Effect of Heat Acclimation on Sweat Minerals

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA480325&Location=U2&doc=GetTRDoc.pdf


This study examined the impact of 10 days of exercise-heat acclimation on sweat mineral concentrations.
Methods: Eight male subjects walked on a treadmill at 3.5 mph, 4% grade for 100 continuous minutes or until rectal temperature reached 39.5 C on 10 consecutive days in an environmental chamber set at 45 C, 20% relative humidity. Arm sweat samples were collected during the first 30 min of exercise-heat stress on days 1 and 10 using a polyethylene arm glove.
Results: Final core temperature and HR values were significantly lower (P < 0.05) on day 10 versus day 1. Whole-body sweating rates increased by approximately 6% (P = 0.12). Sweat sodium concentration on day 10 (36.22 + or - 7.22 mM) was significantly lower than day 1 (54.49 + or - 16.18 mM) (P < 0.05). Sweat mineral concentrations of calcium (~29%), copper
(~50%), and magnesium (~43%) were also significantly lower on day 10 versus day 1 of heat acclimation (P < 0.05). A trend for lower sweat iron (~75%; P = 0.07) and zinc (~23%; P = 0.10) concentrations were observed from day 1 to day 10. The estimated hourly sweat mineral losses (arm concentration x whole-body sweat rate) were reduced for calcium (~27%), copper
(~46%), and magnesium (~42%) (P <> 0.05), from day 1 to day 10. Conclusion: Exercise-heat acclimation conserves arm sweat mineral concentrations and possibly whole-body sweat losses of calcium,copper, and magnesium, and may reduce sweat iron and zinc concentrations.

An investigation of the Attenuation Provided by the Surefire EP3 Sonic Defender (Trademark) Earplug

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA485143&Location=U2&doc=GetTRDoc.pdf

The sound attenuation provided by the Surefire EP3 Sonic Defender(TM) earplug was determined in five males and five females. According to the manufacturer, an orifice in the plug allows safe sound levels to pass while lowering potentially harmful levels above 80 dBA from impulse noise by 35 dB. With the orifice closed the device performs like a conventional level-independent earplug. In each subject, hearing thresholds were measured at nine one-third octave noise band centre frequencies with the ears unoccluded and fitted with the Surefire EP3 with the orifice open and closed. Attenuation was defined as the difference between the protected and occluded thresholds. With the orifice closed attenuation increased non-monotonically from 14.5-31.0 dB from 0.125 kHz to 8 kHz. A decrease to 19.1 dB was evident at 4 kHz. With the orifice open attenuation increased from 4.4-27.0 dB with a decrease to 16.6 dB at 4 kHz and 6.3 kHz. The greatest differences due to mode of operation (9-10 dB) were observed at 0.125 and 0.25 kHz. There was no effect of gender of subjects. Comparison with the E-A-R Combat Arms earplug, which also has modes of operation for continuous and impulse noise indicated that the two devices were similar for the orifice open condition. For the orifice closed condition the Combat Arms earplug provided attenuation of 20.7-40.3 dB, on average 8 dB more than the Surefire EP3. Surefire EP3 attenuation was also compared with insertion loss measurements obtained using an acoustic test fixture. Insertion loss overestimated attenuation by approximately 16 dB in the range of 1 kHz to 6.3 kHz, regardless of mode of operation.

Considerations and Experiences in Developing a Finite Element Buttock Model for Seating Comfort Analysis

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA483758&Location=U2&doc=GetTRDoc.pdf


The comfort of seat cushions has become important in many of today’s high-performance USAF fighter and tactical aircraft. Experimental investigations have found that there exists a strong relationship between the human subjective discomfort rating for a seat cushion and the pressure distribution on the interface between the cushion and the buttocks. For the analysis of the contact pressure distribution, a finite element model of the human buttock was developed. The model consists of a detailed geometric description of the skin, soft tissues, and bony structures. The development of the model is described in this paper, which includes source data selection, bony structure modeling, joint modeling, soft tissue modeling, and pelvis shape morphing.

A Fatigue Management System for Sustained Military Operations

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA484144&Location=U2&doc=GetTRDoc.pdf


This research program consisted of four tasks, three of them specific research experiments. The fourth major objective was to extend the model of a software-based scheduling tool that predicts cognitive performance based on sleep and circadian patterns. The three experiments systematically evaluated the use and the impact of selected hypnotics and alertness medications to enhance operator performance during sustained military operations. The results for the first experiment were published in the January 2007 issue of Aviation, Space and Environmental Medicine. The findings demonstrated significant decrements in cognitive performance when
suddenly awakened while sleeping under the influence of zolpidem but not melatonin. Performance and polysomnography data from the second study evaluated the combined use of sleep aids (zolpidem or temazepam) and alertness aids (dextroamphetamine and melatonin)
to extend performance and alertness during a simulated 120-hour bomber surge operation. Performance under the Placebo condition deteriorated significantly during the latter portions of each of three successive 24-hour missions but not under the four drug-combination
conditions, which did not differ from each other throughout the missions. The third study demonstrated the potential efficacy of sublingual doses of flumazenil to reverse the soporific effects of zolpidem on performance in an operationally-relevant, sudden-awakening
paradigm. Publishable reports are in preparation for the latter two studies.

Motivational Interventions to Reduce Alcohol Use in a Military Population

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA484134&Location=U2&doc=GetTRDoc.pdf


The overriding objective of this research is to reduce hazardous drinking in a military sample by implementing two motivational interventions and comparing them to a treatment-as-usual condition. Individuals who are referred to the Air Force Alcohol and Drug Abuse Prevention and
Treatment (ADAPT) program as the result of an alcohol incident or who are self-referred are randomly assigned to one of three interventions: (1) a group motivational intervention, (2) an individual motivational intervention, or (3) a treatment-as-usual group. All participants provide
data regarding drinking and related problems at baseline and at 3, 6, and 12 months following the interventions. Analyses focus on (1) determining the effectiveness of the interventions in reducing alcohol use and alcohol-related problems, (2) testing factors that may mediate or moderate responses to the interventions, and (3) determining the cost and cost-effectiveness of treatment. The research includes a large sample and an extended follow-up on intervention effects, components that most previous intervention studies have lacked. From a practical perspective, the ability to classify which individuals will benefit from a motivational intervention
has important military readiness and alcohol policy implications.

Comparison of USARIEM Heat Strain Decision Aid to Mobile Decision Aid and Standard Army Guidelines for Warm Weather Training

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA483728&Location=U2&doc=GetTRDoc.pdf

Despite the US Army's comprehensive heat injury prevention program and widespread use and acceptance of guidance based on the wet bulb globe temperature index (WBGT), there were 5246 reported heat casualties in US Army Soldiers from 1980-2002. Of those, 75% occurred during scheduled military training at sites that followed WBGT based doctrine. There is a clear need for new methods to reduce the likelihood of heat casualties during military training. This report provides the basis for the following conclusions: (1) Since weather varies in time and space, best guidance will be obtained when model inputs are real-time weather measurements in the area of concern rather than estimated values. (2) The USARIEM heat strain decision aid (HSDA) is likely to be a more effective tool for reducing the risk of heat injury than simplifications derived from HSDA such as decision aids which use categorical weather input and the existing WBGT based Flag guidance (colored flag denotes WBGT heat category and associated heat injury prevention measures), and (3) Analysis of outcomes over a wide range of conditions should be used to further improve the performance of automated planning tools for warm weather training and these tools should be provided to Soldiers and their leaders

Thermal Comfort and Sensation in Men Wearing a Cooling System Controlled by Skin Temperature

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA484112&Location=U2&doc=GetTRDoc.pdf

The study was done to determine whether thermal comfort (TC), thermal sensation (TS), and subjective factors gauging environmental stress were negatively affected with different cooling methods in men exercising in chemical protective clothing. Background: Previous studies have reported that intermittent regional cooling improved the efficacy of cooling as compared with constant cooling (CC), but no studies have addressed whether there is any improvement in thermal comfort. Methods: Eight male volunteers exercised at moderate work intensity (425 W) in three microclimate cooling tests. The circulating fluid in the cooling garment was provided during exercise to the head (6% body surface area [BSA]), torso (22% BSA), and thighs (44% BSA) and manipulated under three methods: (a) CC, (b) pulsed cooling (PC), and (c) PC activated by mean skin temperature (Tsk) control (PCskin). TC and TS ratings were recorded every 20 min during the 80-min test. Results: TC and TS ratings were not different for PC skin and CC; thus the participants perceived PCskin as being similar to CC. TS were significantly warmer with PC than with PCskin and CC (p > .001), and PCskin was rated as being not as warm as PC according to TS. Conclusion: This indicates that the PCskin method was perceived as being as cool as CC and cooler than PC. Application: These findings indicate that the PCskin cooling method is an acceptable alternative to CC and PC based on human perceptions.