Physiological And Thermal Strain Of Wildland Firefighters

Wildfire firefighting is extremely demanding occupation that mainly takes place during the summer season when forest conditions are more dry. The high physical demands of wildland firefighters come not only from the nature of the activities that need to be performed but also from the environmental conditions in which they are performed. PURPOSE: The aim of this study was to analyze the physiological demands and thermal strain of wildland firefighters during real wildfire suppression according to the firefighting tactics used. METHODS: Sixty wildland firefighters (28 ± 1 yr, 54.2 ± 1.1 ml·kg-1·min-1) volunteered and took part in this study. Wildfires (n = 152) were classified into three categories according to the kind of work performed: working near the flames (direct), working >100 m from the flames (indirect) or mixed. Heart rate (HR) and core temperature (CT) were measured during wildfire suppression. HR recordings were normalized into a training impulse (TRIMP) score, summating the intensity and duration of each wildfire. Moreover, the physiological strain index (PSI) and cumulative heat strain index (CHSI) were calculated using the HR and core temperature. RESULTS: Significantly higher (P < 0.05) HR and TRIMP·h-1 were found in direct (128 ± 2 bpm and 84.6 ± 1.9 units) and mixed (126 ± 2 bpm and 85.4 ± 1.8 units) attacks than in indirect attack (111 ± 3 bpm and 68.2 ± 1.8 units). The highest PSI (5.5 ± 0.8 units) and CHSI (3133 ± 362 units) were observed in the direct attack. Core temperature was not affected by wildfire attack tactics (38.0 ± 0.2). CONCLUSION: The present study showed the high workload sustained by wildland firefighters in the course of their work and that exercise and thermal strain during wildfire suppression are related to the kind of work performed.