THE EFFECTS OF WORK IN COOL AND HOT CONDITIONS ON PULSE RATE AND BODY TEMPERATURE

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Abstract
The effects of a hot environment on physical work have been studied in 10 subjocts, divided into two groups of eight. Both groups performed work daily for four hours in cool conditions for two weeks, and thon on one day in a hot environment, Thoroufter, both groups continued the daily work, one in hot conditions, the other in the cold, for a period of 12 days. Tho effects of work on pulse rate and body temperature have boon examined to dotormino the offect of the environmental conditions. Tho energy expenditure did not appoar to change throughout the experimont. In the cool environment, after approximately one week, post-work pulse rato and body tomperature remained relatively constant, and so wero the pulse rato and body temperature incromonts during work. On first exposure to heat, post-work body tomperature and pulso rato wore groater than in tho cool conditions. Body temporaturo and pulse rate increments wero also considerably largor. All four parameters decreasod with oach successive day of work in the hoat, but post-work pulso rate and body temporaturo did not reach the lovela attained in cool conditions. The pulso rate increment also remained higher, but body tomporaturo incremont fell to tho same value obsorvod in tho cold. Post-work pulso rate and body temporaturo are linoarly rolated, and a correction can be made to tho pulso rate by subtracting 27 beats/l°c for tho riso of body temporaturo above 37°c. The value so obtained is approximately equal to the post-work pulBe rate obsorved in cool conditions. It is concluded that assessing energy expenditure from post-work pulso rate or body temperature or their increments during work in tho hoat may bo misleading, as tho results will depend upon tho dogreo of acclimatization. If a correction ia made for tho lovol of body temporature, tho results indicate that an approximate measure of onergy expenditure can be made irrespective of tho state of acclimatization.