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Seasonal heat acclimatization in wildland firefighters.
J Therm Biol 2014; 45:134-40JT

Abstract

The purpose of this study was to determine changes in physiological markers of heat acclimatization across a 4-month wildland fire season. Wildland firefighters (WLFF) (n=12) and non-WLFF (n=14) were assessed pre- and post-season for body mass, percent body fat, and peak VO₂. Both groups completed a 60-min heat stress trial (walking at 50% of peak VO₂) in a climate controlled chamber (43.3 °C, 33% RH) pre and post-fire season (May through September). During the trials, core (Tc) and skin (Tsk) temperatures, heart rate (HR), physiological strain index (PSI), and rating of perceived exertion (RPE) were measured. There were no differences pre or post-season between the WLFF and non-WLFF groups in body mass, percent body fat, or peak V.O2. During the 73 days where the WLFF were involved in direct wildland fire suppression, daily high temperature for the WLFF was higher compared to the non-WLFF, 30.6 ± 5.4 °C and 26.9 ± 6.1 °C, respectively, p<0.05. Tc was lower at post-season compared to pre-season (p<0.05) for the WLFF at 30, 45, and 60 min (pre 30, 45, and 60: 37.9 ± 0.3, 38.3 ± 0.3 and 38.5 ± 0.3 °C, respectively; post 30, 45, and 60: 37.8 ± 0.3, 38.1 ± 0.3 and 38.2 ± 0.4 °C, respectively). For WLFF, PSI was lower (p<0.05) at 15, 30, 45, and 60 min at post-season compared to pre-season (4.2 ± 0.7, 5.6 ± 0.9, 6.5 ± 0.9, and 7.1 ± 1.1 for 15, 30, 45, and 60 min pre-season, respectively; 3.6 ± 0.8, 4.9 ± 1.0, 5.7 ± 1.2, 6.3 ± 1.3 for 15, 30, 45, and 60 min post-season, respectively). For WLFF, RPE was lower during the post-season trial at 30, 45, and 60 min (pre 30, 45, and 60: 11.7 ± 1.4, 12.3 ± 1.2, and 13.5 ± 1.4, respectively; post 30, 45, and 60: 10.7 ± 1.2, 11.3 ± 1.3, and 11.9 ± 1.5, respectively), p<0.05. There were no differences between pre and post-season for the non-WLFF for Tc and PSI, but RPE was lower at 15 min during the pre-season trial. WLFFs demonstrated significant decreases in Tc, PSI, and RPE during controlled heat stress after the season. Since an age and fitness-matched control group experienced no indication of heat acclimatization, it is suggested that the long-term occupational heat exposure accrued by the WLFFs was adequate to incur heat acclimatization.

Authors+Show Affiliations

Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, 32 Campus Drive, Missoula, MT 59812-1825, United States. Electronic address: brianna.lui@umontana.edu.Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, 32 Campus Drive, Missoula, MT 59812-1825, United States. Electronic address: john.cuddy@mso.umt.edu.Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, 32 Campus Drive, Missoula, MT 59812-1825, United States. Electronic address: walter.hailes@mso.umt.edu.Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, 32 Campus Drive, Missoula, MT 59812-1825, United States. Electronic address: brent.ruby@mso.umt.edu.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

25436962

Citation

Lui, Brianna, et al. "Seasonal Heat Acclimatization in Wildland Firefighters." Journal of Thermal Biology, vol. 45, 2014, pp. 134-40.
Lui B, Cuddy JS, Hailes WS, et al. Seasonal heat acclimatization in wildland firefighters. J Therm Biol. 2014;45:134-40.
Lui, B., Cuddy, J. S., Hailes, W. S., & Ruby, B. C. (2014). Seasonal heat acclimatization in wildland firefighters. Journal of Thermal Biology, 45, pp. 134-40. doi:10.1016/j.jtherbio.2014.08.009.
Lui B, et al. Seasonal Heat Acclimatization in Wildland Firefighters. J Therm Biol. 2014;45:134-40. PubMed PMID: 25436962.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Seasonal heat acclimatization in wildland firefighters. AU - Lui,Brianna, AU - Cuddy,John S, AU - Hailes,Walter S, AU - Ruby,Brent C, Y1 - 2014/09/01/ PY - 2014/02/26/received PY - 2014/08/27/revised PY - 2014/08/27/accepted PY - 2014/12/2/entrez PY - 2014/12/2/pubmed PY - 2015/8/6/medline KW - Heat injury KW - Heat stress KW - Heat-related illness KW - Physiological strain index SP - 134 EP - 40 JF - Journal of thermal biology JO - J. Therm. Biol. VL - 45 N2 - The purpose of this study was to determine changes in physiological markers of heat acclimatization across a 4-month wildland fire season. Wildland firefighters (WLFF) (n=12) and non-WLFF (n=14) were assessed pre- and post-season for body mass, percent body fat, and peak VO₂. Both groups completed a 60-min heat stress trial (walking at 50% of peak VO₂) in a climate controlled chamber (43.3 °C, 33% RH) pre and post-fire season (May through September). During the trials, core (Tc) and skin (Tsk) temperatures, heart rate (HR), physiological strain index (PSI), and rating of perceived exertion (RPE) were measured. There were no differences pre or post-season between the WLFF and non-WLFF groups in body mass, percent body fat, or peak V.O2. During the 73 days where the WLFF were involved in direct wildland fire suppression, daily high temperature for the WLFF was higher compared to the non-WLFF, 30.6 ± 5.4 °C and 26.9 ± 6.1 °C, respectively, p<0.05. Tc was lower at post-season compared to pre-season (p<0.05) for the WLFF at 30, 45, and 60 min (pre 30, 45, and 60: 37.9 ± 0.3, 38.3 ± 0.3 and 38.5 ± 0.3 °C, respectively; post 30, 45, and 60: 37.8 ± 0.3, 38.1 ± 0.3 and 38.2 ± 0.4 °C, respectively). For WLFF, PSI was lower (p<0.05) at 15, 30, 45, and 60 min at post-season compared to pre-season (4.2 ± 0.7, 5.6 ± 0.9, 6.5 ± 0.9, and 7.1 ± 1.1 for 15, 30, 45, and 60 min pre-season, respectively; 3.6 ± 0.8, 4.9 ± 1.0, 5.7 ± 1.2, 6.3 ± 1.3 for 15, 30, 45, and 60 min post-season, respectively). For WLFF, RPE was lower during the post-season trial at 30, 45, and 60 min (pre 30, 45, and 60: 11.7 ± 1.4, 12.3 ± 1.2, and 13.5 ± 1.4, respectively; post 30, 45, and 60: 10.7 ± 1.2, 11.3 ± 1.3, and 11.9 ± 1.5, respectively), p<0.05. There were no differences between pre and post-season for the non-WLFF for Tc and PSI, but RPE was lower at 15 min during the pre-season trial. WLFFs demonstrated significant decreases in Tc, PSI, and RPE during controlled heat stress after the season. Since an age and fitness-matched control group experienced no indication of heat acclimatization, it is suggested that the long-term occupational heat exposure accrued by the WLFFs was adequate to incur heat acclimatization. SN - 0306-4565 UR - https://www.unboundmedicine.com/medline/citation/25436962/Seasonal_heat_acclimatization_in_wildland_firefighters_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0306-4565(14)00125-9 DB - PRIME DP - Unbound Medicine ER -