Heat-acclimated, lightly clothed men and women (four of each) walked on a treadmill at 25% and 43% VO2 max, respectively, (M =194 W.m-2), under seven air temperatures (Ta) ranging from 36 to 52 degrees C. Each experiment involved 1 h of fixed and a 2nd h of progressively increasing ambient vapor pressure (Pa). The relative steady state of rectal temperature (Tre), mean skin temperature (Tsk), and heart rate (HR) reached in the 1st h were forced upward during the 2nd h by the rising Pa. The critical air vapor pressure (Pcrit) was identified by the Tre point of inflection for each Ta. One man did not fully reach steady state, but inflection could be determined for his physiological responses. The mean values of all points of inflection were calculated for Tre, Tsk, and HR. Significant sex difference in HR was found only by excluding the results of the one man. Tre and Tsk showed no significant difference between men and women. The coefficient for evaporative heat transfer (he), which could be derived using the Pcrit for the low Ta range, was 14.5 +/- 2.2 W.m-1 Torr-1.
Five minutes of carrying loads uphill were assigned to three female and three male heat acclimated subjects. The carrying (75% [Formula: see text]), both of which were performed under warm-humid Tdb 36°C, Twb 31°C, and hot-dry Tdb 50°C, Twb 25°C, ambient conditions. Thirty minutes of rest were allowed after each 30 minutes of work. The resting conditions were either the same as those for the working periods or under neutral ambient conditions. Judged by the rise in HR and in Tre, and setting the limits of Tre to 38°C during the walking, the schedule was adequate only when resting was under the neutral ambient conditions, it was partially adequate for resting under the hot-dry ambient conditions, but completely inadequate for resting under the warm-humid conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.