Inflammatory responses of older firefighters to intermittent exercise in the heat

Eur J Appl Physiol. 2014 Jun;114(6):1163-74. doi: 10.1007/s00421-014-2843-8. Epub 2014 Feb 23.


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 VO(2peak), 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 (T(re)) 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 T(re), 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Body Temperature
  • C-Reactive Protein / metabolism
  • Case-Control Studies
  • Exercise*
  • Firefighters*
  • Heart Rate
  • Heat-Shock Response*
  • Hot Temperature*
  • Humans
  • Inflammation / blood
  • Interleukin-6 / blood
  • Male
  • Middle Aged
  • Platelet Count
  • Thermogenesis
  • Tumor Necrosis Factor-alpha / blood


  • Interleukin-6
  • Tumor Necrosis Factor-alpha
  • C-Reactive Protein