Loss of heat acclimation and time to re-establish acclimation

Details

• Personal Author:
  Ashley CD ; Bernard, Thomas E. ; Ferron J
• Description:
  Acclimation in a hot environment is one potent means to decrease the heat strain of work in a hot environment. However, with diminished heat exposure, positive adaptations of acclimation may be lost. This rate of loss is equivocal and, cone established, could be used to prescribe the time for re-acclimation. The purpose of this study was to determine the rate of loss of heat acclimation over a period of 6 weeks and determine the time needed for re-acclimation after 2 weeks and 4 weeks of de-acclimation in ten healthy participants. All participants first underwent an initial acclimation period [a 3-day plateau in T(re) was used to signify acclimation]. Based on the mean time to acclimate in Phase 1 (mean time to acclimate = 6.1+/-1.4 days), the loss of acclimation was mapped and participants were randomly assigned to one of two groups: one that underwent one 2-hour heat exposure at 1,3 and 5 weeks post-acclimation, and one that underwent one 2-hour heat exposure session at 2,4 and 6 weeks. Complete loss of acclimation occurred in 6 weeks and, as expected work HR and T(re) increased with increasing time away from the heat (p<0.05). Based on the time for total loss of acclimation from Phase 1, participants in Phase 2 (n=8) first underwent acclimation. Then, after either a 2-week or 4-week absence from the heat, participants returned to the laboratory for re-acclimation. While not statistically significant yet practically significant (p=0.18; one-tailed confidence interval), average days for re-acclimation in the 2-week group tended to be fewer than in the 4-week group (days for re-acclimation = 3.8+/-1.2 and 5.3+/-1.9, respectively). Based on these general trends, for occupational settings, a re-acclimation period of 4 days is recommended after two weeks absence from the heat, 5 days for four weeks absence from the heat and complete acclimation (6 days) after 6 weeks absence or more from the heat. [Description provided by NIOSH]
• Subjects:
  Environmental Exposure Environmental Monitoring Hot Temperature Occupational Health Safety Workplace
• Keywords:
  Acclimation Acclimatization Adaptation Author Keywords: Heat Decay Environmental-exposure Exposure-assessment Heat Heat-exposure Heat-loss Heat-reduction Heat-tolerance Hot-environments Humans Physiological-effects Re-acclimation Work-environment

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• ISSN:
  1545-9624
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Florida ; OSHA Region 4
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  302-308
• Volume:
  12
• Issue:
  5
• NIOSHTIC Number:
  nn:20045624
• Citation:
  J Occup Environ Hyg 2015 May; 12(5):302-308
• Contact Point Address:
  Candi D. Ashley, University of South Florida, College of Education, 4202 E. Fowler Ave., Tampa, FL USA 33620-8600
• Email:
  cashley@usf.edu
• Federal Fiscal Year:
  2015
• Performing Organization:
  University of South Florida
• Peer Reviewed:
  True
• Start Date:
  20030930
• Source Full Name:
  Journal of Occupational and Environmental Hygiene
• End Date:
  20060929
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:fb6ad2df2081e7b3df574a88f884ce3a434653d7434546aafc9a0c92c20af0bbaa21997ff4b2472146eaad256333024bbbdf657d4e055b50a877bc2e2bbdcdc2
• Download URL:
  https://stacks.cdc.gov/view/cdc/200977/cdc_200977_DS1.pdf
• File Type:
  [PDF - 104.16 KB ]