title: Influence of Chronic Heat Acclimatization on Occupational Thermal Strain in Tropical Field Conditions.
abstract: To examine whether non-heat acclimatized (NHA) emergency responders endure greater physiological and perceptual strain than heat acclimatized (HA) counterparts in tropical field settings.
  
  
  
  Eight HA and eight NHA men urban search and rescue personnel had physiological and perceptual responses compared during the initial 4 hours shift of a simulated disaster in tropical conditions (ambient temperature 34.0 °C, 48% relative humidity, wet bulb globe temperature [WBGT] 31.4 °C).
  
  
  
  From the 90th minute through to end of shift, HA (38.5 °C) sustained a significantly higher gastrointestinal temperature than NHA (38.1 °C) (mean difference 0.4 ± 0.2 °C, 95% confidence interval [CI] 0.2 to 0.7 °C, P = 0.005) despite comparable heart rate (P = 0.30), respiratory rate (P = 0.88), and axilla skin temperature (P = 0.47). Overall, perception of body temperature was similar between cohorts (P = 0.87).
  
  
  
  The apparent tolerance of greater physiological strain by HA responders occurred in the absence of perceptual differences.
authors.affiliation: National Critical Care and Trauma Response Centre, Level 8 Royal Darwin Hospital (Dr Brearley), Tiwi, NT, Australia; World Health Organisation (Dr Norton), Geneva, Switzerland; Queensland Fire and Emergency Services (Mr Rush, Mr Smith), Cannon Hill, Queensland; Northern Territory Fire and Rescue Service (Mr Hutton), Darwin, Northern Territory; Menzies School of Health Research (Ms Ward), Tiwi, Northern Territory; Princess Alexandra Hospital (Dr Fuentes), Woolloongabba, Queensland, Australia.
authors.forename: Matt B
authors.initials: MB
authors.lastname: Brearley
authors.forename: Ian
authors.initials: I
authors.lastname: Norton
authors.forename: Daryl
authors.initials: D
authors.lastname: Rush
authors.forename: Michael
authors.initials: M
authors.lastname: Hutton
authors.forename: Steve
authors.initials: S
authors.lastname: Smith
authors.forename: Linda
authors.initials: L
authors.lastname: Ward
authors.forename: Hector
authors.initials: H
authors.lastname: Fuentes
mesh_terms: D000064:Acclimatization; D000328:Adult; D001831:Body Temperature; D060731:Emergency Responders; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D000073397:Occupational Stress; D056152:Respiratory Rate; D012881:Skin Temperature; D013312:Stress, Physiological