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.

Short sleep duration is associated with a wide variety of medical conditions among United States military service members.

OBJECTIVES: This cross-sectional study investigated self-reported sleep duration and its association with a comprehensive range of clinically-diagnosed medical condition categories (CDMCs), as well as the relationship between short sleep duration (≤6 h) and demographic/lifestyle factors, among United States military service members (SMs). METHODS: A stratified random sample of SMs (n = 20,819) completed an online questionnaire on usual daily hours of sleep and demographic/lifestyle characteristics. CDMCs for a six-month period prior to questionnaire completion were obtained from a comprehensive military electronic medical surveillance system and grouped into 33 CDMCs covering both broad and specific medical conditions. Prevalence of CDMCs was compared among three sleep duration categories (≤4, 5-6 and ≥7 h). RESULTS: SMs reported a mean ± standard deviation of 6.3 ± 1.4 h of sleep per day. After adjustment for demographic/lifestyle characteristics, shorter sleep duration was associated with higher odds of a medical condition in 25 of 33 CDMCs, with most (n = 20) demonstrating a dose-response relationship. The five CDMCs with the largest differences between ≤4 vs ≥ 7 h sleep were: diseases of the nervous system (odds ratio [OR] = 2.9, 95% confidence interval [95%CI] = 2.4-3.4), mental/behavioral diseases (OR = 2.7, 95%CI = 2.3-3.2), diseases of the musculoskeletal system (OR = 1.9, 95%CI = 1.6-2.1), diseases of the circulatory system (OR = 1.7, 95%CI = 1.3-2.2), and diseases of the digestive system (OR = 1.6, 95%CI = 1.2-2.0). Six hours of sleep or less was independently associated with older age, less formal education, race, Hispanic ethnicity, higher body mass index, smoking, and military service branch. CONCLUSIONS: In this young, physically active population, reporting shorter sleep duration was associated with a higher risk of multiple CDMCs.

Sleep and Injuries in Military Personnel With Suggestions for Improving Sleep and Mitigating Effects of Sleep Loss.

Sleep professionals suggest adults should sleep at least seven hours per night and define good sleep quality as 1) sleep onset =15 minutes, 2) one or fewer awakenings per night, 3) awake after sleep onset =20 minutes, and 4) sleep efficiency (ratio of sleep time to time in bed) =85%. This paper focuses on associations between injuries and sleep quality/duration among military personnel and strategies to optimize sleep and mitigate effects of sleep loss. Investigations among military personnel generally used convenience samples who self-reported their injury and sleep quality/quantity. Despite these limitations, data suggest that lower sleep quality or duration is associated with higher risk of musculoskeletal injury (MSI). Possible mechanisms whereby poor sleep quality/duration may influence MSI include hormonal changes increasing muscle catabolism, increases in inflammatory processes affecting post-exercise muscle damage, and effects on new bone formation. Sleep can be optimized by a slightly cool sleeping environment, bedding that maintains a stable thermal microclimate around the body, not using media devices near bedtime or in the sleeping environment, minimizing noise, and having regular bed and awaking times. Sleep loss mitigation strategies include napping (<30 to 90 minutes), sleep banking (extended time in bed), and judicious use of caffeine or modafinil.

Dietary Supplement Use in US Army Personnel: A Mixed-Methods, Survey and Focus-Group Study Examining Decision Making and Factors Associated With Use.

BACKGROUND: Dietary supplement (DS) use by Army personnel is high and is a safety and readiness issue. OBJECTIVE: Our aim was to examine factors motivating use of DSs among US Army personnel and preferred safety education strategies. DESIGN: This mixed-method study used a validated DS questionnaire and subsequent focus groups that were formed based on questionnaire-identified demographic characteristics. An embedded qualitative dominant design was used. PARTICIPANTS/SETTING: Data were collected from April to July 2015 from active duty soldiers at 3 military installations in the United States. MAIN OUTCOME MEASURES: A self-report questionnaire (n = 289) provided data on demographic characteristics, health, exercise, detailed use, and attitudes regarding DS safety and efficacy. Fourteen focus-group sessions (n = 129) examined factors motivating DS use, education strategies, and identified themes and DS-related behaviors. STATISTICAL ANALYSIS PERFORMED: Descriptive statistics and χ2 analyses were conducted. RESULTS: Of the soldiers who completed questionnaires, 83% were male, 60% were enlisted, and 40% were officers; mean age ± standard deviation was 27.6 ± 0.36 years and 75% used at least 1 type of DS per week: 52% used protein/amino acids, 47% used multivitamins/minerals, and 35% used a combination of products. Focus groups indicated reasons for use included physical appearance, fitness, peer endorsement, ease of access, limited availability of healthy food, occupational demands, and health. Participants requested education from an expert on safe use that was not focused on dangerous products. CONCLUSIONS: Soldiers are high DS users, especially products marked for purported performance enhancement. Motivating factors for DS use are fitness/appearance and occupational demands, but soldiers lack knowledge of DS regulatory requirements and safety/efficacy. Soldiers wished to receive education on DSs from trusted health care professionals, such as registered dietitian nutritionists, that was not focused on dangerous products. Study findings suggest guidance and education should occur before periods of high DS use, such as deployment.

The effect of sleep restriction on cognitive performance in elite cognitive performers: a systematic review.

STUDY OBJECTIVES: To synthesize original articles exploring the effects of sleep restriction on cognitive performance specifically for Elite Cognitive Performers, i.e. those who engage in cognitively demanding tasks with critical or safety-critical outcomes in their occupation or area of expertise. METHODS: Backward snowballing techniques, gray literature searches, and traditional database searches (Embase, MEDLINE, Web of Science, Google Scholar, PSYCinfo, and SportDiscus) were used to obtain relevant articles. A quality assessment was performed, and the risk of training effects was considered. Results were narratively synthesized. Fourteen articles fit the criteria. Cognitive outcomes were divided into three categories defined by whether cognitive demands were "low-salience," "high-salience stable," or "high-salience flexible." RESULTS: Low-salience tests (i.e. psychomotor vigilance tasks & serial reaction tests), mainly requiring vigilance and rudimentary attentional capacities, were sensitive to sleep restriction, however, this did not necessarily translate to significant performance deficits on low-salience occupation-specific task performance. High-salience cognitive outcomes were typically unaffected unless when cognitive flexibility was required. CONCLUSIONS: Sleep restriction is of particular concern to occupations whereby individuals perform (1) simple, low-salience tasks or (2) high-salience tasks with demands on the flexible allocation of attention and working memory, with critical or safety-critical outcomes.

Caffeine, Energy Beverage Consumption, Fitness, and Sleep in U.S. Army Aviation Personnel.

BACKGROUND: Caffeine-containing products and dietary supplements are widely used by military populations, but little is known about their use by aviation personnel. This study assessed self-reported sleep, fitness, work-schedules, and caffeine/energy drink use.METHODS: A standardized survey was conducted in person by study personnel using tablet computers. A total of 188 aircrew members from the Combat Aviation Brigade at Fort Campbell, KY, participated in the survey. Focus groups were conducted with a subset of 47 subjects.RESULTS: The majority of subjects reported their physical fitness, health, and diets were good. They reported sleeping about 6 h per day and stated they needed additional sleep to feel fully rested. Their caffeine consumption averaged 346 ± 23 mg · d-1 with most derived from coffee (139 ± 12 mg · d-1) and energy drinks (110 ± 13 mg · d-1). About half (55%) of participants used energy drinks at least once per week and they consumed greater amounts of caffeine than nonusers. Focus group data indicated crewmembers primarily consumed energy drinks to enhance performance degraded by variations in work schedules and lack of sufficient sleep. Participants expressed a desire for additional education on diets and energy drinks as well as on aeromedical policies governing energy drink and supplement use.CONCLUSIONS: Caffeinated products, including coffee and energy drinks, are routinely used by Army aircrews to increase alertness. Aircrew personnel consider them generally safe, but would like to receive education about these beverages, other dietary issues, and Army policies governing their use in aircrew.Bukhari AS, Caldwell JA, DiChiara AJ, Merrill EP, Wright AO, Cole RE, Hatch-McChesney A, McGraw SM, Lieberman HR. Caffeine, energy beverage consumption, fitness, and sleep in U.S. Army aviation personnel. Aerosp Med Hum Perform. 2020; 91(8):641-650.

Demographics, sleep, and daily patterns of caffeine intake of shift workers in a nationally representative sample of the US adult population.

STUDY OBJECTIVE: Caffeine is the most widely consumed stimulant in the world, and sociodemographic factors including occupation are associated with intake. Shift work, required in various occupations, is associated with poor sleep, inadequate diet, and adverse health effects. Using a large nationally representative database, demographics, sleep, and caffeine intake of US adults working various shifts were assessed. METHODS: The 24-hour dietary recall data from NHANES 2005-2010 (N = 8,500) were used to estimate caffeine intake from foods and beverages. Work shifts were self-reported as follows: regular day shift; evening shift; night shift; rotating shift; or other shift. Regression analyses assessed associations of shift work with caffeine intake after adjustment for sociodemographic factors. RESULTS: Approximately 74% of employed adults were day-shift workers and 26% were nonday-shift workers. Night-shift workers slept for 6.25 ± 0.09 hours per day, somewhat less than day-shift workers who only slept 6.83 ± 0.02 hours (p < .0001). Mean 24-hour weekday caffeine intake of evening-, night-, and rotating-shift workers (217 ± 23, 184 ± 19, and 206 ± 15 mg, respectively) was similar (p > .3) to day-shift workers (203 ± 5 mg). Regardless of work schedule, individuals consumed the most caffeine during morning hours. Evening- and night-shift workers reported consuming 36%-46% less caffeine during their work hours and 72%-169% more during nonwork hours than day-shift workers (p < .01). CONCLUSIONS: Total daily caffeine intake of shift workers is similar to nonshift workers; most caffeine is consumed in the morning regardless of shift. Because shift workers consume less caffeine during regular work hours and more during nonwork hours than day workers, they may be using caffeine to, in part, optimize off-duty alertness.

Sleep Patterns and Alertness in an Elite Super Rugby Team During a Game Week.

Sleep is a vital component of preparation, performance and recovery for a Super Rugby game. The purpose of this study was to quantify sleep behaviours and alertness of professional rugby union players during training and a game. Thirty-six rugby union players from a Super Rugby team wore a wrist-activity device (Readiband™) to measure sleep for 3 days before, 3 days after and on the night of an evening game. Players were separated into those selected to play the game (n = 23) and those who were not (n = 13). Alertness was assessed for all training and game times using bio-mathematical modelling. Alertness measures ≤90% were considered to reflect impaired reaction time. Those selected to play in the game progressively increased sleep duration over the nights prior to the game (by 92 min p ≤ 0.05) by delaying wake time. Players went to bed later after the game (02:20 ± 114 min vs 22:57 ± 60 min; p ≤ 0.001) which resulted in decreased sleep duration on game night compared to pre-game nights (296 ± 179 min vs 459 ± 78 min; p ≤ 0.05). Four players did not achieve any sleep on game night. Sleep duration appeared to be truncated by early morning training sessions (before 08:00) on the second and third mornings after the game. Alertness was >90% for all training and game times for all players. In conclusion, in the days leading into a Super Rugby game, players delay morning time at wake and consequently increase sleep duration with post-game sleep reduced in some.

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.

Effects of testosterone supplementation on body composition and lower-body muscle function during severe exercise- and diet-induced energy deficit: A proof-of-concept, single centre, randomised, double-blind, controlled trial.

BACKGROUND: Severe energy deficits during military operations, produced by significant increases in exercise and limited dietary intake, result in conditions that degrade lean body mass and lower-body muscle function, which may be mediated by concomitant reductions in circulating testosterone. METHODS: We conducted a three-phase, proof-of-concept, single centre, randomised, double-blind, placebo-controlled trial (CinicalTrials.gov, NCT02734238) of non-obese men: 14-d run-in, free-living, eucaloric diet phase; 28-d live-in, 55% exercise- and diet-induced energy deficit phase with (200 mg testosterone enanthate per week, Testosterone, n = 24) or without (Placebo, n = 26) exogenous testosterone; and 14-d recovery, free-living, ad libitum diet phase. Body composition was the primary end point; secondary endpoints included lower-body muscle function and health-related biomarkers. FINDINGS: Following energy deficit, lean body mass increased in Testosterone and remained stable in Placebo, such that lean body mass significantly differed between groups [mean difference between groups (95% CI), 2.5 kg (3.3, 1.6); P < .0001]. Fat mass decreased similarly in both treatment groups [0.2 (-0.4, 0.7), P = 1]. Change in lean body mass was associated with change in total testosterone (r = 0.71, P < .0001). Supplemental testosterone had no effect on lower-body muscle function or health-related biomarkers. INTERPRETATION: Findings suggest that supplemental testosterone may increase lean body mass during short-term severe energy deficit in non-obese, young men, but it does not appear to attenuate lower-body functional decline. FUNDING: Collaborative Research to Optimize Warfighter Nutrition projects I and II, Joint Program Committee-5, funded by the US Department of Defence.

The association of insomnia and sleep apnea with deployment and combat exposure in the entire population of US army soldiers from 1997 to 2011: a retrospective cohort investigation.

Since 2001, the United States has been engaged in the longest and most expensive overseas conflict in its history. Sleep disorders, especially insomnia and obstructive sleep apnea (OSA), are common in service members and appear related to deployment and combat exposure, but this has not been systematically examined. Therefore, the incidence of clinically diagnosed insomnia and OSA from 1997 to 2011 in the entire population of US Army soldiers was determined and associations of these disorders with deployment and combat exposure examined. This observational retrospective cohort study linked medical, demographic, deployment, and combat casualty data from all active duty US Army soldiers serving from 1997 to 2011 (n = 1 357 150). The mediating effects of multiple known comorbid conditions were considered. From 2003 to 2011, there were extraordinary increases in incidence of insomnia (652%) and OSA (600%). Factors increasing insomnia risk were deployment (risk ratio [RR] [deployed/not deployed] = 2.06; 95% confidence interval [CI], 2.04-2.08) and combat exposure (RR [exposed/not exposed] = 1.20; 95% CI, 1.19-1.22). Risk of OSA was increased by deployment (RR [deployed/not deployed] = 2.14; 95% CI, 2.11-2.17), but not combat exposure (RR [exposed/not exposed] = 1.00; 95% CI, 0.98-1.02). These relationships remained after accounting for other factors in multivariable analyses. A number of comorbid medical conditions such as posttraumatic stress disorder and traumatic brain injury mediated a portion of the association between the sleep disorders and deployment. It is essential to determine underlying mechanisms responsible for these very large increases in insomnia and OSA and introduce effective preventive measures.

Fatigue and its management in the workplace.

Fatigue and workplace sleepiness are consequences of modern industrial society. Fatigue is a complex biological phenomenon that occurs as a function of time awake, time-of-day, workload, health, and off-duty lifestyle. Fatigue is a function of two major biological factors - the homeostatic drive for sleep and circadian rhythm of sleepiness. The greatest cause of fatigue is insufficient or disrupted sleep. Excessive sleepiness in the workplace and on highways is a serious safety hazard, and insufficient or disrupted sleep results in numerous accidents and adverse mental and physical health outcomes. Evidence-based strategies that promote better sleep and optimize work/rest schedules can mitigate the impact of fatigue and sleep loss. Proper nap and sleep scheduling, work breaks, modeling and monitoring tools, fatigue detection technologies, and pharmacological countermeasures can be implemented at home and/or in the workplace to reduce performance and safety hazards. Education about obtaining adequate sleep, the dangers of fatigue in terms of both health and cognitive consequences, and the availability of scientifically-proven sleep-enhancement and alertness-management strategies is essential.

Prevalence of sleep disorders and sleep problems in an elite super rugby union team.

The aim of this study was to determine the prevalence of sleep disorders in an elite rugby union team using in-laboratory polysomnography (PSG) and sleep questionnaires. Twenty-five elite rugby union players underwent a night of PSG during the "off-season" of the Super Rugby competition to assess their sleep. Of interest were measurements that detected the presence of obstructive sleep apnea (OSA; apnea-hypopnea index ≥5 events/hr) and the presence of moderate-severe periodic leg movements during sleep (PLMs; ≥15 events/hr). Players completed sleep-related questionnaires to assess daytime sleepiness, perception of insomnia, risk of OSA, and the presence of restless legs syndrome (RLS) and underwent basic anthropometric assessments including body mass index and neck circumference. OSA was present in 24% (n=6) of players and PLMs ≥15 events/hr in 12% (n=3). Questionnaire responses showed that all players had insomnia defined subthreshold insomnia and excessive daytime sleepiness, two players were identified as being at risk for OSA and none were classified as having RLS. In conclusion, sleep disorders and excessive sleepiness are common in elite rugby union players. A process to identify and manage sleep disorders should be considered by teams to optimise their physical recovery, athletic performance and to safeguard their health.

Caffeine use in a Super Rugby game and its relationship to post-game sleep.

OBJECTIVE: To examine the relationship between regular game-related caffeine consumption on sleep after an evening Super Rugby game. METHODS: Twenty elite rugby union players wore a wrist-activity monitor to measure sleep for three days before, three days after and on the night of an evening Super Rugby game (19:00-21:00). Players ingested caffeine as they would normally (i.e. before and sometimes during a game) and saliva samples were collected before (17:00) and after (21:30) the game for caffeine concentration. RESULTS: Compared to the nights leading up to the game, on the night of the game, players went to bed 3 h later (23:08 ± 66 min vs 02:11 ± 114 min; p < .001) and had 1:30 hh:mm less sleep (5:54 ± 2:59 vs 8:02 ± 1:24 hh:mm; p < .05) and four players did not sleep after the game. Post-game caffeine saliva concentrations were greater than pre-game levels in 17 players (Pre-game 0.40 µg/mL vs Post-game 2.77 µg/mL; p < .001). The increase in caffeine saliva concentrations was moderately associated with an increase in sleep latency (p < .05), a decrease in sleep efficiency (p < .05), and a trend for a decrease in sleep duration (p = .06) on game night. CONCLUSION: Caffeine consumption before a Super Rugby game markedly increases post-game saliva caffeine levels. This may contribute to the observed 3.5 h delay in time at sleep onset and the 1.5 h reduction in sleep duration on the night of the game. This study highlights the need for a strategic approach to the use of caffeine within a Super Rugby team considering the potential effect on post-game sleep.

A Survey Instrument to Assess Intake of Dietary Supplements, Related Products, and Caffeine in High-Use Populations.

Substantial data on the use of dietary supplements by the general adult population are available, but many population subgroups have not been extensively studied. Because military service members and young people consume large amounts of dietary supplements, including for enhancement of physical performance, weight control, and bodybuilding, which can be dangerous, we developed a comprehensive questionnaire to characterize patterns of supplement use in these and other populations. The questionnaire has been used to study >7000 military service members and 1000 college students. This supplement article presents a detailed description of the questionnaire, which contains comprehensive questions on demographic characteristics, exercise habits, attitudes with regard to dietary supplements, and amount of money spent on supplements. Intakes of specific dietary supplements and caffeine, frequency of use, and reasons for use are assessed. The questionnaire was designed for studying dietary supplement and caffeine intake patterns with the use of paper-and-pencil administration to military populations and was modified for use with college students and for computer and Web administration. It is available online at https://go.usa.gov/xn9FP and in the Supplemental File for this publication. It can be used to study other populations if minor modifications are made. The online version of the questionnairewill be updated periodically as newversions become available. In conclusion, a validated, detailed, noncopyrighted questionnaire designed to assess the use of dietary supplements, energy drinks (and related products), and caffeine is available for use in diverse populations. The format of the questionnaire is adaptable to computer administration and scoring, and it can be customized for specific subpopulations, locations, and product categories including updates that reflect changes in the availability of supplements or availability of new products.

Physiological and psychological effects of testosterone during severe energy deficit and recovery: A study protocol for a randomized, placebo-controlled trial for Optimizing Performance for Soldiers (OPS).

BACKGROUND: The physiological consequences of severe energy deficit include hypogonadism and the loss of fat-free mass. Prolonged energy deficit also impacts physical performance, mood, attentiveness, and decision-making capabilities. This study will determine whether maintaining a eugonadal state during severe, sustained energy deficit attenuates physiological decrements and maintains mental performance. This study will also assess the effects of normalizing testosterone levels during severe energy deficit and recovery on gut health and appetite regulation. METHODS: Fifty physically active men will participate in a 3-phase, randomized, placebo-controlled study. After completing a 14-d, energy-adequate, diet acclimation phase (protein: 1.6g∙kg-1∙d-1; fat: 30% total energy intake), participants will be randomized to undergo a 28-d, 55% energy deficit phase with (DEF+TEST: 200mg testosterone enanthate per week) or without (DEF) exogenous testosterone. Diet and physical activity will be rigorously controlled. Recovery from the energy deficit (ad libitum diet, no testosterone) will be assessed until body mass has been recovered within ±2.5% of initial body mass. Body composition, stable isotope methodologies, proteomics, muscle biopsies, whole-room calorimetry, molecular biology, activity/sleep monitoring, personality and cognitive function assessments, functional MRI, and comprehensive biochemistries will be used to assess physiological and psychological responses to energy restriction and recovery feeding while volunteers are in an expected hypogonadal versus eugonadal state. DISCUSSION: The Optimizing Performance for Soldiers (OPS) study aims to determine whether preventing hypogonadism will mitigate declines in physical and mental function that typically occur during prolonged energy deficit, and the efficacy of testosterone replacement on recovery from severe underfeeding. TRIAL REGISTRATION: NCT02734238.

The Effects of the Removal of Electronic Devices for 48 Hours on Sleep in Elite Judo Athletes.

This study examined the effects of evening use of electronic devices (i.e., smartphones, etc.) on sleep quality and next-day athletic and cognitive performance in elite judo athletes. Over 6 consecutive days and nights, 23 elite Australian judo athletes were monitored while attending a camp at the Australian Institute of Sport (AIS). In 14 athletes, all electronic devices were removed on days 3 and 4 (i.e., for 48 hours: the "device-restricted group"), whereas 9 were permitted to use their devices throughout the camp (the "control group"). All athletes wore an activity monitor (Readiband) continuously to provide measures of sleep quantity and quality. Other self-reported (diary) measures included time in bed, electronic device use, and rate of perceived exertion during training periods. Cognitive performance (Cogstate) and physical performance (single leg triple hop test) were also measured. When considering night 2 as a "baseline" for each group, removal of electronic devices on nights 3 and 4 (device-restricted group) resulted in no significant differences in any sleep-related measure between the groups. When comparing actigraphy-based measures of sleep to subjective measures, all athletes significantly overestimated sleep duration by 58 ± 85 minutes (p = 0.001) per night and underestimated time of sleep onset by 37 ± 72 minutes (p = 0.001) per night. No differences in physical or cognitive function were observed between the groups. CONCLUSION: This study has shown that the removal of electronic devices for a period of two nights (48 hours) during a judo camp does not affect sleep quality or quantity or influence athletic or cognitive performance.

Two Days of Calorie Deprivation Induced by Underfeeding and Aerobic Exercise Degrades Mood and Lowers Interstitial Glucose but Does Not Impair Cognitive Function in Young Adults.

BACKGROUND: In studies assessing the effects of acute undernutrition on cognitive function, volunteers are sedentary and findings are equivocal, even though glucose concentrations fall substantially. However, military personnel and endurance athletes often are underfed when physical demands, and consequently energy expenditure, are substantial. OBJECTIVE: The objective of this study was to determine whether 2 d of near-total calorie deprivation combined with aerobic exercise degraded cognitive performance and mood. METHODS: A double-blind, placebo-controlled, crossover design was used. Twenty-three volunteers [17 men (mean ± SD age: 20.5 ± 0.7 y) and 6 women (mean ± SD age: 23.3 ± 1.4 y); mean ± SD body mass index (in kg/m2): 25 ± 3] participated for 68 h, including a 51-h inpatient phase in a calorie-deprived or fully fed state during which behavioral testing was conducted and interstitial glucose was monitored continuously. Mood and cognitive performance, including psychomotor and visual vigilance, visual match-to-sample, repeated acquisition (motor learning), N-back (working memory), and grammatical reasoning, were repeatedly assessed. During each condition, individual daily energy intake and expenditure were controlled. During calorie deprivation, volunteers consumed 266 ± 61 kcal/d; during full feeding, they consumed 3935 ± 769 kcal/d. Participants engaged in identical exercise sessions for 4 h/d at 40-65% of peak volume of oxygen uptake attained. RESULTS: Calorie deprivation did not affect any aspect of cognitive performance, but produced robust effects on mood measured by the Profile of Mood States, including increased tension (P < 0.001), fatigue (P < 0.001), and total mood disturbance (from -0.80 ± 5.1 to 20.1 ± 6.1; P < 0.001), and decreased vigor (P = 0.002), as indicated by treatment × trial (time) effects on ANOVA. Interstitial glucose concentrations were lower during calorie deprivation than in the fully fed condition (P = 0.002, treatment × trial interaction) and declined to 61 mg/dL by the end of the treatment condition. CONCLUSION: In healthy young men and women, 2 d of severe calorie deprivation in combination with substantial aerobic exercise adversely affects multiple aspects of mood, but not cognition, in spite of substantial reductions in interstitial glucose concentrations. This trial was registered at clinicaltrials.gov as NCT01603550.

A review of caffeine's effects on cognitive, physical and occupational performance.

Caffeine is consumed by over 80% of U.S. adults. This review examines the effects caffeine has on cognitive and physical function, since most real-world activities require complex decision making, motor processing and movement. Caffeine exerts its effects by blocking adenosine receptors. Following low (∼40mg or ∼0.5mgkg-1) to moderate (∼300mg or 4mgkg-1) caffeine doses, alertness, vigilance, attention, reaction time and attention improve, but less consistent effects are observed on memory and higher-order executive function, such as judgment and decision making. Effects on physical performance on a vast array of physical performance metrics such as time-to-exhaustion, time-trial, muscle strength and endurance, and high-intensity sprints typical of team sports are evident following doses that exceed about 200mg (∼3mgkg-1). Many occupations, including military, first responders, transport workers and factory shift workers, require optimal physical and cognitive function to ensure success, workplace safety and productivity. In these circumstances, that may include restricted sleep, repeated administration of caffeine is an effective strategy to maintain physical and cognitive capabilities.

Screening for Sleep Apnea in Morbidly Obese Pilots.

BACKGROUND: Debate regarding the merits of screening pilots for sleep apnea has been stimulated by recently issued guidance from the Federal Aviation Administration. It has long been appreciated that sleep apnea results in poor quality sleep, and that poor quality sleep is associated with daytime fatigue and decrements in performance. However, the relationship between sleep apnea and poor performance, including risk for accidents is not as well understood. Good quality data are available for commercial truck drivers and have helped influence transportation policy, but there is a lack of pilot specific data. The purpose of this article is to review the basic epidemiology, pathophysiology, and treatment of sleep apnea, including major risk factors for apnea, such as body mass index (BMI), and to look at what is known about the impact of sleep apnea on performance in transportation related occupations. While pilot specific data may be lacking, good quality data for commercial truckers are available and can be used to formulate rational public policy with the goal of improving aviation safety. This article was reviewed by the Council of the Aerospace Medical Association and approved as a position paper of the Association.