Decay of heat acclimation

Details

• Personal Author:
  Ashley CD ; Bernard, Thomas E. ; Ferron J
• Description:
  Acclimation can have a positive impact on heat tolerance. A period of time away from heat can result in the loss of the physiological adaptations of acclimation increasing the risk of heat illness, injury and death. The decay of acclimation has not been determined. PURPOSE: To examine the decay pattern of acclimation to heat. MEHODS: Participants (6 M, 6 F; BSA = 2.11 & 1.74 m2; max VO2 = 38.45 & 35.53 ml/kg/min) underwent an acclimation period by walking on a treadmill in a climatic chamber. Environmental conditions of the chamber were set at 50 degrees C and 20% rh. The treadmill speed and grade was set to elicit a moderate metabolic rate of approximately 40% max VO2. A 3-day plateau in core temperature (Tre) was used as evidence of acclimation. Participants were then randomly assigned to one of 2 decay groups. Group A returned for 1 acclimation session at 1,3 and 5 weeks post-acclimation. Group B returned for 1 acclimation session at 2,4 and 6 weeks post-acclimation. A repeated measures ANOVA was performed with levels of decay as the independent variable and end Tre, end heart rate (HR), sweat rate (SR) and tolerance time (TT) as the dependent variables. A trend analysis was used to examine the relationship between the independent and dependent variables. RESULTS: Average time for acclimation was 7 days. Tolerance time increased from the first to the final acclimation session (TT=88 & 112 min). There was a trend for a decrease in TT with increasing time away from the heat with TT equivalent for the first acclimation session and decay week 6. Other independent variables were not significant although there was a trend for an increase in end Tre with increased time away from heat. CONCLUSIONS: Complete decay of acclimation occurs after 6 weeks away from heat as evidenced by a decrease in TT and an increase in Tre. [Description provided by NIOSH]
• Subjects:
  Environmental Exposure Heat Stress Disorders Hot Temperature Men Occupational Health Risk Assessment Risk Factors Safety Women
• Keywords:
  Acclimatization Environmental-exposure Heat Heat-exposure Heat-stress Heat-tolerance Humans Injuries Physical-exercise Physical-fitness Physical-reactions Physiological-effects Physiological-function Physiology Risk-factors

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• ISSN:
  0195-9131
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  Florida ; OSHA Region 4
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  37
• Issue:
  5
• NIOSHTIC Number:
  nn:20044035
• Citation:
  Med Sci Sports Exerc 2005 May; 37(5)(Suppl 1):S401
• Federal Fiscal Year:
  2005
• Performing Organization:
  University of South Florida
• Peer Reviewed:
  False
• Start Date:
  20030930
• Source Full Name:
  Medicine and Science in Sports and Exercise
• Supplement:
  1
• End Date:
  20060929
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:2bf63f0e38691f12c2118b655cf5252d44999caf660491e1d86b9863e19324fff30ad025598b7deebfb49f81194ac1fc46707153cc3fdce62b8d481258b1f034
• Download URL:
  https://stacks.cdc.gov/view/cdc/199889/cdc_199889_DS1.pdf
• File Type:
  [PDF - 38.65 KB ]