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Daniel S. Moran, Yuval Heled, Lawrence Still, Arie Laor, Yair Shapiro
Med Sci Monit 2004; 10(6): CR252-257
Background:The aim of this study was to evaluate the heat tolerance test, which was performed by individuals with high risk for heat injuries, for exposure duration and climatic conditions.Material/Methods: Nineteen young (19±1 yr) post heat stroke males performed 2 separate tolerance tests consisting of identical treadmill walking (5km·h–1, 2% grade) for 120 min during hot (40°C, 40%RH) and comfort (20°C, 50%RH) climate conditions. Physiological monitoring included rectal temperature (T[sub]re[/sub]), heart rate (HR), skin temperature and sweat rate (m[sub]sw[/sub]). Concomitantly, strain evaluation was assessed by the physiological strain index (PSI) and the cumulative heat strain index (CHSI).Results: 14 subjects were categorized as heat tolerant (HT) and 5 subjects as heat intolerant (HI). The comfort tolerance test was found as irrelevant for heat intolerance assessment. PSI after 60 min (PSI[sub]60[/sub]) was unable to predict PSI after 120 min (PSI[sub]120[/sub]) whereas there was not a high enough correlation between CHSI[sub]60[/sub] and CHSI[sub]120[/sub].
Conclusions: It was concluded that tolerance to heat must be tested during heat stress and the test duration cannot be shorter than 120 min.