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

Heat strain in professional firefighters: physiological responses to a simulated smoke dive in extremely hot environments and the subsequent recovery phase

Firefighters risk heat strain during occupational tasks when exposed to extremely hot environmental conditions and performing high-intensity work. Relevant training scenarios are therefore essential. This study investigated the effect of a single simulated smoke dive and the following recovery phase on physiological and perceptual responses. Nineteen professional male firefighters (43 ± 8 yr) performed a 2-min stair walk and a15-min simulated smoke dive in a two-floor heat chamber (110°C to 272°C) (HEAT), followed by a 5-min stair walk outside the heat chamber. Heart rate (HR), gastrointestinal temperature (Tgi) and skin temperatures were registered continuously during the test. The Tgi increased significantly from the start (37.5 ± 0.3°C) to the end of HEAT (38.4 ± 0.4°C) and further increased after the heat exposure (39.6 ± 0.5°C). The HR also increased significantly from the start (92 ± 14 bpm) to the end of HEAT (185 ± 13 bpm) and increased after the heat exposure to a maximum of 190 ± 13 bpm. The simulated smoke dive induced high physiological strain on the firefighters, and the increase in Tgi and HR after the hot exposure must be considered during live fire events when repeated smoke dives are required.

Occupational Injuries of Spanish Wildland Firefighters: A Descriptive Analysis

The work of wildland firefighters, especially of the so-called 'Brigadas de Refuerzo contra Incendios Forestales', is characterised by high physical demands and extreme operating conditions. These professionals face long workdays (12 h), walking with heavy loads (~25 kg), being exposed to high temperatures (>30 °C), and handling specialised tools in high-risk environments. This study aimed to describe the prevalence of occupational injuries among members of the 'Brigadas de Refuerzo contra Incendios Forestales' and its relationship to variables such as age and work experience. A total of 217 wildland firefighters (18 female and 199 male) correctly answered a questionnaire developed on an ad hoc basis to meet the study's objectives. A high prevalence of occupational injuries was observed among them (~76%). Age and work experience were shown to be significantly associated with injuries. Individuals over 35 years of age with more than 10 years' experience had a higher probability of injury (OR = 2.14, CI = 1.12-4.06 and OR = 2.46, CI = 1.30-4.67, respectively). Injuries occurred mainly during physical training (~46%), followed by preventive work (~33%) and forest fires (~20%). The most common injuries were tendonitis and muscle pain (~44% and ~21% respectively), followed by sprains (~21%). The results underline the need for physical activity programmes adapted to help wildland firefighters, especially older and more experienced individuals. The identification of risk factors such as age and work experience can contribute to the prevention and management of occupational injuries among this group of highly specialised forestry workers. Specific preventative measures during training are required to mitigate the risk of injury among these crews, who play a crucial role in protecting the environment and public safety.

The Effects of Protein and Carbohydrate Supplementation, with and without Creatine, on Occupational Performance in Firefighters

BACKGROUND

The purpose of this study was to assess the effects of protein and carbohydrate supplementation, with and without creatine, on occupational performance in firefighters.

METHODS

Using a randomized, double-blind approach, thirty male firefighters (age: 34.4 ± 8.4 yrs., height: 1.82 ± 0.07 m; weight: 88.6 ± 12.5 kg; BF%: 17.2 ± 5.8%) were randomized to receive either (A.) 25 g of whey protein isolate + 25 g of carbohydrate powder (ProCarb group); or (B.) ProCarb + 5 g of creatine (Creatine group) in a double-blind fashion over a period of 21-26 days (depending on shift rotations) to evaluate the impact of supplementation on occupation-specific performance. At baseline and following supplementation, firefighters completed a battery of tests. These tests included an aerobic speed test on an air-braked cycle ergometer followed by the hose carry, body drag, stair climb, and Keiser sled hammer for time.

RESULTS

No significant differences in measures of performance were observed at baseline (p > 0.05). There was a significant main effect for time observed for rescue, stair climb, total time to completion, and time trial performance (p < 0.05). There was a significant group × time (p < 0.05) interaction for rescue and forcible entry. Independent sample t-tests indicated that the Creatine group experienced a greater reduction (from baseline) in completion time for the rescue (1.78 ± 0.57 s, 95% CI: 0.61, 2.95 s, p = 0.004) and forcible entry (2.66 ± 0.97 s, 95% CI: 0.68, 4.65 s, p = 0.01) tests compared to the ProCarb group. No significant group × time interactions were observed for the hose line advance, stair climb, total time to completion, and time trial performance (p > 0.05).

CONCLUSIONS

The addition of supplemental creatine to a protein and carbohydrate supplement to the diet of career firefighters throughout a three week period improves occupational performance in firefighters in specific areas of high-intensity, repetitive actions.

Firefighter occupational factors and the risk of preterm birth: results from a survey of women firefighters in the USA

OBJECTIVES

Previous research has suggested that women firefighters may have a greater risk of adverse reproductive outcomes compared with non-firefighting women. In this study, we investigated the association between firefighter occupational factors and risk of preterm birth.

METHODS

This cross-sectional analysis of US firefighters surveyed in 2017 compared preterm birth among firefighters to non-firefighters using age-at-pregnancy-standardised prevalence ratios. Generalised estimating equations estimated relative risks and 95% CIs between firefighter occupational factors (career or volunteer, wildland status, shift schedule, fire responses, work restriction) and preterm birth risk. We adjusted for age-at-pregnancy, education, gravidity, BMI, and smoking and considered effect modification by age-at-pregnancy and career versus volunteer status.

RESULTS

Among 934 women who reported 1356 live births, 12% were preterm (n=161). Preterm birth prevalence among firefighters was 1.41 times greater than non-firefighters (95% CI 1.18 to 1.68). Among wildland and combination wildland/structural firefighters, volunteers had 2.82 times the risk of preterm birth (95% CI 1.19 to 6.67) compared with career firefighters. Firefighters who started restricting their work in the 2nd trimester had a nonsignificant 0.67 times lower risk of preterm birth than those who started in the 3rd trimester or did not restrict work at all (95% CI 0.43 to 1.03).

CONCLUSIONS

Firefighters may have greater risk of preterm birth than non-firefighters, which could be influenced by roles in the fire service and work restrictions taken.

Chronic Pain in Spanish Wildland Firefighters

The work performed by wildland firefighters (WFFs) is very demanding owing to the conditions in which they have to operate. It has been reported that these professionals walk long distances over unstable and steep terrain carrying heavy loads, handle tools manually and repeatedly and are subject to a high level of thermal stress. Under such conditions, the risk of developing chronic pain (CP) is high, although despite this, there are no available data pertaining to CP among WFFs, to the best of our knowledge. As such, the aim of this study is to describe CP in Spanish helitack crews, for which purpose 221 WFFs (203 men and 18 women) completed an online self-report questionnaire. Approximately 60% of WFFs reported suffering from CP, of which 45.5% had CP in more than one body region at the same time. Age and length of service were associated with the probability of suffering from CP. Likewise, the age and height of WFFs and weight of the protective equipment used increased the prevalence of CP. Lastly, gender and job position affected CP location, with women and forepersons reporting greater prevalence of CP in the lower limbs. To conclude, the results obtained suggest the major prevalence of CP among Spanish WFFs, with current data suggesting in turn the importance that age, stature, gender, length of service, weight of protective equipment and job position have on the prevalence and location of CP.

Deterioration of Lipid Metabolism Despite Fitness Improvements in Wildland Firefighters

OBJECTIVE

Determine serum lipid and general health/fitness alterations following a 5-month wildfire suppression season.

METHODS

We recruited 100 wildland firefighters (WLFFs) to a 5-month pre- to post-season observational study. Nude body mass, blood pressure (BP), grip strength, and step-test heart rate (HR) were recorded. Blood samples were collected for lipid panel analysis (total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, triglycerides, triglyceride:HDL-cholesterol ratio). Two-tailed dependent t-tests determined statistical significance (p < 0.05).

RESULTS

There were pre- to post-season changes in nude body mass (+2 ± 4%, p = 0.001), systolic BP (-2 ± 10%, p = 0.01), step-test HR (-5 ± 10%, p < 0.001), and all serum lipids (total cholesterol: +5 ± 14%, p = 0.02, HDL-cholesterol: -1 ± 17%, p = 0.04, LDL-cholesterol: +8 ± 22%, p = 0.02, VLDL-cholesterol: +31 ± 49%, p < 0.001, triglycerides: +30 ± 49%, p < 0.001, triglyceride:HDL-cholesterol ratio: +37 ± 58%, p < 0.001). Pre- to post-season diastolic BP (p = 0.12) and grip strength (p = 0.60) remained stable.

CONCLUSIONS

WLFFs demonstrate maladaptive serum lipids and body mass alterations despite subtle aerobic fitness improvements.

Occupational factors and miscarriages in the US fire service: a cross-sectional analysis of women firefighters

BACKGROUND

Evidence from previous studies suggests that women firefighters have greater risk of some adverse reproductive outcomes. The purpose of this study was to investigate whether women firefighters had greater risk of miscarriage compared to non-firefighters and whether there were occupational factors associated with risk of miscarriage among firefighters.

METHODS

We studied pregnancies in the United States fire service using data from the Health and Wellness of Women Firefighters Study (n = 3181). We compared the prevalence of miscarriage among firefighters to published rates among non-firefighters using age-standardized prevalence ratios. We used generalized estimating equations to estimate relative risks (RRs) and 95% confidence intervals (CIs) between occupational factors (employment (career/volunteer), wildland firefighter status (wildland or wildland-urban-interface/structural), shift schedule, fire/rescue calls at pregnancy start) and risk of miscarriage, adjusted for age at pregnancy, education, gravidity, BMI, and smoking. We evaluated if associations varied by age at pregnancy or employment.

RESULTS

Among 1074 firefighters and 1864 total pregnancies, 404 pregnancies resulted in miscarriages (22%). Among most recent pregnancies, 138 resulted in miscarriage (13%). Compared to a study of US nurses, firefighters had 2.33 times greater age-standardized prevalence of miscarriage (95% CI 1.96-2.75). Overall, we observed that volunteer firefighters had an increased risk of miscarriage which varied by wildland status (interaction p-value< 0.01). Among structural firefighters, volunteer firefighters had 1.42 times the risk of miscarriage (95% CI 1.11-1.80) compared to career firefighters. Among wildland/wildland-urban-interface firefighters, volunteer firefighters had 2.53 times the risk of miscarriage (95% CI 1.35-4.78) compared to career firefighters.

CONCLUSIONS

Age-standardized miscarriage prevalence among firefighters may be greater than non-firefighters and there may be variation in risk of miscarriage by fire service role. Further research is needed to clarify these associations to inform policy and decision-making.

Preventing and Monitoring Work-Related Diseases in Firefighters: A Literature Review on Sensor-Based Systems and Future Perspectives in Robotic Devices

In recent years, the necessity to prevent work-related diseases has led to the use of sensor-based systems to measure important features during working activities. This topic achieved great popularity especially in hazardous and demanding activities such as those required of firefighters. Among feasible sensor systems, wearable sensors revealed their advantages in terms of possibility to conduct measures in real conditions and without influencing the movements of workers. In addition, the advent of robotics can be also exploited in order to reduce work-related disorders. The present literature review aims at providing an overview of sensor-based systems used to monitor physiological and physical parameters in firefighters during real activities, as well as to offer ideas for understanding the potentialities of exoskeletons and assistive devices.

Carbohydrate ingestion attenuates cognitive dysfunction following long-duration exercise in the heat in humans

INTRODUCTION

To determine if electrolyte or carbohydrate supplementation vs. water would limit the magnitude of dehydration and decline in cognitive function in humans following long-duration hyperthermic-exercise.

METHODS

24 subjects performed 3 visits of 2 h walking (3mph/7% grade) in an environmental chamber (33 °C/10% relative humidity). In random order, subjects consumed water (W), electrolytes (Gatorade Zero; E), or electrolytes+carbohydrates (Gatorade; E+C). Throughout exercise (EX), subjects carried a 23 kg pack and drank ad-libitum. Pre-and post-EX, body mass (BM) and plasma osmolality (pOsm) were measured. Physiological Strain Index (PSI) and core temperature (T_C) were recorded every 15 min. Plasma glucose (GLU) was measured every 30 min. Cognitive processing (SCWT) was measured post-EX and compared to baseline (BL). A subset of 8 subjects performed a normothermic (N) protocol (21 °C/ambient humidity) to ascertain how the exercise stimulus influenced hydration status and cognition without heat.

RESULTS

There were no significant differences between fluid conditions (W, E, E+C) for BM loss (Δ2.5 ± 0.2, 2.5 ± 0.2, 2.3 ± 0.2 kg), fluid consumption (1.9 ± 0.2, 1.9 ± 0.2, 1.8 ± 0.2L), pOsm (Δ1.5 ± 2.7, 2.2 ± 2.4, 2.0 ± 1.5 mmol/L), peak-PSI (7.5 ± 0.4, 7.0 ± 0.6, 7.9 ± 0.5), and peak-T_C (38.7 ± 0.1, 38.6 ± 0.2, 38.8 ± 0.2 °C). GLU decreased significantly in W and E, whereas it increased above BL in E+C at 60, 90, and 120 min (P < 0.05). Compared to BL values (43.6 ± 26 ms), SCWT performance significantly decreased in all conditions (463 ± 93, 422 ± 83, 140 ± 52 ms, P < 0.05). Importantly, compared to W and E, the impairment in SCWT was significantly attenuated in E+C (P < 0.05). As expected, when compared to the heat-stress protocol (W, E, E+C), N resulted in lower BM loss, fluid consumption, and peak-PSI (1.1 ± 0.1 kg, 1.2 ± 0.7L, 4.8, respectively), and improved SCWT performance.

CONCLUSIONS

These data are the first to suggest that, independent of supplementation variety, cognitive processing significantly decreases immediately following long-duration exercise in the heat in healthy humans. Compared to water and fluids supplemented with only electrolytes, fluids supplemented with carbohydrates significantly blunts this decrease in cognitive function.

Evaluation of Environmental Conditions on Self-Selected Work and Heat Stress in Wildland Firefighting

INTRODUCTION

The purpose of this study was to evaluate heat stress occurring in wildfire management activities with variable environmental conditions.

METHODS

Direct observation and real-time wireless physiological monitoring allowed for weather and physiological metrics, including heart rate, core temperature (T_c), skin temperature, and physiological strain index (PSI), of male (n=193) and female (n=28) wildland firefighters (WLFFs) to be recorded during wildfire management activities. Accelerometry data were used to categorize intensity level of activity.

RESULTS

Ambient temperature and relative humidity values were used to compute the heat index (HI; n=3891 h) and divided into quartiles (Q1: 13.3-25.1°C; Q2: 25.2-26.4°C; Q3: 26.5-28.9°C; Q4: 29.0-49.1°C). Activity levels remained relatively constant across all HI quartiles. The percentage of time spent performing moderate/vigorous activities was lowest during the hotter Q4 (Q1: 3%; Q2: 2%; Q3: 2%; Q4: 1%). Heart rate, T_c, PSI, and skin temperature associations with HI varied by resource type. Sixty-one percent of WLFFs (n=134) experienced a T_c ≥38.0°C, and 50% of WLFFs (n=111) experienced a PSI ≥6.0.

CONCLUSIONS

Heat stress was prevalent as WLFFs performed job tasks of varying intensities in all ambient conditions. Spontaneous bouts of arduous labor, duration of work shifts, and other occupation characteristics present the possibility for substantial durations of hyperthermia, although no heat-related injuries occurred in this study. Despite chronic exposure to rugged sloped terrain, load carriage, and environmental conditions, self-regulation and individual attention to managing work:rest appears to be the primary management strategy in mitigating excessive accumulation of body heat in this occupation.

Influence of Personal Protective Equipment on Wildland Firefighters' Physiological Response and Performance during the Pack Test

The Pack Test (PT) is a widely used test to establish readiness for work in wildland firefighting. It is common to perform this test dressed in regular exercise clothing. However, wildland firefighters (WFF) have to wear personal protective equipment (PPE) during their deployments, which increases the physiological strain and reduces their work capacity. This study aimed to analyse the impact of full PPE on PT performance. Nine male professional WFF performed in random order a PT walking at the fastest possible self-pace wearing two different clothing configurations: (i) traditional short sports gear (SG) and (ii) the PPE currently used by Spanish WFF. Heart rate (HR), rating of perceived exertion and lap time were recorded during the PT. In addition, oxygen uptake (VO₂) was estimated through the individual VO₂–HR relationship previously obtained during a graded exercise test. There was a significant decrease in the PT performance (i.e., completion time) (~12%, p < 0.05) in PPE. The physiological demands with this configuration were significantly higher (~10%, p < 0.05). WFF spent ~13 min above the anaerobic threshold in PPE vs. ~4 min in SG. A multiple stepwise regression analysis revealed that PT performance variation might be explained by the maximal aerobic velocity (84.5%) in PPE and the VO_2max (75.9%) in SG. In conclusion, wearing complete PPE increases WFF’s physiological strain, which translates into a significant PT performance reduction. Performing the test walking at the fastest possible self-pace wearing the PPE would better reflect the high-intensity effort periods reported in real scenarios.

Self-selected fluid volume and flavor strength does not alter fluid intake, body mass loss, or physiological strain during moderate-intensity exercise in the heat

INTRODUCTION

The purpose of this study was to determine the effects of ad libitum flavor and fluid intake on changes in body mass (BM) and physiological strain during moderate intensity exercise in the heat.

METHODS

Ten subjects (24±3yrs, 7M/3F) performed 60 min of treadmill walking at 1.3 m/s and 7% grade in an environmental chamber set to 33 °C and 10% relative humidity while carrying a 22.7 kg pack on two different occasions. Subjects consumed either plain water or water plus flavor (Infuze), ad libitum, at each visit. Pre and post exercise, fluid consumption (change in fluid reservoir weight) and BM (nude) were measured. During exercise, heart rate (HR), systolic blood pressure (SBP), rate of perceived exertion (RPE), oxygen consumption (VO₂), respiratory exchange ratio (RER), core temperature (T_C), and physiological strain index (PSI) were recorded every 15 min during exercise.

RESULTS

No significant differences were observed for fluid consumption between fluid conditions (512 ± 97.2 mL water vs. 414.3 ± 62.5 mL Infuze). Despite a significant decrease from baseline, there were no significant differences in overall change of BM (Δ -1.18 vs. -0.64 Kg) or percent body weight loss for water and Infuze conditions, respectively (1.58 ± 0.6 and 0.79 ± 0.2%). Furthermore, there were no significant differences in HR (144 ± 6 vs. 143 ± 8 bpm), SBP (157 ± 5 vs. 155 ± 5 mmHg), RPE, VO₂ (27.4 ± 0.9 vs. 28.1 ± 1.2 ml/Kg/min), RER, T_C (38.1 ± 0.1 vs. 37.0 ± 0.1 °C), and peak PSI (5.4 ± 0.4 vs. 5.7 ± 0.8) between conditions.

CONCLUSIONS

Offering individuals the choice to actively manipulate flavor strength did not significantly influence ad libitum fluid consumption, fluid loss, or physiological strain during 60 min of moderate intensity exercise in the heat.

Risk for heat-related illness among wildland firefighters: job tasks and core body temperature change

Objectives

In order to make recommendations to protect wildland firefighters (WLFFs) from heat-related illness, the role physical exertion plays on core body temperature (Tc) in the work environment needs to be considered. We aimed to estimate the association of time-varying job tasks with differing exertion levels on change in Tc, among WLFFs engaged in fire management activities, while controlling for ambient conditions and individual characteristics. In addition, we examined whether duration of tasks modified the relationship between task and change in Tc.

Methods

We used data from The Wildland Firefighter Heat Related Illness study, a repeated measures study with individual-level data on 301 WLFFs from 2013 to 2016. Job tasks over one full shift were recorded and categorised into four levels (sedentary, light, moderate and high) based on estimated exertion levels. Tc was measured every 15 s using an ingestible sensor and personal monitors measured ambient conditions. The analysis used generalised estimating equations with an autoregressive correlation structure.

Results

We found statistically significant associations between job tasks with increased physical demand and increases in Tc. When compared with sedentary tasks, the estimated increases in Tc for light, moderate and high activity tasks of average duration were 0.07°C (95% CI 0.02 to 0.11°C), 0.19°C (95% CI 0.15 to 0.23) and 0.44°C (95% CI 0.39 to 0.49°C), respectively. In addition, we found evidence of interaction between task type and duration.

Conclusions

This study supports the hypothesis that occupational exposure to physical exertion increases Tc, highlighting the need to update recommendations to protect WLFFs from heat-related illness.

Indices of physiological strain for firefighters of the Australian Defence Forces

High levels of exertion and physiological strain are the leading cause of fireground injuries. The Physiological Strain Index (PSI) provides a rating of strain based on body core temperature and heart rate; however, it may underestimate the strain of workers in protective clothing as skin temperature may be elevated. This study aimed to examine the relationship between the PSI and an Adaptive Physiological Strain Index (aPSI) that incorporates skin temperature, among firefighters wearing protective clothing. Nine male firefighters of the Australian Defence Force volunteered to participate. Participants conducted scenario-based activities while wearing turnout gear and breathing apparatus. Working in teams of four, participants would respond to a situation around and within a small building with several rooms that could be filled with smoke, however, no live fire was present. Heart rate, gastrointestinal temperature, and skin temperature were monitored throughout work and rehabilitation. Physiological strain was estimated via the PSI and aPSI. Absolute peak PSI and aPSI ratings were significantly different during work (PSI: 7.3 ± 1.6; aPSI 8.2 ± 2.0; p < 0.001). The aPSI produced higher ratings of physiological strain, >0.5 above PSI, progressively from a moderate level of strain (>6). The aPSI may provide a more accurate indication of a level of "maximal strain" for encapsulated workers than the original PSI, coincident with the occupational limits for body core temperature of 38.0 °C for general occupational groups, or 38.5 °C for selected and acclimatised personnel.

Characterizing Wildland Firefighters' Thermal Environment During Live-Fire Suppression

Wildland firefighters work under adverse environments (e.g., heat and fire exposure), which contribute to increasing the heat strain. Despite this there is a paucity of knowledge about the thermal environment in real wildfire suppression scenarios. Therefore, the main purpose of this study was to characterize the environmental thermal exposure and the risk of heat burn injuries during real wildfire suppression (n = 23). To characterize the wildland firefighter’s (n = 5) local thermal exposure, measurements of air temperature and heat flux were performed. Heat flux measurements were made using four thin-planar heat flux sensors. Two were affixed on the outer surface of the garment on the left chest and thigh. Two other sensors were placed on the inner surface of the fabric in parallel to those placed externally. Four thermal classes were defined based on the heat flux across the inner sensors (≤1000, ≤5000, ≤7000, and >7000 W⋅m^–2). The risk of pain and first-degree burns were calculated using the dose of thermal radiation method. The inner sensors mean and maximum heat flux and environment temperature were 286.7 ± 255.0 and 2370.4 ± 3004.5 W⋅m^–2 and 32.6 ± 8.9 and 78.0 ± 8.9°C, respectively. Approximately 81, 15, and 3.5% of the exposure time the heat flux was ≤1000, >1000–5000, and >5000 W⋅m^–2, respectively. The highest average and maximum thermal dose values were ∼94 and ∼110 (kW⋅m^–2)^4/3⋅s. In conclusion, the thermal exposure obtained may be considered light. However, high thermal exposure values may be obtained in punctual moments, which can elicit first-degree burns.

Postural stability pattern as an important safety factor of firefighters

BACKGROUND

Firefighting is a hazardous profession that involves high fall risk and is crucial component for the safety of people.

OBJECTIVE

The aim of this study was to identify factors that impact on postural stability patterns of firefighters.

METHODS

The study examined 177 Polish firefighters from the National Firefighting and Rescue System (NFRS) aged 31.9±10.1 years, with body height of 179.6±5.93, body mass of 83.9±11.0 and BMI of 26.0±3.03. Postural stability was evaluated by means of the Balance System SD (Biodex USA) set at the level 12 of instability, in a sportswear, bunker gear, with and without visual input. The fall risk test (FRI) was also performed. Four indices were analysed: overall stability index (OSI), anterior-posterior stability index (APSI), medial-lateral stability index (MLSI), and fall risk index (FRI).

RESULTS

Mean results for fall risk index (FRI) were in the normal range for all age groups regardless of the type of clothing the firefighters were wearing. Individual results obtained in the fall risk test, 128 firefighters were in the normal range for their age, furthermore, 10 firefighters obtained better results than the normal range, 34 firefighters had worse results and 5 people failed to complete the test. Postural stability with eyes closed was found to decline with age. Wearing bunker gear did not have an effect on postural stability.

CONCLUSIONS

Balance tests should be integrated into the firefighting training routines in order to improve balance and support fall prevention. Exercises with reduced visual input should also be incorporated into the training methodology.

Physical employment standard for Canadian wildland firefighters: examining test-retest reliability and the impact of familiarisation and physical fitness training

To assess the impact of repeat performances (familiarisation) plus exercise training on completion time for the Ontario Wildland Firefighter (WFF) Fitness Test circuit (WFX-FIT), normally active general population participants (n = 145) were familiarised to the protocol then randomised into (i) exercise training, (ii) circuit only weekly performances or (iii) controls. At Baseline, the WFX-FIT pass rate for all groups combined was 11% for females and 73% for males, indicating that the Ontario WFX-FIT standard had a possible adverse impact on females. Following test familiarisation, mean circuit completion times improved by 11.9% and 10.2% for females and males, respectively. There were significant improvements in completion time for females (19.8%) and males (16.9%) who trained, plus females (12.2%) and males (9.8%) who performed the circuit only, while control participants were unchanged. Post training, the pass rate of the training group was 80% for females and 100% for males. Practitioner Summary: This paper details the impact of familiarisation plus exercise training as accommodation to mitigate potential adverse impact on initial attack wildland firefighter test performance. The results underscore the importance of test familiarisation opportunities and physical fitness training programmes that are specific to the demands of the job.

Physical employment standard for Canadian wildland fire fighters; developing and validating the test protocol

Developing the Canadian initial attack (IA) wildland fire fighter (WFF) physical employment standard (WFX-FIT) began in a previous investigation with a physical demands analysis in which hand and back carrying a 28.5 kg pump, back carrying a 25 kg hose pack and advancing charged hose were identified as the critical IA emergency tasks. In the present study, a circuit was created incorporating simulations of the critical tasks with faster completion times required for provinces with more arduous terrains. The oxygen cost (mean ± SD VO₂ mL∙kg^-1∙min^-1) of performing IA WFF tasks sequentially on the job was 37 ± 6 compared to 37 ± 4 when performing the WFX-FIT, indicating strong construct validity. Content validation ratings comparing the likeness of on-the-job tasks to simulated tasks in the WFX-FIT provided strong agreement. These validations confirm that the physical demands involved in performing the WFX-FIT are the same as IA wildland fire fighting. Practitioner Summary: This paper details the process used to develop and validate the physical employment standard for jurisdictional employment and national exchange of IA WFF. The range of cut-scores reflects the differences in jurisdictional physical demands due to terrain difficulty, fire management policy on fire risk and forest value index.

On the use of wearable physiological monitors to assess heat strain during occupational heat stress

Workers in many industries are required to perform arduous work in high heat-stress conditions, which can lead to rapid increases in body temperature that elevate the risk of heat-related illness and even death. Traditionally, effort to mitigate work-related heat injury has been directed toward the assessment of environmental heat stress (e.g., wet-bulb globe temperature), rather than toward the associated physiological strain responses (e.g., heart rate and skin and core temperatures). However, because a worker’s physiological response to a given heat stress is modified independently by inter-individual factors (e.g., age, sex, chronic disease, others) and intra-individual factors both within (e.g., medication use, fitness, acclimation and hydration state, others) and beyond (e.g., shift duration, illness, others) the worker’s control, it becomes challenging to protect workers on an individual basis from heat-related injury without assessing those physiological responses. Recent advancements in wearable technology have made it possible to monitor one or more physiological indices of heat strain. Nonetheless, information on the utility of the wearable systems available for assessing occupational heat strain is unavailable. This communication is therefore directed toward identifying the physiological indices of heat strain that may be quantified in the workplace and evaluating the wearable monitoring systems available for assessing those responses. Finally, emphasis is placed on the barriers associated with implementing these devices to assist in mitigating work-related heat injury. This information is fundamental for protecting worker health and could also be utilized to prevent heat illnesses in vulnerable people during leisure or athletic activities.

The Effects of Simulated Wildland Firefighting Tasks on Core Temperature and Cognitive Function under Very Hot Conditions

Background: The severity of wildland fires is increasing due to continually hotter and drier summers. Firefighters are required to make life altering decisions on the fireground, which requires analytical thinking, problem solving, and situational awareness. This study aimed to determine the effects of very hot (45°C; HOT) conditions on cognitive function following periods of simulated wildfire suppression work when compared to a temperate environment (18°C; CON). Methods: Ten male volunteer firefighters intermittently performed a simulated fireground task for 3 h in both the CON and HOT environments, with cognitive function tests (paired associates learning and spatial span) assessed at baseline (cog 1) and during the final 20-min of each hour (cog 2, 3, and 4). Reaction time was also assessed at cog 1 and cog 4. Pre- and post- body mass were recorded, and core and skin temperature were measured continuously throughout the protocol. Results: There were no differences between the CON and HOT trials for any of the cognitive assessments, regardless of complexity. While core temperature reached 38.7°C in the HOT (compared to only 37.5°C in the CON; p < 0.01), core temperature declined during the cognitive assessments in both conditions (at a rate of -0.15 ± 0.20°C·hr-1 and -0.63 ± 0.12°C·hr-1 in the HOT and CON trial respectively). Firefighters also maintained their pre-exercise body mass in both conditions, indicating euhydration. Conclusions: It is likely that this maintenance of euhydration and the relative drop in core temperature experienced between physical work bouts was responsible for the preservation of firefighters' cognitive function in the present study.

Physiological and perceptual strain of firefighters during graded exercise to exhaustion at 40 and 10 °C

Purpose. To study whether perceptual identification should be included as a measure to evaluate physiological stress. Methods. Physiological variables oxygen uptake (V_O2), ventilation, heart rate, blood lactate concentration, rectal temperature (T_rec) and mean skin temperature, and perceptual variables rate of perceived exertion, thermal sensation and time to exhaustion, were measured at submaximal and maximal intensities during graded exercise on a treadmill to exhaustion in 12 firefighters wearing protective clothing and extra mass at 40 and 10 °C. Physiological strain index (PhSI) and perceptual strain index (PeSI) were calculated. Results. Apart from T_rec, all physiological and perceptual variables were higher at submaximal intensities of 40 °C. Time to exhaustion was 16% shorter and the corresponding V_O2 was reduced by 7% in the heat. A high correlation (r = 89) between PhSI and PeSI was found at both temperatures. PeSI scores were equal to PhSI at both ambient temperatures, except at the two highest intensities in the heat, where PeSI was higher. Conclusions. These findings support use of perceptual identification to evaluate physiological stress. However, at very high intensities under hot conditions the perceptual strain was estimated higher than the physiological strain. More precise indexes are needed to include perceptual measures in safety standard.

Relationships between strength and endurance parameters and air depletion rates in professional firefighters

The aim of this study was to quantify the physical demands of a simulated firefighting circuit and to establish the relationship between job performance and endurance and strength fitness measurements. On four separate days 41 professional firefighters (39 ± 9 yr, 179.6 ± 2.3 cm, 84.4 ± 9.2 kg, BMI 26.1 ± 2.8 kg/m2) performed treadmill testing, fitness testing (strength, balance and flexibility) and a simulated firefighting exercise. The firefighting exercise included ladder climbing (20 m), treadmill walking (200 m), pulling a wire rope hoist (15 times) and crawling an orientation section (50 m). Firefighting performance during the simulated exercise was evaluated 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. Multiple regression analysis based on the TSA-model served for the identification of the physiological determinants most relevant for professional firefighting. Three main factors with great influence on firefighting performance were identified (70.1% of total explained variance): VO2peak, the time firefighter exercised below their individual ventilatory threshold and mean breathing frequency. Based on the identified main factors influencing firefighting performance we recommend a periodic preventive health screening for incumbents to monitor peak VO2 and individual ventilatory threshold.

Novel Tools in Determining the Physiological Demands and Nutritional Practices of Ontario FireRangers during Fire Deployments

INTRODUCTION

The seasonal profession of wildland fire fighting in Canada requires individuals to work in harsh environmental conditions that are physically demanding. The purpose of this study was to use novel technologies to evaluate the physiological demands and nutritional practices of Canadian FireRangers during fire deployments.

METHODS

Participants (n = 21) from a northern Ontario Fire Base volunteered for this study and data collection occurred during the 2014 fire season and included Initial Attack (IA), Project Fire (P), and Fire Base (B) deployments. Deployment-specific energy demands and physiological responses were measured using heart-rate variability (HRV) monitoring devices (Zephyr BioHarness3 units). Food consumption behaviour and nutrient quantity and quality were captured using audio-video food logs on iPod Touches and analyzed by NutriBase Pro 11 software.

RESULTS

Insufficient kilocalories were consumed relative to expenditure for all deployment types. Average daily kilocalories consumed: IA: 3758 (80% consumption rate); P: 2945±888.8; B: 2433±570.8. Average daily kilocalorie expenditure: IA: 4538±106.3; P: 4012±1164.8; B: 2842±649.9. The Average Macronutrient Distribution Range (AMDR) for protein was acceptable: 22-25% (across deployment types). Whereas the AMDR for fat and carbohydrates were high: 40-50%; and low: 27-37% respectively, across deployment types.

CONCLUSIONS

This study is the first to use the described methodology to simultaneously evaluate energy expenditures and nutritional practices in an occupational setting. The results support the use of HRV monitoring and video-food capture, in occupational field settings, to assess job demands. FireRangers expended the most energy during IA, and the least during B deployments. These results indicate the need to develop strategies centered on maintaining physical fitness and improving food practices.

A cross-sectional survey of occupational history as a wildland firefighter and health

BACKGROUND

Little is known regarding the impact of long-term wildland firefighting on health. Our objective was to investigate associations between duration of wildland firefighting experience and the prevalence of self-reported health outcomes.

METHODS

We ascertained employment, health, and demographic information on 499 current wildland firefighters (WLFFs) via questionnaire.

RESULTS

Relative to those with less than 10 years of experience as a WLFF, those with 10-19 years of experience had significantly greater odds of having ever been diagnosed with hypertension, as did those with 20 or more years of experience. Significant associations were observed for report of physician-diagnosed heart arrhythmia and previous knee surgery.

CONCLUSIONS

We observed significant links between a greater number of years as a WLFF and self-report of two subclinical cardiovascular risk factors as well as markers of musculoskeletal health. Additional studies are needed to determine if findings can be generalized to all WLFFs.

Multiple Days of Heat Exposure on Firefighters' Work Performance and Physiology

This study assessed the accumulated effect of ambient heat on the performance of, and physiological and perceptual responses to, intermittent, simulated wildfire fighting tasks over three consecutive days. Firefighters (n = 36) were matched and allocated to either the CON (19°C) or HOT (33°C) condition. They performed three days of intermittent, self-paced simulated firefighting work, interspersed with physiological testing. Task repetitions were counted (and converted to distance or area) to determine work performance. Participants were asked to rate their perceived exertion and thermal sensation after each task. Heart rate, core temperature (Tc), and skin temperature (Tsk) were recorded continuously throughout the simulation. Fluids were consumed ad libitum. Urine volume was measured throughout, and urine specific gravity (USG) analysed, to estimate hydration. All food and fluid consumption was recorded. There was no difference in work output between experimental conditions. However, significant variation in performance responses between individuals was observed. All measures of thermal stress were elevated in the HOT, with core and skin temperature reaching, on average, 0.24 ± 0.08°C and 2.81 ± 0.20°C higher than the CON group. Participants' doubled their fluid intake in the HOT condition, and this was reflected in the USG scores, where the HOT participants reported significantly lower values. Heart rate was comparable between conditions at nearly all time points, however the peak heart rate reached each circuit was 7 ± 3% higher in the CON trial. Likewise, RPE was slightly elevated in the CON trial for the majority of tasks. Participants' work output was comparable between the CON and HOT conditions, however the performance change over time varied significantly between individuals. It is likely that the increased fluid replacement in the heat, in concert with frequent rest breaks and task rotation, assisted with the regulation of physiological responses (e.g., heart rate, core temperature).

Absolute vs. weight-related maximum oxygen uptake in firefighters: fitness evaluation with and without protective clothing and self-contained breathing apparatus among age group

During fire emergencies, firefighters wear personal protective devices (PC) and a self-contained breathing apparatus (S.C.B.A.) to be protected from injuries. The purpose of this study was to investigate the differences of aerobic level in 197 firefighters (age: 34±7 yr; BMI: 24.4±2.3 kg.m^-2), evaluated by a Queen’s College Step field Test (QCST), performed with and without fire protective garments, and to analyze the differences among age groups (<25 yr; 26-30 yr, 31-35 yr, 36-40 yr and >40 yr). Variance analysis was applied to assess differences (p < 0.05) between tests and age groups observed in absolute and weight-related values, while a correlation was examined between QCST with and without PC+S.C.B.A. The results have shown that a 13% of firefighters failed to complete the test with PC+S.C.B.A. and significant differences between QCST performed with and without PC+S.C.B.A. in absolute (F_(1,169) = 42.6, p < 0.0001) and weight-related (F_(1,169) = 339.9, p < 0.0001) terms. A better correlation has been found in L•min^-1 (r=0.67) than in ml•kg^-1•min^-1 (r=0.54). Moreover, we found significant differences among age groups both in absolute and weight-related values. The assessment of maximum oxygen uptake of firefighters in absolute term can be a useful tool to evaluate the firefighters' cardiovascular strain.

Fluid intake, hydration, work physiology of wildfire fighters working in the heat over consecutive days

PURPOSE

(i) To evaluate firefighters' pre- and post-shift hydration status across two shifts of wildfire suppression work in hot weather conditions. (ii) To document firefighters' fluid intake during and between two shifts of wildfire suppression work. (iii) To compare firefighters' heart rate, activity, rating of perceived exertion (RPE), and core temperature across the two consecutive shifts of wildfire suppression work.

METHOD

Across two consecutive days, 12 salaried firefighters' hydration status was measured immediately pre- and post-shift. Hydration status was also measured 2h post-shift. RPE was also measured immediately post-shift on each day. Work activity, heart rate, and core temperature were logged continuously during each shift. Ten firefighters also manually recorded their food and fluid intake before, during, and after both fireground shifts.

RESULTS

Firefighters were not euhydrated at all measurement points on Day one (292±1 mOsm l(-1)) and euhydrated across these same time points on Day two (289±0.5 mOsm l(-1)). Fluid consumption following firefighters' shift on Day one (1792±1134ml) trended (P = 0.08) higher than Day two (1108±1142ml). Daily total fluid intake was not different (P = 0.27), averaging 6443±1941ml across both days. Core temperature and the time spent ≥ 70%HRmax were both elevated on Day one (when firefighters were not euhydrated). Firefighters' work activity profile was not different between both days of work.

CONCLUSION

There was no difference in firefighters' pre- to post-shift hydration within each shift, suggesting ad libitum drinking was at least sufficient to maintain pre-shift hydration status, even in hot conditions. Firefighters' relative hypohydration on Day one (despite a slightly lower ambient temperature) may have been associated with elevations in core temperature, more time in the higher heart rate zones, and 'post-shift' RPE.

Working in hot conditions--a study of electrical utility workers in the northern territory of Australia

Environmental conditions of Australia's Northern Territory are seasonally conducive to excessive body heat storage by outdoor workers. For electrical utility workers who periodically work at height, in confined space, and in proximity to live power sources, the impact of the climate may be considered a hazardous condition. Therefore, this study examined the physiological and fluid balance responses of 20 power network workers (31.5 years; 86.0 kg; 1.71 m; BMI 29.5) throughout work shifts in the Northern and Southern regions of the Northern Territory, Australia. Twenty male heat-acclimatized power network workers provided written informed consent to be monitored during maintenance of electrical infrastructure that included replacing power pole components and transformer and substation repairs in the Northern (n = 13) and Southern regions (n = 7) of the Northern Territory (mean wet-bulb globe temperatures of 32.0°C and 28.7°C, respectively). An ingestible telemetry pill provided measurement of gastrointestinal temperature (Tgi), that when combined with heart rate values, provided physiological strain index (PSI). Urine specific gravity, sweat rate, and level of dehydration were also determined. The Tgi values of this study were within the ISO9886 limit for monitored, heat-acclimatized workers, with a peak of 38.4°C. Mean PSI was 2.6, which represents overall low strain, with periods of moderate strain. Urinary analysis indicated that workers were dehydrated prior to and following the work shift, however the mean sweat rate of 0.44 L.h(-1) was matched by fluid consumption of 0.42 L.h(-1) to limit body mass loss to 0.1% during the shift. This study demonstrates that heat acclimatized electrical utility workers adhere to ISO9886 requirements when undertaking self-paced activity in hot conditions.

The effect of pre-warming on performance during simulated firefighting exercise

This study examined the effect of active pre-warming on speed and quality of performance during simulated firefighting exercise. Twelve male firefighters performed two trials in counterbalanced order. They were either pre-warmed by 20-min cycling at 1.5 Watt kg(-)(1) body mass (WARM) or remained thermoneutral (CON) prior to a simulated firefighting activity. After the pre-warming, gastrointestinal temperature (P < 0.001), skin temperature (P = 0.002), and heart rate (P < 0.001) were higher in WARM than in CON. During the firefighting activity, rating of perceived exertion, thermal sensation and discomfort were higher for WARM than for CON. Finish time of the firefighting activity was similar, but the last task of the activity was completed slower in WARM than in CON (P = 0.04). In WARM, self-reported performance quality was lower than in CON (P = 0.04). It is concluded that pre-warming reduces the speed during the last part of simulated firefighting activity and reduces self-reported quality of performance.

The effects of ice slurry ingestion before exertion in Wildland firefighting gear

PURPOSE

To investigate the effect of ice slurry ingestion precooling on body core temperature (Tc) during exertion in wildland firefighting garments in uncompensable heat stress.

METHODS

On two separate trials, 10 males ingested 7.5 g·kg(-1) of either an ice slurry (0.1°C) or control beverage (20°C) during seated rest for 30 minutes prior to simulating the U.S. Forest Service Pack Test on a treadmill in wildland firefighting garments in a hot environment (38.8 ± 1.2°C, 17.5 ± 1.4% relative humidity). Deep gastric temperature, mean skin temperature (Tsk), and heart rate (HR) were recorded. Ratings of perceived exertion, thermal sensation, comfort, and sweating were assessed.

RESULTS

Compared with ingestion of a temperate beverage, precooling with ice slurry before exertion in a hot environment reduced Tc during the first 30 minutes of the exercise bout. Exercise time and distance completed were not different between treatments. Skin temperature, heart rate, and perceptual responses rose in both conditions during exercise but did not differ by condition.

CONCLUSION

Pretreatment with ice slurry prior to exertion in wildland firefighting garments results in a modest reduction in Tc during the first 30 minutes of exercise when compared to pretreatment with control beverage but the ice slurry precooling advantage did not persist throughout the 45-minute exercise protocol.

A review of heat transfer phenomena and the impact of moisture on firefighters' clothing and protection

Protective clothing with high insulation properties helps to keep the wearer safe from flames and other types of hazards. Such protection presents some drawbacks since it hinders movement and decreases comfort, in particular due to heat stress. In fact, sweating causes the accumulation of moisture which directly influences firefighters' performance, decreasing protection due to the increase in radiant heat flux. Vaporisation and condensation of hot moisture also induces skin burn. To evaluate the heat protection of protective clothing, Henrique's equation is used to predict the time leading to second-degree burn. The influence of moisture on protection is complex, i.e., at low radiant heat flux, an increase in moisture content increases protection, and also changes thermal properties. Better understanding of heat and mass transfer in protective clothing is required to develop enhanced protection and to prevent burn injuries.

PRACTITIONER SUMMARY

This paper aims to contribute to a better understanding of heat and mass transfer inside firefighters' protective clothing to enhance safety. The focus is on the influence of moisture content and the prevention of steam burn.

Trunk postures and upper-body muscle activations during physically demanding wildfire suppression tasks

This study examined the trunk postures and upper-body muscle activations during four physically demanding wildfire suppression tasks. Bilateral, wireless surface electromyography was recorded from the trapezius and erector spinae muscles of nine experienced, wildfire fighters. Synchronised video captured two retroreflective markers to allow for quantification of two-dimensional sagittal trunk flexion. In all tasks, significantly longer time was spent in the mild and severe trunk flexion (p ≤ 0.002) compared to the time spent in a neutral posture. Mean and peak muscle activation in all tasks exceeded previously established safe limits. These activation levels also significantly increased through the performance of each task (p < 0.001). The results suggest that the wildfire suppression tasks analysed impose significant musculoskeletal demand on firefighters. Fire agencies should consider developing interventions to reduce the exposure of their personnel to these potentially injurious musculoskeletal demands.