United States Army Research Institute of Environmental Medicine: Warfighter research focusing on the past 25 years.

The United States Army Research Institute of Environmental Medicine (USARIEM) celebrated its 50th anniversary on July 1, 2011. This article reviews its history, evolution, and transition of its research programs as well as its scientific and military accomplishments, emphasizing the past 25 yr. During the 1990s, USARIEM published a series of pocket guides providing guidance for sustaining Warfighter health and performance in Southwest Asia, Somalia, the former Republic of Yugoslavia, Rwanda, and Haiti.

Combined environmental stress and physiological strain indices for physical training guidelines.

The purpose of this study was to develop guidelines based on the previously described environmental stress index (ESI) and physiological strain index (PSI) for work-rest cycles (WRC) during training, especially in the military. The ESI was introduced as a potential substitute for the Wet Bulb Globe Temperature Index because of the very high correlation coefficients between them. The ESI is constructed from the fast-reading meteorological response sensors ambient temperature (Ta), relative humidity (RH), and global radiation (GR), which require only a few seconds to reach equilibrium.

Evaluation and refinement of the environmental stress index for different climatic conditions.

The purpose of this study was to evaluate the recently constructed environmental stress index (ESI) for a large database comprising various climatic conditions. Data analysis of measurements from 19 locations revealed a high correlation between ESI and the wet bulb globe temperature (WBGT) index for each database. Validity from statistical analysis, including optimization procedures, slightly changed the ESI constants as follows: ESI = 0.

Aging and assessment of physiological strain during exercise-heat stress.

The purpose of this study was to evaluate the physiological strain index (PSI) for different age groups during exercise-heat stress (EHS). PSI was applied to three different databases. First, from young and middle-age men (21 +/- 2 and 46 +/- 5 yr, respectively) matched (n = 9 each, P > 0.

Cold strain index applied to exercising men in cold-wet conditions.

A cold strain index (CSI) based on rectal (T(re)) and mean skin temperatures ((sk)) using data from seminude resting subjects has been proposed (Moran DS, Castellani JW, O'Brien C, Young AJ, and Pandolf KB. Am J Physiol Regulatory Integrative Comp Physiol 277: R556-R564, 1999). The current study determined whether CSI could provide meaningful data for clothed subjects exercising in the cold with compromised insulation.

Role of core temperature as a stimulus for cold acclimation during repeated immersion in 20 degrees C water.

The relative importance of skin vs. core temperature for stimulating cold acclimation (CA) was examined by 5 wk of daily 1-h water immersions (20 degrees C) in resting (RG) and exercising (EG) subjects. Rectal temperature fell (0.

Effects of dehydration, hypohydration, and hyperhydration on tolerance during uncompensable heat stress.

The present study examined the effects of dehydration from prior exercise on subsequent exercise tolerance time (TT) that involved wearing nuclear, biological, and chemical (NBC) protective clothing. It was hypothesised that TT would be reduced in the dehydrated state. Ten men undertook continuous treadmill walking at 4.

Evaluating physiological strain during cold exposure using a new cold strain index.

A cold strain index (CSI) based on core (T(core)) and mean skin temperatures (T(sk)) and capable of indicating cold strain in real time and analyzing existing databases has been developed. This index rates cold strain on a universal scale of 0-10 and is as follows: CSI = 6.67(T(core t) - T(core 0)).

Simulation of a cold-stressed finger including the effects of wind, gloves, and cold-induced vasodilatation.

The thermal response of fingers exposed to cold weather conditions has been simulated. Energy balance equations were formulated, in a former study, for the tissue layers and the arterial, venous, and capillary blood vessels. The equations were solved by a finite difference scheme using the Thomas algorithm and the method of alternating directions.

Can gender differences during exercise-heat stress be assessed by the physiological strain index?

A physiological strain index (PSI) based on rectal temperature (Tre) and heart rate (HR) was recently suggested to evaluate exercise-heat stress. The purpose of this study was to evaluate PSI for gender differences under various combinations of exercise intensity and climate. Two groups of eight men each were formed according to maximal rate of O2 consumption (VO2 max).

Wet bulb globe temperature (WBGT)--to what extent is GT essential?

Background: Industrial and military safety personnel often require an easy, quick and accurate assessment of heat stress as a potential risk. The widely used WBGT index to evaluate heat stress is cumbersome and suited for a fixed site station rather than a mobile situation. Recently, a modified discomfort index (MDI) compiled from ambient temperature (Ta) and wet bulb temperature (Tw) was suggested to evaluate heat stress.

The physiological strain index applied to heat-stressed rats.

A physiological strain index (PSI) based on heart rate (HR) and rectal temperature (Tre) was recently suggested to evaluate exercise-heat stress in humans. The purpose of this study was to adjust PSI for rats and to evaluate this index at different levels of heat acclimation and training. The corrections of HR and Tre to modify the index for rats are as follows: PSI = 5 (Tre t - Tre 0).

Does erythrocyte infusion improve 3.2-km run performance at high altitude?

The effects of autologous erythrocyte infusion on improving exercise performance at high altitude have not previously been studied. The effects of erythrocyte infusion on 3.2-km (2-mile) run performance were evaluated during 3 days (HA3) and 14 days (HA14) exposure to high altitude (4300 m) in erythrocyte-infused (ER) and control (CON) subjects that were initially matched (P>0.

Evaluation of different levels of hydration using a new physiological strain index.

A physiological strain index (PSI), based on rectal temperature (Tre) and heart rate (HR), was recently suggested for evaluating heat stress. The purpose of this study was to evaluate the PSI for different combinations of hydration level and exercise intensity. This index was applied to two databases.

Time course of heat acclimation and its decay.

More is known about the time course for the acquisition of human heat acclimation during exercise than its decay or loss. Pioneering research in the 1940s led to our early understanding of the heat acclimation process and its subsequent decay with further knowledge concerning the associated physiological mechanisms in later years. For both hot-dry and hot-humid environments, nearly complete exercise-heat acclimation occurs after 7 to 10 days of exposure.

A physiological strain index to evaluate heat stress.

A physiological strain index (PSI), based on rectal temperature (Tre) and heart rate (HR), capable of indicating heat strain online and analyzing existing databases, has been developed. The index rates the physiological strain on a universal scale of 0-10. It was assumed that the maximal Tre and HR rise during exposure to exercise heat stress from normothermia to hyperthermia was 3 degrees C (36.

Human thermoregulatory responses during serial cold-water immersions.

This study examined whether serial cold-water immersions over a 10-h period would lead to fatigue of shivering and vasoconstriction. Eight men were immersed (2 h) in 20 degrees C water three times (0700, 1100, and 1500) in 1 day (Repeat). This trial was compared with single immersions (Control) conducted at the same times of day.

Hyperhydration: tolerance and cardiovascular effects during uncompensable exercise-heat stress.

This study examined the efficacy of glycerol and water hyperhydration (1 h before exercise) on tolerance and cardiovascular strain during uncompensable exercise-heat stress. The approach was to determine whether 1-h preexercise hyperhydration (29.1 ml H2O/kg lean body mass with or without 1.

Heat strain models applicable for protective clothing systems: comparison of core temperature response.

Core temperature (Tc) output comparisons were analyzed from thermal models applicable to persons wearing protective clothing. The two models evaluated were the United States (US) Army Research Institute of Environmental Medicine (USARIEM) heat strain experimental model and the United Kingdom (UK) Loughborough (LUT25) model. Data were derived from collaborative heat-acclimation studies conducted by three organizations and included an intermittent-work protocol (Canada) and a continuous-exercise/heat stress protocol (UK and US).

Hyperhydration: thermoregulatory effects during compensable exercise-heat stress.

This study examined the effects of hyperhydration on thermoregulatory responses during compensable exercise-heat stress. The general approach was to determine whether 1-h preexercise hyperhydration [29. 1 ml/kg lean body mass; with or without glycerol (1.

Numerical analysis of an extremity in a cold environment including countercurrent arterio-venous heat exchange.

A model of the thermal behavior of an extremity, e.g., a finger, is presented.

Thermal and metabolic responses to cold-water immersion at knee, hip, and shoulder levels.

To examine the effect of cold-water immersion at different depths on thermal and metabolic responses, eight men (25 yr old, 16% body fat) attempted 12 tests: immersed to the knee (K), hip (H), and shoulder (Sh) in 15 and 25 degrees C water during both rest (R) or leg cycling [35% peak oxygen uptake; (E)] for up to 135 min. At 15 degrees C, rectal (Tre) and esophageal temperatures (Tes) between R and E were not different in Sh and H groups (P > 0.05), whereas both in K group were higher during E than R (P < 0.