title: Work patterns dictate energy demands and thermal strain during wildland firefighting.
abstract: 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.
authors.affiliation: Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, Missoula, MT.
authors.forename: John S
authors.initials: JS
authors.lastname: Cuddy
authors.affiliation: Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, Missoula, MT.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Sol
authors.affiliation: Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, Missoula, MT.
authors.forename: Walter S
authors.initials: WS
authors.lastname: Hailes
authors.affiliation: Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, Missoula, MT. Electronic address: brent.ruby@mso.umt.edu.
authors.forename: Brent C
authors.initials: BC
authors.lastname: Ruby
mesh_terms: D000328:Adult; D001831:Body Temperature; D001835:Body Weight; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D061388:Firefighters; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D008297:Male; D016273:Occupational Exposure; D005082:Physical Exertion / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology; D055814:Wilderness; D055815:Young Adult
keywords: core temperature; field study; occupational physiology; skin temperature