Endurance of preheated men in exhausting work

F N Craig, H L Froehlich
1968 Journal of applied physiology  
II 2 DIGEST Illustrative data have been obtained to show how the capacity for exhausting work in a standard treadmill task can be degraded by initial overheating of the body. The endurance of men engaged in exhausting work on a treadmill is strongly influenced by the body temperature at the beginning of the work. The higher the initial rectal temperature, the shorter is the endurance. In three groups of four men, the regression of voluntary walking time on rectal temperature was highly
more » ... was highly significant, with coefficients of correlation of -0.96, -0.79, and -0.86, respectively. From these regressions it can be predicted that at an initial rectal temperature of 41°C, inen would be unable to work. Exhaustion appears to be reached at a maximal heart rate (average 201). The voluntary walking time is closely correlated with the standing heart rate before work is begun (-0.83). From the regression of walking time on standing heart rate, it is predicted that walking time would be zero at a standing heart rate of 205 beats per minute. Endurance of overheated men engaged in exhausting work appears to be limited by circulatory factors rather than by body temperature, for the average final heart rate only varied from 200 to 203, whereas the final rectal temperature varied from 37.6 to 39.2°C when the men were subjected to different degrees of initial overheating. When the endurance was diminished by overheating, the wearing of the M17 field protective mask did not alter the endurance, perhaps because maximal work rates were not attained. In order to maintain the maximum capacity for exhauisting work, troops in the field must avoid overheating as well as dehydraticn. j3
doi:10.1152/jappl.1968.24.5.636 pmid:5647640 fatcat:ofkbdxxjgbaodewvllibbdviou