Physical and thermal strain of firefighters according to the firefighting tactics used to suppress wildfires

Abstract

The aim of this study was to analyse the physiological strain of firefighters, using heart rate (HR) and core temperature, during real wildfire suppression according to the type of attack performed (direct, indirect or mixed). Threeintensity zones were established according to the HR corresponding to the ventilatory threshold (VT) and respiratory compensation threshold (RCT): zone 1, <VT; zone 2 (Z2), between VT and RCT; zone 3 (Z3), >RCT. The exercise workload (training impulse (TRIMP)), the physiological strain index (PSI) and the cumulative heat strain index(CHSI) were calculated using the time spent in each zone, and the HR and core temperature, respectively. Significantly higher mean HR, time spent in Z2 and Z3 and TRIMP h⁻¹ were found in direct and mixed versus indirect attacks. The highest PSI and CHSI were observed in the direct attack. In conclusion, exercise strain and combined thermal strain, but not core temperature during wildfire suppression, are related to the type of attack performed.

Statement of relevance: Our findings demonstrated that wildfire firefighting is associated with high physiological demands, which vary significantly depending on the tactics chosen for performing the task. These results should be kept in mind when planning programmes to improve wildland firefighters' physical fitness, which will allow improvement in their performance.

Keywords:

• wildland firefighter
• wildfire
• heart rate
• core temperature
• exercise workload

Acknowledgements

This work has been funded by Empresa de Transformación Agraria, S.A. (TRAGSA), Mutua Fraternidad–Muprespa and Empresa de Gestión Medioambiental, S.A. (EGMASA). This study was conducted with the collaboration of the Área de Defensa contra Incendios Forestales, Dirección General de Medio Natural y Política Forestal, Ministerio de Medio Ambiente y Medio Rural y Marino, Spain.