Abstract
After an initial review of previous work, the results of experiments designed to show the effects of elevated environmental temperature and humidity on selected human psychomotor tasks recommended by the International Biological Program are presented. Previous work in this field has led to conflicting results using mainly male subjects. 17 male and 47 female unacclimatised subjects were used in the present experiments. Two temperature conditions, 40C and 35C D. B. at 50% relative humidity (30. 5C and 26. 2C W. B. ) with negligible radiant heat load, at a mean air velocity of 33. 6 cm/sec were studied in two climatic chambers. The results obtained showed that the females tolerated the acute exposures to a greater level than the males, as recorded by measurements of tympanic membrane temperature. Few increments or decrements in performance were observed in either sex on the perceptual-motor tasks, although reduced sensory stimulation as evidenced by visual acuity under heat stress, brought about a significant increase in performance in a block---threading task. Ancilliary experiments with reduced illumination levels under heat stress were carried out in order to examine this phenomenum further, with conflicting results. Additional tests were also carried out in an attempt to relate subcutaneous fat as measured by skinfold thickness, incorporated into the Heath-Carter Somatotype Rating, to the rise in body core temperature with time. The results failed to demonstrate the previously observed phenomenon of the females' increased tolerance to the acute heat exposure.