Developmental changes in structural and functional properties of hippocampal AMPARs parallels the emergence of deliberative spatial navigation in juvenile rats.

The neural mechanisms that support the late postnatal development of spatial navigation are currently unknown. We investigated this in rats and found that an increase in the duration of AMPAR-mediated synaptic responses in the hippocampus was related to the emergence of spatial navigation. More specifically, spontaneous alternation rate, a behavioral indicator of hippocampal integrity, increased at the end of the third postnatal week in association with increases in AMPAR response duration at SC-CA1 synapses and synaptically driven postsynaptic discharge of CA1 pyramidal neurons. Pharmacological prolongation of glutamatergic synaptic transmission in juveniles increased the spontaneous alternation rate and CA1 postsynaptic discharge and reduced the threshold for the induction of activity-dependent synaptic plasticity at SC-CA1 synapses. A decrease in GluA1 and increases in GluA3 subunit and transmembrane AMPAR regulatory protein (TARP) expression at the end of the third postnatal week provide a molecular explanation for the increase in AMPAR response duration and reduced efficacy of AMPAR modulators with increasing age. A shift in the composition of AMPARs and increased association with AMPAR protein complex accessory proteins at the end of the third postnatal week likely "turns on" the hippocampus by increasing AMPAR response duration and postsynaptic excitability and reducing the threshold for activity-dependent synaptic potentiation.

Transcranial Doppler investigation of hemodynamic alterations associated with blunt cervical vascular injuries in trauma patients.

OBJECTIVES: Blunt cervical vascular injuries, often missed with current screening methods, have substantial morbidity and mortality, and there is a need for improved screening. Elucidation of cerebral hemodynamic alterations may facilitate serial bedside monitoring and improved management. Thus, the objective of this study was to define cerebral flow alterations associated with single blunt cervical vascular injuries using transcranial Doppler sonography and subsequent Doppler waveform analyses in a trauma population. METHODS: In this prospective pilot study, patients with suspected blunt cervical vascular injuries had diagnoses by computed tomographic angiography and were examined using transcranial Doppler sonography to define cerebral hemodynamics. Multiple vessel injuries were excluded for this analysis, as the focus was to identify hemodynamic alterations from isolated injuries. The inverse damping factor characterized altered extracranial flow patterns; middle cerebral artery flow velocities, the pulsatility index, and their asymmetries characterized altered intracranial flow patterns. RESULTS: Twenty-three trauma patients were evaluated: 4 with single internal carotid artery injuries, 5 with single vertebral artery injuries, and 14 without blunt cervical vascular injuries. All internal carotid artery injuries showed a reduced inverse damping factor in the internal carotid artery and dampened ipsilateral mean flow and peak systolic velocities in the middle cerebral artery. Vertebral artery injuries produced asymmetry of a similar magnitude in the middle cerebral artery mean flow velocity with end-diastolic velocity alterations. CONCLUSIONS: These data indicate that extracranial and intracranial hemodynamic alterations occur with internal carotid artery and vertebral artery blunt cervical vascular injuries and can be quantified in the acute injury phase by transcranial Doppler indices. Further study is required to elucidate cerebral flow changes resulting from a single blunt cervical vascular injury, which may guide future management to preserve cerebral perfusion after trauma.

Physical fitness and injury reporting among active duty and National Guard/Reserve women: associations with risk and lifestyle factors.

OBJECTIVE: As more women enter the military, it is important to understand how different risks and lifestyle factors influence physical fitness and injury among women in both active duty (AD) and National Guard/Reserve (NG/R). Women in military service are less fit and more likely to suffer musculoskeletal injuries during physical training than men. They also use more medical care during deployment than men. Using data from the Comprehensive Soldier and Family Fitness Global Assessment Tool 2.0 (GAT 2.0), self-reported health and lifestyle and behavioral risk factors were analyzed in nondeployed Army personnel, with the goals of examining (1) service-component differences across traditional risk and lifestyle factors, and (2) correlates of physical performance and physical activity-related injury. METHODS: Self-report GAT 2.0 data included health risk factors (overall perceived health, sleep, diet, tobacco and alcohol use), self-reported health metrics (height, weight, Army Physical Fitness Test (APFT) scores), and history of physical activity-related injury. The GAT 2.0 was completed by 1,322 AD and 1,033 NG/R women, and APFT data were available for a subsample of 605 AD and 582 NG/R women. RESULTS: Initial analyses of GAT 2.0 data indicated that AD had higher rates of fair/poor perceived health, poor sleep, and unhealthy diet compared to NG/R women. However, AD women had a lower APFT fail rate (8%) than NG (27%) and R (28%). Active duty women were more likely to experience a physical injury in the past 6 months (38%) than NG (19%) and R (22%) women, and more likely to seek medical care than NG/R women. Across all service components, predictive factors for APFT failure included high body mass index (BMI), fair/poor health, and unhealthy diet. Predictive factors for physical injury included high BMI, fair/poor health, and binge drinking. CONCLUSION: Our analyses suggest that AD women Soldiers are more physically fit than NG/R women Soldiers, which is accompanied by a greater prevalence of physical activity-related injuries. As women's roles expand into combat military occupation specialties, a thorough understanding of service component differences will be critical to inform training programs, mitigate physical injury, and enhance force health protection and readiness.

Women and exertional heat illness: identification of gender specific risk factors.

OBJECTIVE: With the expanding role of women into previously closed combat military occupational specialties, women will likely be exposed more to challenging and extreme conditions. Physical work or exercise in extreme environments could increase the risk for exertional heat illness (EHI) and exertional heat stroke (EHS), the most severe type of EHI. Although men have higher rates of EHS than women, women have slightly higher rates of other EHI. Women may respond differently to exertion in the heat than men, as they typically have higher percentage of body fat (BF%) and lower aerobic power. Further, published pilot-data using the Israeli heat tolerance test (HTT) indicate that women are more likely to be classified as heat intolerant than men. The objectives of the present study were to (1) compare male and female classification patterns of heat tolerance, and (2) identify EHI risk factors that might account for the relationship between heat tolerance classification and sex. METHODS: Fifty-five male and 20 female participants were recruited from military and university communities to participate in a standardized HTT. Subjects underwent measures to calculate anthropometric variables (BF%, body surface area, and waist circumference), a maximal oxygen uptake test to assess aerobic power (VO2max), and a standardized HTT, which consisted of treadmill walking at 5 km/h at a 2% grade for 120 minutes at 40°C and 40% relative humidity. Heat intolerance was defined as attaining a maximum heart rate (HR) greater than 150 bpm or a core body temperature (Tc) more than 38.5°C. Separate hierarchical regressions were conducted using categorical (heat tolerant/intolerant) and continuous (physiological strain index, maximum HR, Tc) HTT outcomes. Risk factors were identified with and without controlling for sex. RESULTS: Women were 3.7 (95% CI, 1.21-11.24) times more likely to be heat intolerant than men (χ²=6.85, P<.01). Compared to men, women had significantly higher BF% and lower body surface area, waist circumference, and VO2max. All heat intolerant participants had lower VO2max and higher BF% than those who were classified as heat tolerant. When VO2max and BF% were entered into regression equations to predict HTT outcomes, sex became nonsignificant; VO2max predicted maximum HR and physiological strain index after controlling for sex. CONCLUSION: The present study found that differences between men and women in heat tolerance classification are largely explained by VO2max. The higher rates of heat intolerance among women likely correlate with higher EHI risk, and underscore the need to understand the physiological and thermoregulatory differences between men and women. As lower aerobic power is a major risk factor for EHI, maximizing the aerobic power of women will be critical to force health protection and readiness as they integrate into combat military occupational specialties.

Nutrition as a component of the performance triad: how healthy eating behaviors contribute to soldier performance and military readiness.

OBJECTIVE: Nutrition is a critical element of Soldier health and performance. Food choices, meal timing, and dietary intake behaviors contribute to nutritional fitness. The objectives of this study were to describe Soldier dietary behaviors and quantify the association between healthy eating behaviors and demographic, lifestyle, and psychosocial factors. METHODS: The Comprehensive Soldier and Family Fitness Global Assessment Tool (GAT) assesses emotional, social, family, and spiritual fitness. In 2012, 57 pilot questions were added to the GAT to create a physical dimension that included nutrition assessments. Participants included 13,858 Active Duty, Reserve, and National Guard Soldiers: 83% male; 85% enlisted; a mean age of 28±9 years. A Healthy Eating Score (HES-5) was calculated from 5 questions assessing frequency of fruit, vegetable, whole grain, dairy, and fish intake (Cronbach α=0.81). Associations between HES-5 and other dietary habits, physical activity patterns, and GAT psychosocial dimension scores were examined. RESULTS: Soldiers who ate breakfast regularly (6 times/week or more), drank 7 servings or more of water/day, and met weekly exercise recommendations were more likely to be in the highest HES-5 quartile than those who did not. Those who passed their Army Physical Fitness Test (APFT) in the top quartile were also more likely to report high HES-5 scores than those who failed (P<.001). Soldiers with healthy anthropometric measures and the highest emotional, social, family, and spiritual fitness scores were also more likely to be in the top HES-5 quartile than those with unhealthy measures and with the lowest fitness scores (P<.001). CONCLUSION: The HES-5 may be a useful index for characterizing dietary intake behaviors. Healthy dietary intake behaviors are associated with all dimensions of health, physical fitness, and psychosocial status.

Sleep as a component of the performance triad: the importance of sleep in a military population.

OBJECTIVE: Sleep habits among military populations are problematic. Poor sleep hygiene occurs in parallel with the global increase in obesity and metabolic syndrome and contributes to a decrease in performance. The extent of sleep issues needs to be quantified to provide feedback for optimizing warfighter performance and readiness. This study assessed various health behaviors and habits of US Army Soldiers and their relationship with poor sleep quality by introducing a set of new questions into the Comprehensive Soldier and Family Fitness (CSF2) Global Assessment Tool (GAT). METHODS: Subjects included 14,148 US Army Active, Reserve, and National Guard members (83.4% male) who completed the GAT, a self-report questionnaire that measures 4 fitness dimensions: social, family, emotional, and spiritual. Approximately 60 new questions, including ones on sleep quality, within the fifth CSF2 dimension (physical) were also answered. A sleep score was calculated from 2 questions validated in the Pittsburgh Insomnia Rating Scale (0 to 6). RESULTS: Poor sleepers (5-6) were significantly (P<.001) more likely than good sleepers (0-1) to consider themselves in fair or poor health, be overweight or obese, and score in the lowest quartile of the emotional, social, family, and spiritual fitness dimensions. Additionally, poor sleepers were significantly (P<.001) less likely to have a healthy body mass index and waist circumference, eat breakfast 6 or more times a week, meet aerobic exercise and resistance training recommendations, and pass their Army Physical Fitness Test in the top quartile. CONCLUSION: This study examined sleep quality in a group of military personnel and indicated significant associations between quality of sleep and physical performance, nutritional habits, measures of obesity, lifestyle behaviors and measures of psychosocial status. Targeted educational interventions and resources are needed to improve sleep patterns based on behaviors that can be most easily modified.