title: Older firefighters are susceptible to age-related impairments in heat dissipation.
abstract: OBJECTIVE
  The aging-induced reduction in whole-body heat loss (HL) capacity generates concerns regarding the continued participation of older workers in occupations such as firefighting. We compared HL and change in body heat storage (S) during intermittent exercise in warm/dry and warm/humid conditions among older male firefighters (OLDER, n = 9, age = 54.7 ± 2.1 yr), older (age-matched) nonfirefighters (NON-FF, n = 9, age = 52.8 ± 1.2 yr), and young firefighters (YOUNG, n = 6, age = 26.7 ± 0.8 yr).
  
  
  METHODS
  We measured evaporative heat loss and dry heat exchange via the Snellen whole-body direct calorimeter while participants performed four 15-min bouts of cycling at 400 W of metabolic heat production separated by 15-min recovery periods in warm/dry (35 °C, 20% relative humidity) and warm/humid (35 °C, 60% relative humidity) conditions.
  
  
  RESULTS
  We found no differences (P > 0.05) in HL or cumulative S (ΔS) between OLDER and NON-FF in the warm/dry (ΔS: OLDER = 233 ± 26 kJ, NON-FF = 270 ± 29 kJ) or warm/humid (ΔS: OLDER = 548 ± 24 kJ, NON-FF = 504 ± 47 kJ) conditions. The OLDER and NON-FF had lower HL than the YOUNG during exercise in both environmental conditions (P < 0.05). The OLDER stored 40% (P > 0.05) and 46% (P = 0.004) more heat than YOUNG in the warm/dry and warm/humid conditions, respectively. The NON-FF stored 63% (P = 0.016) and 34% (P = 0.025) more heat than the YOUNG in the dry and humid conditions, respectively.
  
  
  CONCLUSIONS
  Older firefighters and age-matched nonfirefighters demonstrate similar HL and S during work in the heat. Moreover, HL is significantly reduced in older compared to younger firefighters during exercise in both warm/dry and warm/humid conditions. Consequently, older firefighters may be more susceptible to thermal injury while on duty than their younger counterparts.
authors.affiliation: 1Human Environmental Physiological Research Unit, University of Ottawa, Ontario, CANADA; 2Faculty of Physical Education and Sports, University of Sherbrooke, Sherbrooke, Quebec, CANADA; 3Departments of Medicine, Cardiac Sciences and Community Health Sciences, Faculties of Medicine and Kinesiology, University of Calgary, Calgary, Alberta, CANADA; and 4FAME Laboratory, Department of Exercise Science, University of Thessaly, Trikala, GREECE.
authors.forename: Glen P
authors.initials: GP
authors.lastname: Kenny
authors.forename: Joanie
authors.initials: J
authors.lastname: Larose
authors.forename: Heather E
authors.initials: HE
authors.lastname: Wright-Beatty
authors.forename: Pierre
authors.initials: P
authors.lastname: Boulay
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Sigal
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Flouris
mesh_terms: D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology*; D002151:Calorimetry / Q000379:methods; D005080:Exercise Test; D061388:Firefighters; D006801:Humans; D008297:Male; D008875:Middle Aged