[The dynamic indices of human thermal status during overheating exposures]

The thermal state of 7 naked test subjects on a 25 min of work (325 J/s) at 40 degrees C and 85% humidity of the ambient air has exceeded the acceptable limits. The thermal protecting garment having high thermal resistance indices was tested near a fire source. The subjects performed the 254 J/s and 403 J/s work so long as they were able to do it. Time of work was, on average, 17 and 12 min, respectively. By the end of work, thermal state of the subjects approached to a "limiting" value: heart rate and rectal temperature were, on average, 160-170 beats/min, and 38.3 degrees C, respectively. Three patterns of dynamics of core temperature of the body measured immediately after terminating the work have been observed. In the most experiments during first 5 min after leaving a fire zone there occurred a further temperature rise (by 0.2-0.5 degrees C). The conditions and levels of physiological indices at which there was a postwork incremental hyperthermia which is of prognostic significance have been determined. Among reasons of this phenomenon there can be a delay of thermal production from an increased oxygen consumption under conditions of ergothermal load, a reduced circulation and a surface-to-core heat transfer.