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Inflammatory responses of older Firefighters to intermittent exercise in the heat

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Abstract

Purpose

Repeated strenuous work in the heat may predispose firefighters to augmented immune responses and inflammation. This study examined the immune responses in 12 older Firefighters (FF) and 12 older Non-Firefighters (Non-FF), and a group of 6 young FF and 6 young Non-FF, following intermittent exercise in the heat.

Methods

The participants, matched for age, body surface area, body composition, and VO2peak, cycled 4 × 15 min at moderate-to-high heat production (400 W), each followed by 15-min rest, in dry [10–20 % relative humidity (RH)] and humid (60 % RH) heat (35 °C). Rectal temperature (Tre) and heart rate (HR) were measured continuously, and blood samples at baseline (PRE) and following 60-min recovery (POST) were analyzed for Interleukin (IL)-6, Tumor Necrosis Factor (TNF-α), C-reactive protein (CRP), platelet count (PLT), and mean platelet volume (MPV).

Results

No differences were observed for Tre, HR, TNF-α, CRP, or PLT between the FF and Non-FF in either condition. The Non-FF had greater changes in IL-6 (Warm/Dry = +1.10 ± 0.18, Warm/Humid = +2.94 ± 0.74 pg mL−1), compared to the FF (Warm/Dry = +0.67 ± 0.17, Warm/Humid = +0.70 ± 0.33 pg mL−1), and MPV at PRE/POST compared to the FF. Between the young and older FF and Non-FF, no differences in T re, HR, PLT, or MPV were observed, however, elevated CRP (Warm/Dry) in the older FF, and IL-6 (Warm/Dry) and TNF-α (both conditions) in the older Non-FF, were observed.

Conclusions

The elevated IL-6 in the Non-FF is potentially indicative of increased strain in the Non-FF and/or adaptive changes in the FF due to the occupational demands.

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Abbreviations

Non-FF:

Non-Firefighters

FF:

Firefighters

IL:

Interleukin

TNF:

Tumor necrosis factor

CRP:

C-reactive protein

T re :

Rectal temperature

HR:

Heart rate

RH:

Relative humidity

VO2peak :

Peak oxygen uptake

\( \dot{V} {\text {O}}_{2}\) :

Oxygen uptake

M:

Metabolic energy expenditure

RER:

Respiratory exchange ratio

ec :

Caloric equivalent of a liter of oxygen when carbohydrates are oxidized

ef :

Caloric equivalent of a liter of oxygen when fat is oxidized

BD:

Becton, Dickinson and Company

ANOVA:

Analysis of variance

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Acknowledgments

This project was funded by a research grant provided by the Workplace Safety and Insurance Board (Ontario) (funding received as part of a larger study examining the effects of heat exposure limits for older workers) and the Canada Foundation for Innovation-Leaders Opportunity Fund (grants held by Dr. Glen P. Kenny). The authors wish to acknowledge Drs. M.B. DuCharme, A.J. Seely, and J.E. Yardley as part of the grant writing team. Dr. Glen Kenny was supported by a University of Ottawa Research Chair Award. Dr. Heather Wright was supported by a MITACS-Accelerate Fellowship (Vale Ltd.). Dr. Ronald Sigal was supported by a Health Senior Scholar award from Alberta Innovates-Health Solutions. The authors wish to thank the participants for their time and effort, Dr. Scott Miller and the firefighter volunteers of the Ottawa Fire Services, and Dr. Francois Haman, University of Ottawa, for the use of his laboratory and analytical equipment.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical standard

This study was performed according to the ethical standards of the University of Ottawa Health Sciences and Science Research Ethics Board and complies with the current laws of Canada.

Author information

Authors and Affiliations

  1. Human and Environmental Physiology Research Unit, School of Human Kinetics 125 University Private, University of Ottawa, Montpetit Hall, Room 367, Ottawa, Ontario, K1N 6N5, Canada

    Heather E. Wright-Beatty, Joanie Larose & Glen P. Kenny

  2. TM McLellan Research Inc, Stouffville, Canada, L4A 8A7

    Tom M. McLellan

  3. Clinical Epidemiology Program, Ottawa Health Research Institute, Ottawa, K1Y 4E9, Canada

    Ronald J. Sigal

  4. Departments of Medicine, Cardiac Sciences, and Community Health Sciences, Faculties of Medicine and Kinesiology, University of Calgary, Calgary, T2N 1N4, Canada

    Ronald J. Sigal

  5. Faculty of Physical Education and Sports, University of Sherbrooke, Sherbrooke, J1K 2R1, Canada

    Pierre Boulay

Authors
  1. Heather E. Wright-Beatty
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  2. Tom M. McLellan
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  3. Joanie Larose
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  4. Ronald J. Sigal
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  5. Pierre Boulay
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  6. Glen P. Kenny
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Corresponding author

Correspondence to Glen P. Kenny.

Additional information

Communicated by Narihiko Kondo.

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Wright-Beatty, H.E., McLellan, T.M., Larose, J. et al. Inflammatory responses of older Firefighters to intermittent exercise in the heat. Eur J Appl Physiol 114, 1163–1174 (2014). https://doi.org/10.1007/s00421-014-2843-8

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  • DOI: https://doi.org/10.1007/s00421-014-2843-8

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