Caffeine and energy drink use by combat arms soldiers in Afghanistan as a countermeasure for sleep loss and high operational demands.

OBJECTIVES: Combat deployments are characterized by high operational demands with limited opportunities for sleep leading to fatigue and degraded cognitive and operational performance. Caffeine in moderate doses is recognized as an effective intervention for physical and cognitive decrements associated with sleep loss. METHODS: This report is based on data collected by two separate, independently conducted surveys administered in Afghanistan in 2011-2012. It assessed caffeine use and sleep disruption among U.S. Army combat soldiers (J-MHAT 8; n = 518) and among deployed soldiers with different military assignments (USARIEM Deployment Survey; n = 260). RESULTS: Daily caffeine intake assessed in the J-MHAT 8 survey averaged 404 ± 18 mg. In the USARIEM Deployment Survey, intake was 303 ± 29 mg and was significantly higher among combat arms soldiers (483 ± 100 mg) compared to combat service support personnel (235 ± 23 mg). In both surveys, over 55% of total caffeine intake was from energy drinks. Additional sources of caffeine included coffee, tea, sodas, gum, candy, and over-the-counter medications. Higher caffeine intake was not associated with ability to fall asleep at night or wake-up in the morning (J-MHAT 8 survey). Higher caffeine consumption was associated with disrupted sleep from high operational tempo and nighttime duties of combat operations. DISCUSSION: Overall caffeine consumption and energy drink use in Afghanistan was greater than among non-deployed soldiers and civilians. Caffeine was frequently used as a countermeasure during night operations to offset adverse effects of sleep loss on physical and cognitive function, consistent with current Department of the Army recommendations.

Effects of Combat Deployment on Anthropometrics and Physiological Status of U.S. Army Special Operations Forces Soldiers.

INTRODUCTION: U.S. Army Special Operations Forces (SOF) soldiers deploy frequently and conduct military operations through special warfare and surgical strike capabilities. Tasks required to execute these capabilities may induce physical and mental stress and have the potential to degrade soldier physiological status. No investigations have longitudinally characterized whether combat deployment alters anthropometrics or biochemical markers of physiological status in a SOF population of frequent deployers. MATERIALS AND METHODS: Effects of modern combat deployment on longitudinal changes in anthropometrics and physiological status of elite U.S. Army SOF soldiers (n = 50) were assessed. Changes in measures of body composition, grip strength, physiological status, and health behaviors from baseline to postdeployment were determined with paired t test and McNemar's statistic. Baseline measures were obtained between 4 and 8 weeks before deployment. Deployment length was a uniform duration of time between 3 and 6 months (all soldiers completed the same length of deployment). Post hoc analyses determined change in body mass within quartiles of baseline body mass with paired t test and associations between change in sex hormone-binding globulin (SHBG) and change in body mass with correlation coefficient. The study was approved by the Human Use Review Committee at the U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts. RESULTS: In response to deployment, increases in lean mass (77.1 ± 7.6 to 77.8 ± 7.5 kg), maximum grip strength (57.9 ± 7.2 to 61.6 ± 8.8 kg), and conduct of aerobic (156 ± 106 to 250 ± 182 minutes/week) and strength training (190 ± 101 to 336 ± 251 minutes/week) exercise were observed (p < 0.05). Increases in serum SHBG (35.42 ± 10.68 to 38.77 ± 12.26 nmol/L) and decreases in serum cortisol (443.2 ± 79.3 to 381.9 ± 111.6 nmol/L) were also observed (p < 0.05). Body mass changes were dependent on baseline body mass. Soldiers in the lowest quartile of baseline body mass increased body mass (75.6 ± 2.6 vs. 76.6 ± 2.8 kg, p = 0.03), as did those in the second quartile (81.6 ± 2.0 vs. 83.7 ± 3.5 kg, p = 0.02). Those in the third quartile also tended to increase body mass (89.2 ± 2.6 vs. 90.9 ± 3.3 kg, p = 0.05), while those in the upper quartile tended to decrease body mass (98.5 ± 3.6 vs. 96.7 kg, p = 0.06). Change in SHBG was inversely correlated with change in body mass (r = -0.33, p = 0.02). There were no changes in fat mass, body fat percentage, waist circumference, neck circumference, total testosterone, calculated bioavailable or free testosterone, high-sensitivity C-reactive protein, tumor necrosis factor-α, interleukin-1ß, or interleukin-6. Inflammatory markers were skewed toward lower values. CONCLUSIONS: Overall, physiological status of elite SOF soldiers characterized by multiple prior deployments was minimally impacted by combat deployment, in the absence of major unit casualties. The majority experienced some adaptive changes, including increased lean mass, grip strength, time spent engaged in exercise, and decreased levels of the stress hormone cortisol. Mechanisms contributing to inverse correlations between change in SHBG and change in body mass may be further clarified. Future investigations may also more fully characterize the degradation and optimization of health and physiological status of SOF training and deployment cycles with in-theater data collection and repeated measures.

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.

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.

Improved Mood State and Absence of Sex Differences in Response to the Stress of Army Basic Combat Training.

BACKGROUND: It is reported that women are more susceptible to stress than men but they have not been compared in stressful, real-world, team-centered, occupational/training environments. This study investigated effects of Army Basic Combat Training (BCT), a structured military training program, on the mood of young adult men and women. METHODS: Using the Profile of Mood States (POMS) questionnaire, 169 soldiers (98 men and 71 women) were assessed prior to starting BCT and after each phase of training. RESULTS: Significant improvements were found in five of six subscales over the course of BCT. Men and women responded positively and similarly to BCT. POMS scores attributable to an interaction of time and each factor of sex, age group, education level, ethnicity, and race were not significantly different. CONCLUSIONS: When studied in the same environment and exposed to the same stressors, men and women in this study responded similarly. The positive changes in mood in both sexes during BCT appear to result from the interaction of a structured physical and cognitive training program conducted in a team-oriented environment, and indicate that BCT enhances soldier mood similarly regardless of sex.

Effects of basic combat training on iron status in male and female soldiers: a comparative study.

OBJECTIVE: Iron is an essential micronutrient known to affect physical and cognitive performance. Studies indicate a significant reduction in iron status in female Soldiers immediately following military training, although the comparative effects of military training on iron status between male and female Soldiers have not been examined. The objective of this study was to compare the longitudinal effects of US Army basic combat training (BCT) on iron status indicators in a group of male and female Soldiers. METHODS: A total of 154 male and female Soldiers (89 and 65, respectively) completed the study. Blood was collected at 4 time-points during BCT (weeks 0, 3, 6, 9) and dietary iron intake was assessed at weeks 0 and 9. Iron status indicators included hemoglobin, serum ferritin (SF), soluble transferrin receptor (sTfR), and transferrin saturation (TS). RESULTS: Iron status was greater in male Soldiers than female Soldiers, as hemoglobin and SF levels were higher (P<.05) and sTfR levels were lower (P<.05) in males as compared to females at each time-point. Despite a mean increase of greater than 25% in iron intake (mg/day) among both male (15±13 to 20.2±14.4) and female Soldiers (12.8±9.7 to 16±6.2) over the course of BCT, iron status declined in both groups. As compared to baseline, SF declined (P<.05) by 21% and 47%, sTfR increased (P<.05) by 17% and 30%, and TS declined (P<.05) by 23% and 54% in male and female Soldiers, respectively, over the course of BCT. CONCLUSIONS: These data indicate that although dietary iron intake improves, iron status declines in both male and female Soldiers during BCT, and the decline in female Soldiers is of a greater magnitude. Future studies should aim to determine the mechanism by which iron status declines during military training, with a focus on functional outcomes affecting Soldier health and performance.

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.

Differential effects of military training on fat-free mass and plasma amino acid adaptations in men and women.

Fat-free mass (FFM) adaptations to physical training may differ between sexes based on disparities in fitness level, dietary intake, and levels of plasma amino acids (AA). This investigation aimed to determine FFM and plasma AA responses to military training, examine whether adaptations differ between male and female recruits, and explore potential associations between FFM and AA responses to training. Body composition and plasma AA levels were assessed in US Army recruits (n = 209, 118 males, 91 females) before (baseline) and every three weeks during basic combat training (BCT), a 10-week military training course. Body weight decreased in men but remained stable in women during BCT (sex-by-time interaction, P < 0.05). Fifty-eight percent of recruits gained FFM during BCT, with more (P < 0.05) females (88%) gaining FFM than males (36%). Total plasma AA increased (P < 0.05) during BCT, with greater (P < 0.05) increases observed in females (17%) then in males (4%). Essential amino acids (EAA) and branched-chain amino acids (BCAA) were increased (P < 0.05) in females but did not change in males (sex-by-time interaction, P < 0.05). Independent of sex, changes in EAA (r = 0.34) and BCAA (r = 0.27) from baseline were associated with changes in FFM (P < 0.05); greater (P < 0.05) increases in AA concentrations were observed for those who gained FFM. Increases in FFM and plasma AA suggest that BCT elicits a more pronounced anabolic response in women compared to men, which may reflect sex-specific differences in the relative intensity of the combined training and physiological stimulus associated with BCT.

Vitamin D status, dietary intake, and bone turnover in female Soldiers during military training: a longitudinal study.

BACKGROUND: Vitamin D is an essential nutrient for maintaining bone health, to include protecting against stress fracture during periods of rapid bone turnover. The objective of this longitudinal, observational study was to assess vitamin D status, biomarkers of bone turnover, and vitamin D and calcium intake in female Soldiers (n = 91) during US Army basic combat training (BCT). METHODS: Anthropometric, biological and dietary intake data were collected at wk 0, 3, 6, and 9 of the 10 wk BCT course. Mixed models repeated measures ANOVAs were used to assess main effects of time, race, and time-by-race interactions. RESULTS: White volunteers experienced a decrease in serum 25(OH)D levels, whereas non-white volunteers experienced an increase during BCT. However, serum 25(OH)D levels were lower in non-whites than whites at all timepoints (P-interaction < 0.05). Group mean PTH levels increased (P < 0.05) during the first 3 wk of training, remained elevated for the duration of BCT, and were higher in non-whites compared to whites (P-race < 0.05). Biomarkers of both bone formation (bone alkaline phosphatase and procollagen I N-terminal peptide) and resorption (tartrate-resistant acid phosphatase and C-terminal telopeptide) increased (P < 0.05) during BCT, indicating increased bone turnover. Estimated daily intakes of vitamin D and calcium were below recommended levels (15 µg and 1000 mg/day, respectively), both before (group mean ± SEM; 3.9 µg/d ± 0.4 and 887 mg/d ± 67) and during BCT (4.1 µg/d ± 0.3 and 882 mg/d ± 51). CONCLUSIONS: These findings demonstrate that female Soldiers experience dynamic changes in vitamin D status coupled with increased bone turnover and potentially inadequate vitamin D and calcium intake during military training.

Cardiometabolic risk in US Army recruits and the effects of basic combat training.

BACKGROUND: Cardiometabolic disease risk in US military recruits and the effects of military training have not been determined. This study examined lifestyle factors and biomarkers associated with cardiometabolic risk in US Army recruits (209; 118 male, 91 female, 23 ± 5 yr) before, during, and after basic combat training (BCT). METHODOLOGY/PRINCIPAL FINDINGS: Anthropometrics; fasting total (TC), high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol; triglycerides (TG); glucose; and insulin were measured at baseline and every 3 wks during the 10 wk BCT course. At baseline, 14% of recruits were obese (BMI>30 kg/m(2)), 27% were cigarette smokers, 37% were sedentary, and 34% reported a family history of cardiometabolic disease. TC was above recommended levels in 8%, LDL in 39%, TG in 5%, and glucose in 8% of recruits, and HDL was below recommended levels in 33% of recruits at baseline. By week 9, TC decreased 8%, LDL 10%, TG 13%, glucose 6% and homeostasis model assessment of insulin resistance (HOMA-IR) 40% in men (P<0.05). In women, TC, LDL, glucose and HOMA-IR were decreased from baseline at weeks 3 and 6 (P<0.05), but were not different from baseline levels at week 9. During BCT, body weight declined in men but not women, while body fat percentage declined in both men and women (P<0.05). CONCLUSIONS/SIGNIFICANCE: At the start of military service, the prevalence of cardiometabolic risk in US military recruits is comparable to that reported in similar, college-aged populations. Military training appears to be an effective strategy that may mitigate risk in young people through improvements in lipid profiles and glycemic control.

Risk factors for medical discharge from United States Army Basic Combat Training.

Past studies indicated that overall Basic Combat Training (BCT) attrition (discharge) was associated with various risk factors. BCT has changed considerably since many of these studies were conducted. This study examined Soldiers medically attrited from BCT. Potential attrition risk factor data on recruits (n = 4,005) were collected from medical records, BCT unit records, and questionnaires. Attrition data from Fort Jackson, South Carolina, showed 203 medical discharges. Cox regression (univariate and multivariate) obtained hazard ratios and 95% confidence intervals for attrition risk factors. Higher attrition risk was associated with female gender. Higher attrition risk for men was associated with cigarette smoking, injury during BCT, and less exercise before BCT. Higher attrition risk for both genders was associated with failure on the initial 2-mile run test and separated or divorced marital status. Attrition risk factors found in this study were similar to those previously identified despite changes in BCT.

Vitamin D status in female military personnel during combat training.

Vitamin D is an essential nutrient for maintaining bone health. Recent data suggest that vitamin D and calcium supplementation might affect stress fracture incidence in military personnel. Although stress fracture is a health risk for military personnel during training, no study has investigated changes in vitamin D status in Soldiers during United States (US) Army basic combat training (BCT). This longitudinal study aimed to determine the effects of BCT on 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) levels in female Soldiers. Serum 25(OH)D and PTH were assessed in 74 fasted Soldier volunteers before and after an 8-week BCT course conducted between August and October in Columbia, South Carolina. In the total study population, 25(OH)D levels decreased (mean ± SD) from 72.9 ± 30.0 to 63.3 ± 19.8 nmol/L (P < 0.05) and PTH levels increased from 36.2 ± 15.8 to 47.5 ± 21.2 pg/mL (P < 0.05) during BCT. Ethnicity affected changes in vitamin D status (ethnicity-by-time interaction, P < 0.05); 25(OH)D decreased (P < 0.05) in both Hispanic and non-Hispanic whites, but did not change in non-Hispanic blacks. Ethnicity did not affect BCT-induced changes in PTH. These data indicate that vitamin D status in female Soldiers may decline during military training in the late summer and early autumn months in the Southeastern US. Future studies should strive to determine the impact of military clothing and seasonality on vitamin D status, as well as the functional impact of declining vitamin D status on bone health.

Randomized, double-blind, placebo-controlled trial of an iron-fortified food product in female soldiers during military training: relations between iron status, serum hepcidin, and inflammation.

BACKGROUND: Iron status degrades in female soldiers during military training. Inflammation-mediated up-regulation of hepcidin, a key mediator of iron homeostasis, may be a contributing factor. OBJECTIVE: We measured the efficacy of an iron-fortified food product for maintaining iron status in female soldiers during basic combat training (BCT) and examined relations between iron status, serum hepcidin concentrations, and inflammation. DESIGN: A randomized, double-blind, placebo-controlled trial was conducted. Volunteers received an iron-fortified food product (total dose = 56 mg Fe/d) or a placebo twice daily during the 9-wk BCT course. Iron-status indicators, serum hepcidin concentrations, and markers of inflammation were measured pre- and post-BCT. RESULTS: BCT affected iron status; serum ferritin concentrations decreased (P < or = 0.05), and concentrations of soluble transferrin receptor (sTfR) and hemoglobin and the red cell distribution width increased (P < or = 0.05). Consumption of the iron-fortified food product attenuated declines in iron status in iron-deficient anemic soldiers; a group-by-time interaction was observed for hemoglobin and sTfR concentrations (P < or = 0.05). Serum hepcidin concentrations were not affected by BCT; however, hepcidin concentrations were lower in iron-deficient anemic soldiers than in those with normal iron status (P < or = 0.05) and were positively associated with serum ferritin (P < or = 0.05) and C-reactive protein (P < or = 0.05) concentrations pre- and post-BCT. CONCLUSIONS: Twice-daily consumption of an iron-fortified food product improved iron status in iron-deficient anemic soldiers but not in iron-normal or iron-deficient nonanemic soldiers. Serum hepcidin concentrations were not affected by training but were associated with iron status and inflammation pre- and post-BCT. This trial was registered at clinicaltrials.gov as NCT01100905.

Poor iron status is not associated with overweight or overfat in non-obese pre-menopausal women.

BACKGROUND: Associations between obesity and poor iron status have been described in children and adults. Proposed mechanisms for this association implicate a physiologic etiology, suggesting body fat accretion may progressively degrade iron status. However, the relationship between iron status and body composition in non-obese adults remains unclear. OBJECTIVE: In this study we examined the relationship between body composition, inflammation, and iron status in healthy, non-obese, pre-menopausal females. METHODS: Iron status was assessed using red cell distribution width, transferrin saturation, serum ferritin, and soluble transferrin receptor (sTfR). Tumor-necrosis factor-alpha provided a marker of inflammation, and body fat percentage (BF) was calculated from mean skinfold thickness measurements at 3 sites. RESULTS: In this cohort (n = 207), the prevalence of iron deficiency was similar (p > 0.05) between normal and overweight (BMI 25.0-30.0 kg/m(2)), and normal and overfat (BF >or=30.0%) volunteers. There were no differences in individual iron status indicators, including sTfR, between overweight or overfat volunteers as compared to normal weight and normal fat peers. Logistic regression analyses indicated that overfat volunteers had a lower (p < 0.05) risk of iron deficiency, whereas overweight individuals demonstrated no change in relative risk as compared to peers. CONCLUSION: These findings suggest that, in non-obese adults, decrements in iron status are not associated with increasing adiposity.

Randomized, double-blind, placebo-controlled trial of iron supplementation in female soldiers during military training: effects on iron status, physical performance, and mood.

BACKGROUND: Decrements in iron status have been reported in female soldiers during military training. Diminished iron status adversely affects physical and cognitive performance. OBJECTIVE: We wanted to determine whether iron supplementation could prevent decrements in iron status and improve measures of physical performance and cognitive status in female soldiers during basic combat training (BCT). DESIGN: In this 8-wk randomized, double-blind, placebo-controlled trial, soldier volunteers (n = 219) were provided with capsules containing either 100 mg ferrous sulfate or a placebo. Iron status indicator assays were performed pre- and post-BCT. Two-mile running time was assessed post-BCT; mood was assessed by using the Profile of Mood States questionnaire pre- and post-BCT. RESULTS: The BCT course affected iron status: red blood cell distribution width and soluble transferrin receptor were elevated (P < 0.05), and serum ferritin was lowered (P < 0.05) post-BCT. Iron supplementation attenuated the decrement in iron status; group-by-time interactions (P < 0.01) were observed for serum ferritin and soluble transferrin receptor. Iron supplementation resulted in improved (P < 0.05) vigor scores on the Profile of Mood States post-BCT and in faster running time (P < 0.05) in volunteers reporting to BCT with iron deficiency anemia. CONCLUSIONS: Iron status is affected by BCT, and iron supplementation attenuates the decrement in indicators of iron status in female soldiers. Furthermore, iron supplementation may prove to be beneficial for mood and physical performance during the training period. Future efforts should identify and treat female soldiers or athletes who begin training regimens with iron deficiency or iron deficiency anemia.

Injury reduction effectiveness of selecting running shoes based on plantar shape.

Popular running magazines and running shoe companies suggest that imprints of the bottom of the feet (plantar shape) can be used as an indication of the height of the medial longitudinal foot arch and that this can be used to select individually appropriate types of running shoes. This study examined whether or not this selection technique influenced injury risk during United States Army Basic Combat Training (BCT). After foot examinations, BCT recruits in an experimental group (E: n = 1,079 men and 451 women) selected motion control, stability, or cushioned shoes for plantar shapes judged to represent low, medium, or high foot arches, respectively. A control group (C: n = 1,068 men and 464 women) received a stability shoe regardless of plantar shape. Injuries during BCT were determined from outpatient medical records. Other previously known injury risk factors (e.g., age, fitness, and smoking) were obtained from a questionnaire and existing databases. Multivariate Cox regression controlling for other injury risk factors showed little difference in injury risk between the E and C groups among men (risk ratio (E/C) = 1.01; 95% confidence interval = 0.88-1.16; p = 0.87) or women (risk ratio (E/C) = 1.07; 95% confidence interval = 0.91-1.25; p = 0.44). In practical application, this prospective study demonstrated that selecting shoes based on plantar shape had little influence on injury risk in BCT. Thus, if the goal is injury prevention, this selection technique is not necessary in BCT.

Longitudinal decrements in iron status during military training in female soldiers.

Fe is an essential micronutrient required for optimal cognitive and physical performance. Cross-sectional studies indicate that training degrades Fe status in female military personnel; however, longitudinal studies to measure the direct impact of military training on Fe status and performance have not been conducted. As such, the objective of the present study was to determine the longitudinal effects of military training on Fe status in female soldiers. Fe status was assessed in ninety-four female soldiers immediately before and following a 9-week basic combat training (BCT) course. Fe status indicators included Hb, erythrocyte distribution width (RDW), serum ferritin, transferrin saturation and soluble transferrin receptor (sTfR). A 2-mile (3.2 km) run test was performed at the end of BCT to assess aerobic performance. Fe status was affected by BCT, as all Fe status indicators, excluding Hb, were diminished (P < or = 0.01) at the end of BCT. Fe status indicators at the end of BCT (Hb and RDW) were associated (P < or = 0.05) with running performance, as was the change in sTfR over the training period (r 0.320; P < or = 0.05). In conclusion, Fe status in female soldiers is degraded during BCT, and degraded Fe status is associated with diminished aerobic performance. Female athletes and military personnel should strive to maintain Fe status to optimise physical performance.