Physiological Responses to Firefighting in Extreme Temperatures Do Not Compare to Firefighting in Temperate Conditions

Abstract

Purpose: The aim of this study was to examine physiological responses to two different simulated firefighting exercises: a firefighting exercise with flashovers, smoke, poor visibility and extreme temperatures (300°) in a burning container and a standard firefighting exercise in temperate conditions. Furthermore, a second purpose of the study was to find out if the contribution of strength and endurance capacities to firefighting performance changes when the demands of the firefighting exercise change.Methods: Sixteen professional firefighters performed a maximum treadmill test, strength testing, a standard simulated firefighting exercise (SFE) without heat and flashovers and a firefighting exercise with a simulation of the flashover phenomenon in a burning container (FOT). The treadmill testing was used to determine peak oxygen uptake (VO2peak), ventilatory threshold (VT1) and respiratory compensation point (RCP). Three intensity zones were identified according to heart rate (HR) values corresponding to VT1 and RCP: zone 1–HR below VT1, zone 2-HR between VT1 and RCP, zone 3–HR above RCP. Firefighting performance was determined by a simple time-strain-air depletion model (TSA) taking the sum of z-transformed parameters of time to finish the exercise, strain in terms of mean heart rate, and air depletion from the breathing apparatus. Correlations were then established between TSA based firefighting performance parameters and fitness variables representing strength and endurance.Results: HR was significantly lower during SFE (79.9 ± 6.9%HRmax) compared to FOT (85.4 ± 5.2%HRmax). During SFE subjects spent 24.6 ± 30.2% of time in zone 1, 65.8 ± 28.1% in zone 2 and 9.7 ± 16.6% in zone 3. During FOT subjects spent 16.3 ± 12.8% in zone 1, 50.4 ± 13.2% in zone 2 and 33.3 ± 16.6% in zone 3. Out of all correlations, relative VO2peak showed the highest relation to mean HR during SFE (−0.593) as well as FOT (−0.693).Conclusions: Endurance in terms of VO2peak is an important prerequisite for both firefighting exercises. However, for standard simulated firefighting exercises it is important to work below VT1. For firefighting exercises in extreme temperatures with smoke, poor visibility and unexpected flashovers a high fitness level is required in order to keep the time spent above RCP as short as possible.

Physical and Physiological Performance Determinants of a Firefighting Simulation Test

“…The best combination of predictors in this sample of German firefighters were absolute VO 2 max, low average breathing rate and time spent below ventilatory threshold. This, in combination with work combining environmental factors30 ,highlight further potential limiters to firefighting performance as a product of work tolerance and work efficiency.In both this setting and that of the current study, z-scores alone contain a sample bias where performance scores are relative to the sample mean and distribution, and should not be extrapolated to the larger population without caution. While we applied similar statistical analyses to the above, reproduction of this type of aggregateperformance score from individual z-scoresmay reduce this bias and be a more occupationally relevant way of understanding the necessary attributes for safe and effective firefighting in larger populations, including the UK.Practical relevanceThe current study was primarily designed to focus on the protocols and tests currentlyused by the UK Fire & Rescue Service.…”

The Validity and Reliability of a Treadmill Test for Structural Firefighter Applicants

“…For both treadmill test outcomes described above (average V˙O2 and V˙O2peak), we compared the mean values from the sample of 260 test records from our laboratory to the mean values reported by the other authorities. Confidence intervals (95%) were calculated for our data (n = 260) and the data from other sources (n = 12 studies for average V˙O2, 3,5,7,9,11–17 and n = 8 for recommended V˙O2peak 3–10 ) .…”

“…For more than four decades, researchers have worked to document the energy costs of structural firefighting and associated rescue work 1,2 . A fundamental reason for this effort has been to provide scientific evidence to justify cardiorespiratory endurance standards for firefighters (also described by others as cardiovascular fitness or aerobic fitness standards) 3–10 . Oxygen uptake (V˙O2) has usually been the criterion variable of interest measured during simulated fire-rescue work to quantify cardiorespiratory demand 3–17 .…”

“…Measuring the average rate of oxygen uptake during simulated fire-rescue work provides an accurate estimate of the aerobic energy cost of safe and effective work. In turn, physiological aptitude tests, which incorporate the correct type, intensity and duration of exercise, can be used to evaluate the cardiorespiratory endurance of firefighters against valid standards 2–11,14 . It should be noted that while cardiorespiratory endurance is recognized as an important aspect of physiological readiness for firefighting, this component alone cannot properly evaluate the complex interaction of aerobic, anaerobic, and strength physiology required for fire-fighting.…”

“…Early approaches to documenting aerobic demand 4,19 were limited to measuring the oxygen uptake during single tasks using the Douglas Bag method. Advancements in ambulatory spirometry instrumentation allowed measurement during scenarios that more accurately replicated the typical combination of activities during initial attack responses of structural firefighting (eg lifting, carrying, climbing, striking, dragging) 5–7,9–17 . Review of the relevant literature reveals that fire-rescue work requires relatively high rates of oxygen uptake (up to 3 L·min –1 ) for relatively short periods of time (typically up to approximately 2° min) 1,2 .…”