Work Patterns Dictate Energy Demands and Thermal Strain During Wildland Firefighting

John S. Cuddy, Joseph A. Sol, Walter S. Hailes, Brent C. Ruby

Research output: Contribution to journalArticlepeer-review

68 Scopus citations


Objective The purpose of this investigation was to characterize the effects of self-selected work activity on energy expenditure, water turnover, and thermal strain during wildland fire suppression. A secondary aim was to contrast current data with data collected 15 years ago using similar methods to determine whether job demands have changed. Methods Participants (n = 15, 26 ± 3 years, 179 ± 6 cm, 78.3 ± 8.6 kg) were monitored for 3 days for total energy expenditure, water turnover, core and chest skin temperature, physical activity, and heart rate. Participants arrived to the mobile laboratory each morning, submitted a nude weight, ingested a temperature transmitter, provided a urine sample, and were equipped with a physiological and activity monitor. Participants completed live wildland fire suppression during their work shifts. Results Mean core temperature was 37.6 ± 0.2 C, mean chest skin temperature was 34.1 ± 1.0 C, mean heart rate was 112 ± 13 beats/min, and the mean physiological strain index score was 3.3 ± 1.0. Wildland firefighters spent 49 ± 8%, 39 ± 6%, and 12 ± 2% in the sedentary, light, and moderate-vigorous intensity categories, respectively. The mean total energy expenditure was 19.1 ± 3.9 MJ/d, similar to 1997 (17.5 ± 6.9 MJ/d). The mean water turnover in 2012 was 9.5 ± 1.7 L/d, which was higher (P <.05) compared with 1997-98 (7.0 ± 1.7 L/d). Conclusions Wildland firefighters do not induce consistently high cardiovascular and thermal strain while completing arduous work in a hot environment despite fairly high chest skin temperatures. The total energy expenditure in the current study suggests job demands are similar to those of 15 years ago, while the increased water turnover may reflect a change in drinking habits.

Original languageEnglish
Article number576
Pages (from-to)221-226
Number of pages6
JournalWilderness and Environmental Medicine
Issue number2
StatePublished - Jun 1 2015


Disclaimer: The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Office of Naval Research or the Department of Defense. The investigators have conducted the research in adherence with the provisions of 32 CFR Part 219. Citations of commercial organizations and trade names in this report do not constitute an official Office of Naval Research endorsement or approval of the products or services of these organizations. The current project was funded by the Office of Naval Research, Grant Award N000140910850. The authors report no conflicts of interest.

FundersFunder number
Office of Naval ResearchN000140910850


    • Key words skin temperature
    • core temperature
    • field study
    • occupational physiology


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