Effect of induced cyclic changes of deep body temperature on task performances.

Performance of three tests was studied during induced cycles of deep body temperature between limits of 37.8 degrees C and 38.9 degrees C. During heating phases skin temperature was 38.8 degrees C and during cooling it was 36.1 degrees C. A verbal transformation test, performed at the midpoint of each temperature cycle, showed no significant effect from the large differences in skin temperature and subjective comfort between heating and cooling. The test was considered to be insufficiently difficult. A pursuit rotor test and a colour/word interference test, performed at the end of the heating and cooling phases, showed mean decrements in performance of 15% and 4%, respectively. These results are related to the measured levels of deep body and skin temperature and to subjective assessments of comfort.