Search

PURPOSE: Initial military training (IMT) is a transitionary period wherein immune function may be suppressed and infection risk heightened due to physical and psychological stress, communal living, and sleep deprivation. This study characterized changes in biomarkers of innate and adaptive immune function, and potential modulators of those changes, in military recruits during IMT. METHODS: Peripheral leukocyte distribution and mitogen-stimulated cytokine profiles were measured in fasted blood samples, Epstein–Barr (EBV), varicella zoster (VZV), and herpes simplex 1 (HSV1) DNA was measured in saliva by quantitative polymerase chain reaction as an indicator of latent herpesvirus reactivation, and diet quality was determined using the healthy eating index measured by food frequency questionnaire in 61 US Army recruits (97% male) at the beginning (PRE) and end (POST) of 22-wk IMT. RESULTS: Lymphocytes and terminally differentiated cluster of differentiation (CD)4+ and CD8+ T cells increased PRE to POST, whereas granulocytes, monocytes, effector memory CD4+ and CD8+ T cells, and central memory CD8+ T cells decreased (P ≤ 0.02). Cytokine responses to anti-CD3/CD28 stimulation were higher POST compared with PRE, whereas cytokine responses to lipopolysaccharide stimulation were generally blunted (P < 0.05). Prevalence of EBV reactivation was higher at POST (P = 0.04), but neither VZV nor HSV1 reactivation was observed. Diet quality improvements were correlated with CD8+ cell maturation and blunted proinflammatory cytokine responses to anti-CD3/CD28 stimulation. CONCLUSIONS: Lymphocytosis, maturation of T-cell subsets, and increased T-cell reactivity were evident POST compared with PRE IMT. Although EBV reactivation was more prevalent at POST, no evidence of VZV or HSV1 reactivation, which are more common during severe stress, was observed. Findings suggest increases in the incidence of EBV reactivation were likely appropriately controlled by recruits and immune-competence was not compromised at the end of IMT.

This paper describes a Cold Weather Ensemble Decision Aid (CoWEDA) that provides guidance for cold weather injury prevention, mission planning, and clothing selection. CoWEDA incorporates current science from the disciplines of physiology, meteorology, clothing, and computer modeling. The thermal performance of a cold weather ensemble is defined by endurance times, which are the time intervals from initial exposure until the safety limits are reached. These safety limits correspond to conservative temperature thresholds that provide a warning of the approaching onset of frostbite and/or hypothermia. A validated six-cylinder thermoregulatory model is used to predict human thermal responses to cold while wearing different ensembles. The performance metrics, model, and a database of clothing properties were integrated into a user-friendly software application. CoWEDA is the first tool that allows users to build their own ensembles from the clothing menu (i.e., jackets, footwear, and accessories) for each body region (i.e., head, torso, lower body, hands, feet) and view their selections in the context of physiological strain and the operational consequences. Comparison of predicted values to skin and core temperatures, measured during 17 cold exposures ranging from 0 to −40°C, indicated that the accuracy of CoWEDA prediction is acceptable, and most predictions are within measured mean ± SD. CoWEDA predicts the risk of frostbite and hypothermia and ensures that a selected clothing ensemble is appropriate for expected weather conditions and activities. CoWEDA represents a significant enhancement of required clothing insulation (IREQ, ISO 11079) and wind chill index-based guidance for cold weather safety and survival.

INTRODUCTION Military load carriage can cause extreme energy expenditure (EE) that is difficult to estimate due to complex terrain grades and surfaces. Global Positioning System (GPS) devices capture rapid changes in walking speed and terrain but the delayed respiratory response to movement is problematic. We investigated the accuracy using GPS data in three different equations to estimate EE during complex terrain load carriage. METHODS Twelve active duty military personnel (age, 20 ± 3 yr; height, 174 ± 8 cm; body mass, 85 ± 13 kg) hiked a complex terrain trail on multiple visits under different external load conditions. Energy expenditure was estimated by inputting GPS data into three different equations: the Pandolf-Santee equation, a recent GPS-based equation from de Mullenheim et al.; and the Minimum Mechanics model. Minute-by-minute EE estimates were exponentially smoothed using smoothing factors between 0.05 and 0.95 and compared with mobile metabolic sensor EE measurements. RESULTS The Pandolf-Santee equation had no significant estimation bias (-2 ± 12 W; P = 0.89). Significant biases were detected for the de Mullenheim equation (38 ± 13 W; P = 0.004) and the Minimum Mechanics model (-101 ± 7 W; P < 0.001). CONCLUSIONS Energy expenditure can be accurately estimated from GPS data using the Pandolf-Santee equation. Applying a basic exponential smoothing factor of 0.5 to GPS data enables more precise tracking of EE during non-steady-state exercise.

Military working dogs (MWDs) operate under a wide range of conditions, including hot environments. Predicting how long a MWD can safely work without overheating is important for both health and performance. A Canine Thermal Model (CTM) was developed to predict core temperature (Tc) of MWDs. The CTM calculates heat storage from the balance of heat production from metabolism and heat exchange with the environment. Inputs to the CTM are: meteorological conditions (ambient temperature, relative humidity, solar radiation and wind speed), physical characteristics of the dog (mass, length), and metabolic activity (MET level, estimated from accelerometer data). The CTM was validated against Tc measured in 23 MWDs during training sessions (11.6 ± 5.0 min (mean ± standard deviation), range 4–26 min) in October (24 °C, 52% RH), March (14 °C, 74% RH), or August (28 °C, 64% RH), and 24 kennel MWDs during a standard exercise walk (11.4 ± 3.3 min, range 5.6–18 min) in July (26 °C, 77% RH). The CTM was considered acceptable if predicted Tc was within ±0.5 °C of measured Tc at the end of exercise. Compared to Tc at the end of training sessions (39.8 ± 0.6 °C, range 38.4–41.1 °C) and exercise walks (40.0 ± 0.7 °C, range 38.9–41.4 °C), the CTM-predicted Tc was within ±0.5 °C for 71 of 84 cases (85%) and 19 of 24 cases (79%), respectively. The mean difference between CTM-predicted and measured final Tc during training was -0.04 ± 0.43 °C, with 80 of 84 cases (95%) within the range of ±2 SD (Bland Altman comparison). During exercise walks the mean difference was -0.15 °C ± 0.57, with 23 of 24 cases (96%) within ±2 SD. These results support the use of the CTM to predict Tc of MWDs for the types of physical activities described above.

AB The location of the wet bulb globe temperature (WBGT) index measurement may affect heat stress flag category classification. Purpose: This study aimed to compare WBGT measurements at three locations along the Boston Marathon race course and compare WBGT estimates for meteorological stations and 72-h advanced WBGT forecasts. Methods: WBGT was measured hourly from 1000 to 1400 h at approximately 7 km, approximately 18 km, and approximately 30 km on the Boston Marathon race course. Simultaneous WBGT estimates were made for two meteorological stations southeast of the course via a commercial online system, which also provided 72-h advanced forecasts. Results: The measurement difference (mean +/- SD) among course locations was 0.2[degrees]C +/- 1.8[degrees]C WBGT (ANOVA, P > 0.05). The difference between course and stations was 1.9[degrees]C +/- 2.4[degrees]C WBGT (t-test, P 3[degrees]C WBGT (>0.5 flag category) in 111 of 245 paired comparisons (45%). Higher black globe and lower wet bulb temperatures explained over- and underestimates, respectively. Significant underestimates of WBGT resulted in misclassification of green (labeled white) and black (labeled red) course flag categories ([chi]2, P < 0.05). Forecast data significantly underestimated red (labeled amber) and black (labeled red) course flag categories. Conclusions: Differences in WBGT index along 23 km of the Boston Marathon race route can be small enough to warrant single measurements. However, significant misclassification of flag categories occurred using WBGT estimates for meteorological stations; thus, local measurements are preferred. If the relation between station WBGT forecasts and the race sites can be established, the forecast WBGT values could be corrected to give advanced warning of approximate flag conditions. Similar work is proposed for other venues to improve heat stress monitoring.

Heat strain is common in military working dogs (MWDs), but can be mitigated by limiting duration of activity to avoid overheating and allowing sufficient time for recovery. To determine work/rest times for MWDs, temperature responses during training must be characterized. This study measured body core temperature of 48 MWDs at Lackland Air Force Base, San Antonio, TX. Twenty-four MWDs in training for patrol and detection activities participated under a range of ambient temperatures in August (27°C-32°C), October (22°C-26°C) and March (approximately 13°C). These MWDs swallowed a telemetric thermometer pill to measure continuous gastrointestinal tract temperature (Tgi). Twenty-four kennel MWDs participated in July (25°C-29°C). In these dogs rectal temperature (Tre) was measured manually during a standard exercise walk. For the MWDs in training, Tgi before the first activity was 38.5±0.5°C (mean±SD) and final Tgi was 39.8±0.6°C after sessions that lasted 13.1±4.9 minutes (5.4 to 26.3 minutes). Peak Tgi, 0.4±0.4°C above final Tgi, occurred 8 to 12 minutes into recovery. Before beginning a second activity 40 to 165 minutes later, Tgi was within 0.5°C of initial values for 80% of dogs. For the kennel MWDs, Tre was 39.0±0.8°C (37.7°C to 40.7°C) at the start and 40.1±0.6°C at the end of the 21.3±2.8 minute walk. The continuous increase in core temperature during activity of both groups of MWDs indicates that limiting exercise duration is important for minimizing risk of overheating in MWDs. The observation of continued increase in Tgi to a peak after exercise ends suggests that for MWDs suspected of overheating temperature should be monitored for at least 15 minutes postexercise to ensure recovery.

This study examined complex terrain march performance and cardiorespiratory responses when carrying different Soldier loads. Nine active duty military personnel (age, 21 ± 3 yr; height, 1.72 ± 0.07 m; body mass (BM), 83.4 ± 12.9 kg) attended two test visits during which they completed consecutive laps around a 2.5-km mixed terrain course with either a fighting load (30% BM) or an approach load (45% BM). Respiratory rate and heart rate data were collected using physiological status monitors. Training impulse (TRIMP) scores were calculated using Banister's formula to provide an integrated measure of both time and cardiorespiratory demands. Completion times were not significantly different between the fighting and approach loads for either Lap 1 (p = 0.38) or Lap 2 (p = 0.09). Respiration rate was not significantly higher with the approach load than the fighting load during Lap 1 (p = 0.17) but was significantly higher for Lap 2 (p = 0.04). However, heart rate was significantly higher with the approach load versus the fighting load during both Lap 1 (p = 0.03) and Lap 2 (p = 0.04). Furthermore, TRIMP was significantly greater with the approach load versus the fighting load during both Lap 1 (p = 0.02) and Lap 2 (p = 0.02). Trained military personnel can maintain similar pacing while carrying either fighting or approach loads during short mixed terrain marches. However, cardiorespiratory demands are greatly elevated with the approach load and will likely continue to rise during longer distance marches.

Cardiovascular (CV) and thermal responses to metabolically demanding multi-day military operations in extreme cold-weather environments are not well described. Characterization of these operations will provide greater insights into possible performance capabilities and cold injury risk. Soldiers from two cold-weather field training exercises (FTX) were studied during 3-day (study 1, n = 18, age: 20 ± 1 year, height: 182 ± 7 cm, mass: 82 ± 9 kg) and 4-day (study 2, n = 10, age: 20 ± 1 year, height: 182 ± 6 cm, mass: 80.7 ± 8.3 kg) ski marches in the Arctic. Ambient temperature ranged from −18 to −4 °C during both studies. Total daily energy expenditure (TDEE, from doubly labeled water), heart rate (HR), deep body (T pill), and torso (T torso) skin temperature (obtained in studies 1 and 2) as well as finger (T fing), toe (T toe), wrist, and calf temperatures (study 2) were measured. TDEE was 6821 ± 578 kcal day−1 and 6394 ± 544 for study 1 and study 2, respectively. Mean HR ranged from 120 to 140 bpm and mean T pill ranged between 37.5 and 38.0 °C during skiing in both studies. At rest, mean T pill ranged from 36.0 to 36.5 °C, (lowest value recorded was 35.5 °C). Mean T fing ranged from 32 to 35 °C during exercise and dropped to 15 °C during rest, with some T fing values as low as 6–10 °C. Ttoe was above 30 °C during skiing but dropped to 15–20 °C during rest. Daily energy expenditures were among the highest observed for a military training exercise, with moderate exercise intensity levels (~65% age-predicted maximal HR) observed. The short-term cold-weather training did not elicit high CV and T pill strain. T fing and T toe were also well maintained while skiing, but decreased to values associated with thermal discomfort at rest.

Introduction Dismounted military operations often involve prolonged load carriage over complex terrain, which can result in excessive metabolic costs that can directly impair soldiers' performance. Although estimating these demands is a critical interest for mission planning purposes, it is unclear whether existing estimation equations developed from controlled laboratory- and field-based studies accurately account for energy costs of traveling over complex terrain. This study investigated the accuracy of the following equations for military populations when applied to data collected over complex terrain with two different levels of load carriage: American College of Sports Medicine (2002), Givoni and Goldman (1971), Jobe and White (2009), Minetti et al (2002), Pandolf et al (1977), and Santee et al (2003). Materials and methods Nine active duty military personnel (age 21 ± 3 yr; height 1.72 ± 0.07 m; body mass 83.4 ± 12.9 kg; VO2 max 47.8 ± 3.9 mL/kg/min) were monitored during load carriage (with loads equal to 30% and 45% of body mass) over a 10-km mixed terrain course on two separate test days. The course was divided into four 2.5-km laps of 40 segments based on distance, grade, and/or surface factors. Timing gates and radio-frequency identification cards (SportIdent; Scarborough Orienteering, Huntington Beach, CA) were used to record completion times for each course segment. Breath-by-breath measures of energy expenditure were collected using portable oxygen exchange devices (COSMED Sri., Rome, Italy) and compared model estimates. Results The Santee et al equation performed best, demonstrating the smallest estimation bias (-13 ± 87 W) and lowest root mean square error (99 W). Conclusion Current predictive equations underestimate the metabolic cost of load carriage by military personnel over complex terrain. Applying the Santee et al correction factor to the Pandolf et al equation may be the most suitable approach for estimating metabolic demands in these circumstances. However, this work also outlines the need for improvements to these methods, new method development and validation, or the use of a multi-model approach to account for mixed terrain.

Background: Thermal safety standards for the use of chemical, biological, radiological, and nuclear (CBRN) ensembles have been established for various US occupations, but not for law enforcement personnel. Objectives: We examined thermal strain levels of 30 male US law enforcement personnel who participated in CBRN field training in Arizona, Florida, and Massachusetts. Methods: Physiological responses were examined using unobtrusive heart rate (HR) monitors and a simple thermoregulatory model to predict core temperature (Tc) using HR and environment. Results: Thermal strain levels varied by environments, activity levels, and type of CBRN ensemble. Arizona and Florida volunteers working in hot-dry and hot-humid environment indicated high heat strain (predicted max Tc.38.5uC). The cool environment of Massachusetts reduced thermal strain although thermal strains were occasionally moderate. Conclusions: The non-invasive method of using physiological monitoring and thermoregulatory modeling could improve law enforcement mission to reduce the risk of heat illness or injury.

OCCUPATIONAL APPLICATIONS A physiological status monitoring system was evaluated for use by soldiers in the field. Two different designs were evaluated, with the design based on previous human factors evaluations proven to be more comfortable and acceptable for use. This study demonstrated that the advanced design of the EQ-02 physiological status monitoring system met dismounted soldier needs. Furthermore, this study validated the use of a usability evaluation in the successful design/advancement of a physiological status monitoring system. TECHNICAL ABSTRACT Background: Previous research has shown that the form factor of a physiological status monitoring system, the Equivital™ EQ-01 (Hidalgo Ltd., Cambridge, UK) had problems associated with comfort and usability of the system for soldiers. Previous data gathered was used to guide improvements in the physiological status monitoring system. Purpose: Assess whether the previous feedback from usability evaluations helped guide improvements in comfort, accep...

This paper investigates the relationship between core temperature (T c), skin temperature (T s) and heat flux (HF) during exercise in hot conditions. Nine test volunteers, wearing an Army Combat Uniform and body armor, participated in three sessions at 25 °C/50 % relative humidity (RH); 35 °C/70 % RH; and 42 °C/20 % RH. Each session consisted of two 1-h treadmill walks at ~350 W and ~540 W intensity. T s and HF from six sites on the forehead, sternum, pectoralis, left rib cage, left scapula, and left thigh, and T c (i.e., core temperature pill used as a suppository) were measured. Multiple linear regressions were conducted to derive algorithms that estimate T c from T s and HF at each site. A simple model was developed to simulate influences of thermal conductivity and thickness of the local body tissues on the relationship between T c, T s, and HF. Coefficient of determination (R 2) ranged from 0.30 to 0.88, varying with locations and conditions. Good sites for T c measurement at surface were the sternum, and a combination of the sternum, scapula, and rib sites. The combination of T s and HF measured at the sternum explained ~75 % or more of variance in observed T c in hot environments. The forehead was found unsuitable for exercise in heat due to sweating and evaporative heat loss. The derived algorithms are likely applicable only for the same ensemble or ensembles with similar thermal and vapor resistances. Algorithms for T c measurement are location-specific and their accuracy is dependent, to a large degree, on sensor placement.

A real-time thermoregulatory model using noninvasive measurements as inputs was developed for predicting physiological responses of individuals working long hours. The purpose of the model is to reduce heat-related injuries and illness by predicting the physiological effects of thermal stress on individuals while working. The model was originally validated mainly by using data from controlled laboratory studies. This study expands the validation of the model with field data from 26 test volunteers, including US Marines, Australian soldiers, and US wildland fire fighters (WLFF). These data encompass a range of environmental conditions (air temperature: 19-30° C; relative humidity: 25-63%) and clothing (i.e., battle dress uniform, chemical-biological protective garment, WLFF protective gear), while performing diverse activities (e.g., marksmanship, marching, extinguishing fires, and digging). The predicted core temperatures (Tc), calculated using environmental, anthropometric, clothing, and heart rate measures collected in the field as model inputs, were compared with subjects' Tc collected with ingested telemetry temperature pills. Root mean standard deviation (RMSD) values, used for goodness of fit comparisons, indicated that overall, the model predictions were in close agreement with the measured values (grand mean of RMSD: 0.15-0.38° C). Although the field data showed more individual variability in the physiological data relative to more controlled laboratory studies, this study showed that the performance of the model was adequate.

This study assessed the human factors issues associated with wearing a Vital Sign Detection System (VSDS), a body worn physiological monitoring system. Experienced combat Soldiers ( n = 27) participated in a combat training exercise of ∼ 120 hr while wearing the VSDS. They were then given a questionnaire to assess comfort, physical impact on the body, and acceptability of the VSDS as well as questions on fit, impact on performance, and durability of the VSDS. Comfort was impacted the most by the VSDS when in the prone position, possibly affecting sleep, and prone position rifle shooting. Skin irritation or discomfort was reported in 85% of respondents. Sixty-two percent thought the VSDS was not acceptable to wear for ≥ 8 hr. Yet, at the same time, 92% of Soldiers approved of the concept for health monitoring, and 89% said they would wear the VSDS as is if it could help save their life. The VSDS needs to be modified to be more comfortable before it can be fielded for medical monitoring of Soldiers in the field.

Modern day dismounted military are commonly required to perform high physical work at high intensities in a variety of environmental conditions while facing challenging training and combat engagements. To optimize warfighter physical performance while providing protection from kinetic threats, tradeoffs must be made between physical performance and the adverse effects of the weight and functional characteristics of equipment and clothing carried and worn by the individual Soldiers. The work outlined in this report provides: 1) a quantitative assessment of the biophysical characteristics of three prototype body armor configurations, 2) a comparison to current baseline U.S. Army body armor systems, and 3) mathematical predictions of maximal work times in three different environmental conditions. This work provides a cost effective and scientifically valid method of making comparisons of clothing and equipment changes prior to conducting human research.

Mood state has been associated with performance in athletes; U.S. Army Rangers are the Army’s equivalent to the elite athlete. Purpose: To examine the relationship between mood and success on a qualification road march during Ranger School. Methods: Thirty-nine male Ranger students (mean ± sd; age, 25 ± 4 yrs; ht: 177 ± 5 cm, wt: 80 ± 9 kg; % body fat: 15 ± 4%, two-mile run fitness test: 12:50 ± 0:58 min) from two training classes participated. Road march distances were 8 and 12 miles for summer and winter classes, respectively. Environmental conditions were summer: 24.4° to 25.0°C air temperature (Ta), 82% to 89% relative humidity (RH), winter: -6.2°C to -4.4°C Ta and 51% to 60% RH. To achieve a passing grade and avoid being dropped from Ranger School, students needed to complete the march under a 16:25 min/mile pace while carrying ~31 kg of equipment. The Profile of Mood States (POMS) questionnaire was administered immediately after the march. The POMS assesses six moods (tension, depression, anger, vigor, fatigue, and confusion). Results: Road march times were 2:00 + 0:07 (hr:min) (avg 15:02 min/mile) for the 8-mile course and 3:03 + 0:12 (avg 15:15 min/mile) for the 12-mile course. A significant correlation between two-mile run times and road march times existed ( r = 0.80, p = 0.001 (summer) and r = 0.47, p = 0.05 (winter)). Correlations between mood and road march times were not significant for the winter class. However, significant correlations for tension r = 0.60; p = 0.004), depression: r = 0.60; p = 0.004), fatigue: r = 0.60; p = 0.004), and confusion: r = 0.53; p = 0.01) and road march times were seen in the summer class. Interaction effects from an analysis of variance between class (summer vs. winter) and passing the qualification standard (pass vs. fail) existed for tension ( p = 0.001), depression ( p = 0.28), fatigue ( p = 0.001), and confusion ( p = 0.022). Conclusions: Mood and performance were not related during the winter march. During the more environmentally- challenging summer march, mood was related to performance with more negative moods associated with those not meeting the U.S. Army Ranger School standard. The combined effects of the physical stress of completing the road march for time, the hotter environmental temperatures during the summer, and the disappointment of not meeting the Ranger School standard, likely contributed to these negative mood states.

The tactical law enforcement community is involved in a range of missions utilizing various types of personal protective equipment (PPE). They are also exposed to a wide range of environmental conditions. The use of chemical, biological, radiological, and nuclear (CBRN) protective ensembles, either with or without body armor, can add significant thermal stress due to the increased weight and insulating properties of these garments and head gear. High ambient heat conditions, especially with high solar loads, can lead to a rapid increase in body core temperature (TCore). When encapsulated in PPE, the rate of evaporative heat loss is substantially diminished which can lead to more rapid increases in TCore.

In order to estimate energy expended and metabolic heat produced during Border Patrol (BP) training or operations, 14 male BP personnel were studied over the course of a day. Energy expenditures in kilocalories (kcal) was determined for each activity by individual. Total energy expenditure for the work day (-7 hours) was then established and metabolic heat production estimated assuming mechanical 20% for human movement. It was found that BP personnel expended approximately 1750 plus or minus 540 kcal during their work day which would result in an estimated 24-hour daily energy expenditure of 3150 kcal. An average of 240 plus or minus 60 W of heat was produced over the entire work day (1 kcal/hr = 1.163 W). Peak metabolic heat production for activities lasting 30 minutes or longer was an estimated 360 plus or minus 204 W.

The Fluid Intake Monitor (FIM) measures fluid consumed from a bladder hydration system. Bench and field tests were performed to assess reliability and validity of the FIM, Fluid volumes of FIM were compared to scale-weighed volumes of water. Bench Test Results: an absolute percent error existed (p < 0.001) between sips, with the FIM significantly overestimating the first sip (p < 0.01) compared to the subsequent nine sips. A significant intraclass reliability coefficient (ICC) = 0.83 was achieved for trials 2 through 10. There was no difference in mean sip volume measured using the FIM vs. the scale (25.7 + 10.7 ml vs. 25.6 + 8.7 ml, respectively). Field Test Results: of 31 trials, 4 trials under-measured water consumption in excess of 15% (29.4% to 47.1%), and two trials over-measured water consumption in excess of 15% (15.5% and 16.6%). These units were neither reliable nor valid for use in the field. Software and hardware modifications identified should significantly improve FIM performance.

The U.S. Army Medical Department Board conducted a Customer Assessment of the Warfighter Physiological Status Monitor (WPSM) under USAMEDDBD Project 17-07, during July 23-27, 2007 at Camp Bullis, TX. The assessment primarily focused on whether WPSM triage information and use models proved beneficial to medics in assessing and providing care to simulated casualties, and examining the form and fit of two potential WPSM monitors. In addition during the customer assessment physiological data were collected by the two WPSM candidate monitors. The goal of this technical report is to provide a very quick analysis of the physiological data to aid the manufacturers as they continue to develop systems for field use.