"Awake, smoky, and hot": providing an evidence-base for managing the risks associated with occupational stressors encountered by wildland firefighters.

To curtail the spread of wildfire, firefighters are often required to work long hours in hot, smoky conditions with little rest between consecutive shifts. In isolation, heat, smoke, and sleep disruption can have a detrimental impact on cognitive and physical abilities. Far less is known, however, about the combined impact that heat, smoke, and sleep disruption can have on firefighters' performance during wildfire suppression or on human performance in general. The available literature, though scant, suggests that audio and visual tracking may be degraded after sustained heat exposure following one night of sleep deprivation. Exposure to heat and carbon monoxide, in contrast, appears to have only limited impact on cognitive performance, even after physical exercise. Heat and carbon monoxide exposure does, however, increase physiological exertion to a given work or exercise bout. To the authors' knowledge, there are no published studies that have explored the impacts of heat exposure following sleep disruption on physical work performance, sleep disruption and smoke exposure on physical or cognitive work, or the combined impacts of sleep disruption, smoke and heat exposure on cognitive or physical work. While more integrative research is needed, the current review provides a summary of the available evidence and an indication of the degree of confidence agencies can have in the research. This will allow both the scientific community and agencies to make informed recommendations regarding the management of wildland firefighters' health and safety on the fireground.

Pack hike test finishing time for Australian firefighters: pass rates and correlates of performance.

The pack hike test (PHT, 4.83 km hike wearing a 20.4-kg load) was devised to determine the job readiness of USA wildland firefighters. This study measured PHT performance in a sample of Australian firefighters who currently perform the PHT (career land management firefighters, LMFF) and those who do not (suburban/regional volunteer firefighters, VFF). The study also investigated the relationships between firefighters' PHT performance and their performance across a range of fitness tests for both groups. Twenty LMFF and eighteen age-, body mass-, and height-matched VFF attempted the PHT, and a series of muscular endurance, power, strength and cardiorespiratory fitness tests. Bivariate correlations between the participants' PHT finishing time and their performance in a suite of different fitness tests were determined using Pearson's product moment correlation coefficient. The mean PHT finishing time for LMFF (42.2 ± 2.8 min) was 9 ± 14% faster (p = 0.001) than for VFF (46.1 ± 3.6 min). The pass rate (the percentage of participants who completed the PHT in under 45 min) for LMFF (90%) was greater than that of VFF (39%, p = 0.001). For LMFF, VO(2peak) in L min(-1)(r = -0.66, p = 0.001) and the duration they could sustain a grip 'force' of 25 kg (r = -0.69, p = 0.001) were strongly correlated with PHT finishing time. For VFF, VO(2peak) in mL kg(-1) min(-1)(r = -0.75, p = 0.002) and the duration they could hold a 1.2-m bar attached to 45.5 kg in a 'hose spray position' (r = -0.69, p = 0.004) were strongly correlated with PHT finishing time. This study shows that PHT fitness-screening could severely limit the number of VFF eligible for duty, compromising workforce numbers and highlights the need for specific and valid firefighter fitness standards. The results also demonstrate the strong relationships between PHT performance and firefighters' cardiorespiratory fitness and local muscular endurance. Those preparing for the PHT should focus their training on these fitness components in the weeks and months prior to undertaking the PHT.

Estimating the total energy demand for supra-maximal exercise using the VO2-power regression from an incremental exercise test.

The VO2-power regression and estimated total energy demand for a 6-minute supra-maximal exercise test was predicted from a continuous incremental exercise test. Sub-maximal VO2-power co-ordinates were established from the last 40 seconds (s) of 150-second exercise stages. The precision of the estimated total energy demand was determined using the 95% confidence interval (95% CI) of the estimated total energy demand. The linearity of the individual VO2-power regression equations was determined using Pearson's correlation coefficient. The mean 95% CI of the estimated total energy demand was 5.9 +/- 2.5 mL O2 Eq x kg(-1) x min(-1), and the mean correlation coefficient was 0.9942 +/- 0.0042. The current study contends that the sub-maximal VO2-power co-ordinates from a continuous incremental exercise test can be used to estimate supra-maximal energy demand without compromising the precision of the accumulated oxygen deficit (AOD) method.

The influence of pacing during 6-minute supra-maximal cycle ergometer performance.

The aim of this study was to evaluate the influence of pacing on performance, oxygen uptake (VO2), oxygen deficit and blood lactate accumulation during a 6-minute cycle ergometer test. Six recreational cyclists completed three 6-minute cycling tests using fast-start, even-pacing and slow-fast pacing conditions. Cycle ergometer performance was measured as the mean power output produced for each cycling test. Energy system contribution during each cycling trial was estimated using a modified accumulated oxygen deficit (AOD) method. Blood lactate concentration was analysed from blood sampled using a catheter in a forearm vein prior to exercise, at 2 minutes, 4 minutes and 6 minutes during exercise, and at 2 minutes, 5 minutes and 10 minutes post-exercise. There was no significant difference between the pacing conditions for mean power output (P = 0.09), peak VO2 (P = 0.92), total VO2 (P = 0.76), AOD (P = 0.91), the time-course of VO2 (P = 0.22) or blood lactate accumulation (P= 0.07). There was, however, a significant difference between the three pacing conditions in the oxygen deficit measured over time (P = 0.02). These changes in the time-course of oxygen deficit during cycling trials did not, however, significantly affect the mean power output produced by each pacing condition.