Cara Lord

Validating 'fit for duty' tests for Australian volunteer fire fighters suppressing bushfires.

INTRODUCTION This study compared fire fighters work-rates and performance between the Pack Hike Test (PHT), Field Walk Test (FWT) and critical bushfire suppression tasks. METHODS Nineteen volunteer fire fighters undertook the PHT, whilst a further 11 also performed the FWT. All 30 fire fighters completed four critical tasks. Physical, physiological and subjective ratings were measured during tasks and tests. RESULTS Peak and mean heart rate during the Hose Drag was lower than during the FWT. Mean velocities for the PHT and FWT were higher than in all tasks except Hose Drag. Finishing times in the PHT and FWT were strongly correlated with finishing times for three and four of the critical tasks. CONCLUSIONS The PHT and FWT may be valid fit for duty tests for Australian rural fire fighters though the clear differences between the tests and some tasks may prompt fire agencies to consider other tests that more accurately simulate bushfire suppression work.

Frequency, Intensity, Time And Type Of Tasks Performed During Wildfire Suppression

Objective: To quantify the frequency, intensity, duration, and type of tasks performed by Australian rural fire crews when suppressing wildfires. Methods: Twenty-eight Australian rural firefighters worked across four, six-hour shifts fighting to curtail the spread of wildfire. Each firefighter wore a heart rate monitor and personal global positioning system (GPS) unit and was followed by a researcher filming their work activity. Video footage of each firefighter was synchronized with their heart rate and GPS data to quantify the frequency, intensity and duration of individual fireground tasks. Fireground tasks were isolated using a previously conducted job task analysis. Results: Firefighters performed 32 distinct fireground tasks. Task frequencies ranged from once to 103 times per six-hour shift. Individual tasks lasted 4 ± 2 s to 461 ± 387 s, were performed at speeds ranging from 0.12 ± 0.08 m•s-1 to 0.79 ± 0.40 m•s-1 and elicited mean heart rates that ranged between 97 ± 16 beats•min-1 (55.7 ± 8.7 percentage of age-predicted maximum heart rate (HRmax)) and 157 ± 15 beats•min-1 (86.2 ± 10.8%HRmax). Conclusion: Fireground tasks were, generally speaking, shorter, slower, and elicited lower heart rates than equivalent tasks previously simulated and reported in the literature. The differences between naturally occurring and simulated tasks question the value of isolated task simulations for conducting physical demands analyses en-route to developing job-specific fitness tests.

Firefighter feedback during active cooling: A useful tool for heat stress management?

Monitoring an individuals thermic state in the workplace requires reliable feedback of their core temperature. However, core temperature measurement technology is expensive, invasive and often impractical in operational environments, warranting investigation of surrogate measures which could be used to predict core temperature. This study examines an alternative measure of an individuals thermic state, thermal sensation, which presents a more manageable and practical solution for Australian firefighters operating on the fireground. Across three environmental conditions (cold, warm, hot & humid), 49 Australian volunteer firefighters performed a 20-min fire suppression activity, immediately followed by 20 min of active cooling using hand and forearm immersion techniques. Core temperature (Tc) and thermal sensation (TS) were measured across the rehabilitation period at five minute intervals. Despite the decline in Tc and TS throughout the rehabilitation period, there was little similarity in the magnitude or rate of decline between each measure in any of the ambient conditions. Moderate to strong correlations existed between Tc and TS in the cool (0.41, p<0.05) and hot & humid (0.57, p<0.05) conditions, however this was resultant in strong correlation during the earlier stages of rehabilitation (first five minutes), which were not evident in the latter stages. Linear regression revealed TS to be a poor predictor of Tc in all conditions (SEE=0.45-0.54°C) with a strong trend for TS to over-predict Tc (77-80% of the time). There is minimal evidence to suggest that ratings of thermal sensation, which represent a psychophysical assessment of an individuals thermal comfort, are an accurate reflection of the response of an individuals core temperature. Ratings of thermal sensation can be highly variable amongst individuals, likely moderated by local skin temperature. In account of these findings, fire managers require a more reliable source of information to guide decisions of heat stress management.

Oxygen Uptake and Heart Rate during Simulated Wildfire Suppression Tasks Performed by Australian Rural Firefighters

Objective: Australian rural fire crews safeguard the nation against the annual devastation of wildfire. We have previously reported that experienced firefighters identified seven physically demanding tasks for Australian rural fire crews suppressing wildfires. These firefighters rated the operational importance, typical duration, core fitness components, and likely frequency of the seven tasks. The intensity of these duties remains unknown. The aim of this study was to quantify the oxygen uptake (VO2), heart rate (HR) and movement speed responses during simulations of these physically demanding wildfire suppression tasks. Method: Twenty six rural firefighters (20 men, six women) performed up to seven tasks, during which time their HR and movement speed were recorded. The VO2 for each task was also calculated from the analysis of expired air collected in Douglas bags. Firefighters’ HR and movement speed were measured using HR monitors and portable global positioning system units, respectively. Results: The hose work tasks elicited a VO2 of 21-27 mL·kg-1·min-1 and peak HR of 77-87% age-predicted maximal HR (HRmax). Hand tool tasks were accompanied by VO2 of 28-34 mL·kg-1·min-1 and peak HR of 85-95%HRmax. Firefighters’ movement speed spanned 0.2 ± 0.1 to 1.8 ± 0.2 m·s-1 across the seven tasks. The cardiovascular responses in the hand tool tasks were, in most cases, higher (P<0.05) than during those elicited by the hose work tasks. Conclusions: The cardiovascular responses elicited during simulations of physically demanding wildfire suppression approximated those reported for similar tasks in urban and forestry fire fighting jurisdictions. The findings may prompt Australian rural fire agencies to consider cardiovascular disease risk screening and physical selection testing to ensure that healthy and fit firefighters are deployed to the fire ground.

Muscle activation during the Pack Hike test and a critical wildfire fighting task

The aim of this study was to examine the muscle activation of six global muscles during the successful completion of the Pack Hike test (PHT) and compare this to muscle activations during a critical wildfire fighting task. In-field surface electromyography was recorded from eight male wildfire fighters during the PHT and the rakehoe task - a critical wildfire suppression activity. All participants successfully completed the PHT within the 45-min time limit. No significant changes in peak muscle activation levels as well as no significant shifts in median frequency in the six muscle analysed were recorded during the 4.83-km hike. Significantly different peak muscle activation levels were recorded in four of the six muscles tested when the PHT was compared to the rakehoe task. These results suggest the PHT should not be administered in isolation and other tests that specifically challenge upper body muscle endurance should be incorporated into a battery that accurately assesses the job-specific fitness of wildfire fighters.