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December 7, 1957


JAMA. 1957;165(14):1813-1818. doi:10.1001/jama.1957.02980320043010

The incidence of heat casualties among recruits at a training center has been reduced appreciably since 1953 by limiting certain activities during periods of excessive heat. To avoid undue loss of time from programs of drill and physical conditioning, a closer adaptation of such activities to weather conditions was needed. An older index based on temperature and humidity alone was replaced by an index (WBGT) based on temperatures read with a shaded dry bulb thermometer, a shaded wet bulb thermometer, and a "globe" consisting of a thermometer enclosed within an unshaded, blackened 6-in. copper sphere. The closer adjustment of the training program to weather resulted in a further significant reduction of heat casualties in the summer of 1956, although it was hotter than the summer of 1955.