PREDICTING HUMAN HEAT STRAIN AND PERFORMANCE WITH APPLICATION TO SPACE OPERATIONS

This Institute has developed a USARIEM Heat strain Prediction Model fo r predicting physiological responses and soldier performance in the he at, which has been programmed for use by handheld calculators and pers onal computers, and incorporated into the development of a hear strain decision aid. This model is demonstrated to predict accurately (gener ally within +/-1 SD/SEM) rectal temperature (Tie) responses for soldie rs wearing various military clothing ensembles during U.S. or non-U.S. military sce narios in the heat at home or abroad. The value of this model is shown presently for three NASA scenarios involving the Launch and Entry Suit (LES). The LES (ventilated or unventilated) is modeled during pre-launch/launch, re-entry/landing, and emergency egress afte r re entry/landing scenarios, predominately to evaluate heat acclimati on and hydration state effects. During the pre-launch/launch scenario, predicted final Tie closely agrees with observed values suggesting mi nimal heat strain (Tie similar to 38.0 degrees C). In contrast, dehydr ated (3%) unacclimated individuals show moderate levels of heat strain (Tre similar to 38.5 degrees C) for this same scenario. During the re -entry/landing and emergency egress scenarios, dehydrated unacclimated individuals are predicted to exhibit excessive heat strain (Tre > 39. 0 degrees C). Thermal tolerance time is predicted to be only 6 min dur ing emergency egress if individuals are: dehydrated and unacclimated t o heat while wearing the LES, If heat transfer values for space operat ions clothing are known, NASA can use this prediction model to help av oid undue heat strain involving astronauts for most scenarios during s paceflight.