Authors: Bernhard Kampmann Peter Bröde Martin Schütte Barbara Griefahn
Publish Date: 2008/01/10
Volume: 104, Issue: 2, Pages: 321-327
Abstract
The decrease in resting core temperature T co and its relation to the reduced physiological strain during heat acclimation was analysed with rectal temperature data measured in three groups of eight seminude persons 6 males 2 females who were acclimated for 15 consecutive days to dry humid and radiant heat respectively with equivalent WBGT 335°C by performing 2h treadmill work A fourth group followed the same protocol for 12 days in a neutral climate After acclimation both resting T co prior to heat exposure and final T co measured at the end of work were significantly reduced The reduction in final T co increased with decreasing ambient water vapour pressure and was higher for the data pooled over the heat conditions 046 ± 031°C than in the neutral climate 021 ± 025°C whereas resting T co declined similarly in the heat 020 ± 025°C and the neutral environment 017 ± 023°C The lowering of resting and final T co after heat acclimation showed a significant correlation r = 067 and regression analysis showed that 37 of the average reduction in final T co was attributable to the lowering of resting T co The same analysis was applied after extending the database by shortterm series of clothed persons 17 females 16 males acclimated at 295 and 315°C WBGT for 5 days A significant correlation was found between the lowering of resting and final T co r = 057 that did not depend on climatic conditions and gender although the reduction in resting T co was significantly smaller for females 006 ± 022°C than for males 021 ± 023°C It is concluded that the lowering of resting core temperature contributes to the reduced physiological strain during heat acclimation Similar effects under neutral conditions point to the exercise stimulus as a probable explanation
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