A unified system for evaluation and selection of heat stress candidates

¹ Biomedical Laboratory, Aerospace Medical Division, Wright-Patterson Air Force Base, Ohio

A system for the evaluation and selection of heat stress candidates has been developed that is concerned not only with the extent to which an individual is capable of dissipating heat, but also the price he must pay for so doing. The former is dealt with through the concept of effective body heat storage (q_e); the latter, through a newly developed index of strain (I_G). Effective body heat storage is defined as that amount of storage obtained if a subject were able to go into a heat chamber already fully equilibrated with it and with all heat-dissipating mechanisms fully operating. The index attempts to express a new concept, accumulative circulatory strain, in terms of heart rate alone. The best subjects (usually in the young age groups) show a low q_e and low I_G; the worst (usually in the older age groups) show a high q_e and low I_G. All subjects were maintained at rest during heat exposure.