the testing period. During the fully fed treatment sessions, the subjects consumed a mean of 9612 kJ/d (2294 kcal/d), which matched their individual, daily energy requirements. Satiety and interstitial glucose concentrations were lower during the calorie-deprived diet (P < 0.001) than during the fully fed diet. There were no detectable effects of calorie deprivation on any aspect of cognitive performance, ambulatory vigilance, activity, or sleep. The mood states assessed, including fatigue, were not affected by calorie deprivation. CONCLUSIONS: Cognitive performance, activity, sleep, and mood are not adversely affected in healthy humans by 2 d of calorie-deprivation when the subjects and investigators are unaware of the calorie content of the treatments.