Cross validation of USARIEM heat strain prediction models

Hypothesis: This study was a cross validation of three heat strain predicti on models developed at the U.S. Army Research institute of Environmental Me dicine: the ARIEM, HSDA, and ARIEM-EXP models ability to predict core tempe rature. Methods: Seven heat-acclimated subjects completed twelve experiment al tests, six in each of two hot climates, at three exercise intensities an d two uniform configurations in each climate. Results: Experimental results showed physiological responses as expected with heat strain increasing wit h work load and level of protective clothing, but with similar heat strain between the two environments matched for wet bulb, globe index. Neither the ARIEM or HSDA model closely predicted core temperatures over the course of the experiment, due mostly to an abrupt initial rise in core temperature i n both models. A proportionality constant in the ARIEM-EXP buffered some of this abrupt rise. Conclusions: Comparisons of the core temperature and tol erance times data with the three models led to the conclusions that for hea lthy males: 1) the ARIEM and HSDA models provide conservative safety limits as a result of predicting rapid initial increases in core temperature; 2) the ARIEM-EXP most closely represents core temperature responses; 3) the AR IEM-EXP requires modifications with an alternate proportionality coefficien t to increase accuracy for low metabolic cost exercise; 4) all of the model s require additional input from existing research on tolerance to heat stra in to better predict tolerance times; and 5) additional models should be ex amined to investigate the transient state of the body as it is affected by environment, clothing and exercise.