Core temperature and heart rate response to repeated bouts of firefighting activities

During live-fire firefighting operations and training evolutions, firefighters often consume multiple cylinders of air and continue to wear their personal protective equipment even after fire suppression activities have ceased. However, most studies have only reported core temperature changes during short-term firefighting activities and have shown a very modest increase in core temperature. Therefore, the purpose of this study is to evaluate core temperature and heart rate (HR) during repeated bouts of firefighting activity over ～3 h. The results of this study show that core temperatures increase by an average of 1.9°C – to a larger magnitude than previously reported – and continue to increase during subsequent work cycles (38.4 vs. 38.7) even after long breaks of more than 30 min. The rate of core temperature increase during work continues to increase later in the training exercise (from 0.036 to 0.048°C/min), increasing the risk for exertional heat stress particularly if long-duration firefighting activity is required at these later times.

Practitioner Summary: To date, core temperature and HR changes during firefighting have been reported for short-term studies, which may significantly underestimate the physiological burden of typical firefighting activities. Firefighter core temperatures are shown to increase to a larger magnitude than previously observed and the rate of rise in core temperature increases during subsequent firefighting activities.     

Physiological response to firefighting activities of various work cycles using extended duration and prototype SCBA

Firefighters’ self-contained breathing apparatus (SCBA) protects the respiratory system during firefighting but increases the physiological burden. Extended duration SCBA (>30 min) have increased air supply, potentially increasing the duration of firefighting work cycles. To examine the effects of SCBA configuration and work cycle (length and rest), 30 firefighters completed seven trials using different SCBA and one or two bouts of simulated firefighting following work cycles common in the United States. Heart rate, core temperature, oxygen consumption, work output and self-reported perceptions were recorded during all activities. Varying SCBA resulted in few differences in these parameters. However, during a second bout, work output significantly declined while heart rates and core temperatures were elevated relative to a single bout. Thirty seven per cent of the subjects were unable to complete the second bout in at least one of the two-bout conditions. These firefighters had lower fitness and higher body mass than those who completed all assigned tasks.

Practitioner Summary: The effects of extended duration SCBA and work/rest cycles on physiological parameters and work output have not been examined. Cylinder size had minimal effects, but extended work cycles with no rest resulted in increased physiological strain and decreased work output. This effect was more pronounced in firefighters with lower fitness.     

Firefighter exercise protocols conducted in an environmental chamber: developing a laboratory-based simulated firefighting protocol

Abstract

A standard exercise protocol that allows comparisons across various ergonomic studies would be of great value for researchers investigating the physical and physiological strains of firefighting and possible interventions for reducing the demands. We compared the pattern of cardiorespiratory changes from 21 firefighters during simulated firefighting activities using a newly developed firefighting activity station (FAS) and treadmill walking both performed within an identical laboratory setting. Data on cardiorespiratory parameters and core temperature were collected continuously using a portable metabolic unit and a wireless ingestible temperature probe. Repeated measures ANOVA indicated distinct patterns of change in cardiorespiratory parameters and heart rate between conditions. The pattern consisted of alternating periods of peaks and nadirs in the FAS that were qualitatively and quantitatively similar to live fire activities, whereas the same parameters increased logarithmically in the treadmill condition. Core temperature increased in a similarly for both conditions, although more rapidly in the FAS.

Practitioner Summary: The firefighting activity station (FAS) yields a pattern of cardiorespiratory responses qualitatively and quantitatively similar to live fire activities, significantly different than treadmill walking. The FAS can be performed in a laboratory/clinic, providing a potentially standardised protocol for testing interventions to improve health and safety and conducting return to duty decisions.     

Selected physiological and psychobiological responses to physical activity in different configurations of firefighting gear

The aim was to examine selected physiological and psychobiological responses to different configurations of protective firefighting gear. Career firefighters (n = 10) walked on a treadmill (3·5?km · h^?1, 10% grade) for 15?min in three different clothing configurations. On separate days subjects wore: (a) ‘station blues’, (b) a hip boot configuration of firefighting gear, and (c) the current ‘NFPA 1500 standard’ gear. Physiological, psychophysical, and psychological measurements were recorded pre-exercise (5?min), during exercise (15?min), and during post-exercise recovery (10min). Repeated measures ANOVA revealed significant main effects for condition, time, and interaction (p < 0·001) for heart rate (HR), rectal temperature, mean skin temperature, oxygen consumption, breathing distress, thermal sensations, and affect. Furthermore, post hoc analyses revealed that all variables were significantly higher in the NFPA 1500 standard versus the hip boot or the station blues clothing configurations. These data suggest that the current NFPA 1500 standard configuration results in greater physiological and psychobiological stress at a given workload.     

Selected physiological and psychological responses to live-fire drills in different configurations of firefighting gear

The purpose of this study was to examine selected physiological and psychological responses to strenuous live-fire drills in different configurations of protective firefighting gear. Career firefighters (n = 10) performed three sets of firefighting drills in a training structure that contained live fires in two different configurations of firefighting gear. On separate days subjects wore: (a) the NFPA 1500 (1987) standard configuration, and (b) a hip-boot configuration of the firefighting gear. Physiological and psychological measurements were recorded pre-activity and at the end of each trial. Repeated measures ANOVA revealed a strong trend for performance time to be greater in the 1500 gear than in the hipboot gear. There was a significant Time × Gear interaction for tympanic membrane temperature, with temperature being greater in the 1500 gear. Perceptions of effort and thermal sensations were also greater in the 1500 gear than in the hip-boot configuration of the gear. There was little difference in mean performance on cognitive function measures between the two gear configurations, but there was greater variability in performance in the 1500 gear. These data suggest that performing strenuous firefighting drills in the current NFPA 1500 standard configuration results in longer performance time, greater thermal strain, and greater perception of effort and thermal sensation.     

Physiological strain of next generation combat uniforms with chemical and biological protection: importance of clothing vents

This study examined whether vents in the arms, legs and chest of new protective assault uniforms (PTAU) reduced heat strain at 35°C during a low dressed state (DS_low), and subsequently improved tolerance time (TT) after transitioning to DS_high compared with the battle dress uniform and overgarment (BDU+O). Small but significant reductions in rectal temperature (T _re), heart rate and vapour pressures over the thigh and shin were observed during DS_low with vents open (37.9 ± 0.2°C, 120 ± 10 b/min, 3.7 ± 0.4 and 3.5 ± 1.0 kPa) versus closed (38.0 ± 0.1°C, 127 ± 5 b/min, 4.3 ± 0.3 and 4.6 ± 0.5 kPa). During DS_high T _re was reduced and TT increased significantly with the PTAUs (1.1 ± 0.2°C/h and 46 ± 24 min) versus BDU+O (1.6 ± 0.2°C/h and 33 ± 16 min). The vents marginally reduced heat strain during DS_low and extended TT during DS_high compared with BDU+O.

Practitioner Summary: Clothing vents in chemical and biological protective uniforms can assist with heat transfer in situations where the uniforms must be worn for extended periods prior to exposure to a hazardous condition. Once the vents are closed, exposure time is increased and the increase in body temperature reduced.     

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

The aim of this study was to analyse the physiological strain of firefighters, using heart rate (HR) and core temperature, during real wildfire suppression according to the type of attack performed (direct, indirect or mixed). Threeintensity zones were established according to the HR corresponding to the ventilatory threshold (VT) and respiratory compensation threshold (RCT): zone 1, <VT; zone 2 (Z2), between VT and RCT; zone 3 (Z3), >RCT. The exercise workload (training impulse (TRIMP)), the physiological strain index (PSI) and the cumulative heat strain index(CHSI) were calculated using the time spent in each zone, and the HR and core temperature, respectively. Significantly higher mean HR, time spent in Z2 and Z3 and TRIMP h^?1 were found in direct and mixed versus indirect attacks. The highest PSI and CHSI were observed in the direct attack. In conclusion, exercise strain and combined thermal strain, but not core temperature during wildfire suppression, are related to the type of attack performed.

Statement of relevance: Our findings demonstrated that wildfire firefighting is associated with high physiological demands, which vary significantly depending on the tactics chosen for performing the task. These results should be kept in mind when planning programmes to improve wildland firefighters' physical fitness, which will allow improvement in their performance.     

Effect of base layer materials on physiological and perceptual responses to exercise in personal protective equipment

Ten men (non-firefighters) completed a 110 min walking/recovery protocol (three 20-min exercise bouts, with recovery periods of 10, 20, and 20 min following successive bouts) in a thermoneutral laboratory while wearing firefighting personal protective equipment over one of four base layers: cotton, modacrylic, wool, and phase change material. There were no significant differences in changes in heart rate, core temperature, rating of perceived exertion, thermal discomfort, and thermal strain among base layers. Sticking to skin, coolness/hotness, and clothing humidity sensation were more favorable (p < 0.05) for wool compared with cotton; no significant differences were identified for the other 7 clothing sensations assessed. Separate materials performance testing of the individual base layers and firefighting ensembles (base layer + turnout gear) indicated differences in thermal protective performance and total heat loss among the base layers and among ensembles; however, differences in heat dissipation did not correspond with physiological responses during exercise or recovery.     

Physiological responses to simulated firefighter exercise protocols in varying environments

For decades, research to quantify the effects of firefighting activities and personal protective equipment on physiology and biomechanics has been conducted in a variety of testing environments. It is unknown if these different environments provide similar information and comparable responses. A novel Firefighting Activities Station, which simulates four common fireground tasks, is presented for use with an environmental chamber in a controlled laboratory setting. Nineteen firefighters completed three different exercise protocols following common research practices. Simulated firefighting activities conducted in an environmental chamber or live-fire structures elicited similar physiological responses (max heart rate: 190.1 vs 188.0 bpm, core temperature response: 0.047°C/min vs 0.043°C/min) and accelerometry counts. However, the response to a treadmill protocol commonly used in laboratory settings resulted in significantly lower heart rate (178.4 vs 188.0 bpm), core temperature response (0.037°C/min vs 0.043°C/min) and physical activity counts compared with firefighting activities in the burn building.

Practitioner Summary: We introduce a new approach for simulating realistic firefighting activities in a controlled laboratory environment for ergonomics assessment of fire service equipment and personnel. Physiological responses to this proposed protocol more closely replicate those from live-fire activities than a traditional treadmill protocol and are simple to replicate and standardise.     

Thermal sensation of the body as influenced by the thermal microclimate in a face mask

Subjective and physiological responses were obtained from six subjects wearing a face mask while exercising (220 W m ^?2) for 15 min on a bicycle ergometer. Different combinations of ambient air temperatures (7, 16 and 25°C) and mask air temperatures (22,27 and 33°C) were studied with two different air humidities inside the mask (61 and 86% relative humidity (RH)). Control experiments were performed without the mask at the same ambient temperatures. Skin temperatures, heart rates and skin wettedness were monitored during exercise. The subjects’ thermal sensations, sensations of sweating and skin wettedness and their thermal preferences were assessed at the end of the exercise period. Whole body thermal sensation was primarily determined by the ambient air temperature, but was also significantly influenced by the mask air temperature. This could only partly be explained by the change in respiratory heat loss. Other possible avenues of influence are discussed.     

Gender-related difference in sweat loss and its impact on exposure limits to heat stress

The aim of this study was to evaluate the validity of the recently proposed predicted heat strain (PHS) model with respect to gender, particularly in relation to the estimation of admissible exposure durations for work in hot environments. Two experiments addressing the effects of the climatic conditions inside vehicles during summer with altogether 96 females and 114 males were analysed. Each subject was exposed for 2 h to a typical summer climate. Highly significant gender-related differences were found for the observed sweat rates. When adjusting the sweat rate to anthropometric measures the differences remained statistically significant, even if females and males were matched for body surface area or surface-to-mass ratio. There is much evidence in the literature that gender-related differences in sweat loss diminish once they are adjusted to anthropometric variables or to physical fitness. However, thermal indices like the PHS model rely on absolute values of the physiological response to heat stress. Therefore, a systematic overestimation of the sweat loss for women could imply an underestimation of body heat storage and core temperature accordingly. A possible approach to revised limit values in the PHS model could be to reduce the values of the maximum sweat rate for women.

Relevance to industry

Work in hot environments is still present at many industrial workplaces, particulary in underdeveloped countries. International standards provide exposure limits for the prevention of heat disorders. The results of this study indicate that these limits should be revised with respect to gender-related differences in sweat loss.     

The impact of various rehydration volumes for firefighters wearing protective clothing in warm environments

This study examined different fluid replacement quantities during intermittent work while wearing firefighting protective clothing and self-contained breathing apparatus in the heat (35°C, 50% relative humidity). Twelve firefighters walked at 4.5 km per h with 0% elevation on an intermittent work (50 min) and rest (30 min) schedule until they reached a rectal temperature of 39.5°C during work periods and 40.0°C during rest, heart rates of 95% of maximum and/or exhaustion. During the heat-stress trials subjects received one of four fluid replacement quantities, high (H), moderate (M), low (L), and no hydration (NH), where H, M and L represented 78%, 63% and 37% of fluid loss, respectively. The total tolerance time (work + rest) was significantly greater during H (111.8 ± 3.5), M (112.9 ± 5.2) and L (104.2 ± 5.8) compared to NH (95.3 ± 3.8). In addition, work time (min), which excluded rest periods, was significantly greater in H (82.6 ± 3.5), and M (82.9 ± 5.2) compared to NH (65.3 ± 3.8). It is concluded that incorporating even partial fluid replacement strategies while wearing firefighting protective clothing and self-contained breathing apparatus in the heat improves tolerance time.     

基于监测的空间网格结构应力应变分析

为保障大跨度空间结构的安全运营,以厦门高铁站房钢屋盖为研究对象,分析其应力、应变监测数据受温度载荷影响的特性,拟合结构应力和温度的线性变化关系。基于拟合线性关系,依据结构特点,提出测点数据基于温度相关性和测点相关性的数据缺失插补方法。通过对应力、应变监测数据的分析处理,更加直接全面了解大跨空间结构的受力情况,为其正常运营提供有力依据。     

受火钢拱结构的冲击响应与弯扭屈曲

为研究火灾中受质量块撞击两端固支钢拱结构的动力响应和弯扭屈曲行为,利用有限元软件Abaqus对其进行数值仿真,考虑钢材力学性能的升温退化和应变率强化效应,得到临界温度范围内钢拱发生弯扭屈曲时质量块的临界速度,以及撞击荷载作用下钢拱结构的竖向挠度、撞击力变化曲线和响应过程,并对质量块的质量 速度关系和拱脚处约束条件进行参数分析。研究结果表明,在不同温度范围内,使钢拱发生弯扭屈曲的质量块临界速度的影响因素不同：20 ℃≤T≤100 ℃时,静载荷比η起主要作用;100 ℃相似文献   

Comparison of two different cooling systems in alleviating thermal and physiological strain during prolonged exercise in the heat

Abstract

This study compared the efficacy of an ice vest comprising of water (WATER) or a water-carbon (CARBON) emulsion on thermophysiological responses to strenuous exercise in the heat. Twelve male cyclists completed three 50-minute constant workload trials (55% of peak power output, ambient temperature 30.4?±?0.6°C) with WATER, CARBON, and without ice vest (CONTROL), respectively. The increase in core body temperature (Tcore) was lower in WATER at 40 (?0.49?±?0.34 °C) and 50?minutes (?0.48?±?0.48 °C) and in CARBON at 30 (?0.41?±?0.48 °C), 40 (?0.54?±?0.51 °C), and 50?minutes (?0.67?±?0.62 °C) as compared to CONTROL (p?<?0.05, ES > 0.8). While heart rate and blood lactate kinetics did not differ between the conditions, statistical main effects in favour of both WATER and CARBON were found for thermal sensation (condition p?<?0.001 and interaction p?<?0.01) and rating of perceived exertion (condition p?<?0.05). Per-cooling with CARBON and WATER similarly reduced Tcore but not physiological strain during prolonged exercise in the heat.

Practitioner Summary: Exercise in the heat is characterised by increases in thermophysiological strain. Both per-cooling with a novel carbon-based and a conventional water-based ice vest were shown to reduce core temperature significantly. However, due to its lower mass, the carbon-based system may be recommended especially for weight-bearing sports.     

The effects of multiple firefighting activities on information processing and work performance in a smoke‐diving room: An intervention study

Firefighters perform various tasks during firefighting operations under unknown and unpredictable conditions. The present study investigated the impact of firefighting activities and cooling tactics on information processing and work performance. Firefighters performed typical firefighting tasks in the four experimental conditions, namely i) no cooling device (NC), ii) cooling gel (CG), iii) cool vest (CV), and iv) cooling gel and cool vest (CG + CV). The measurement of information processing, Paced Auditory Serial Addition Test (PASAT) scores decreased significantly after the firefighting activities in the four conditions, relative to baseline. The results revealed no significant difference in PASAT scores among the four conditions. However, the performance time (PT) was significantly shorter for the CV and CG + CV compared to the NC and CG conditions. The findings confirmed that the firefighting activities have a detrimental effect on information processing. The CG + CV and CV were more effective than CG and NC in improving PT during firefighting. However, the cooling strategies have a negligible effect on improving information processing performance.     

Component contribution of personal protective equipment to the alleviation of physiological strain in firefighters during work and recovery

The purpose of this study was to investigate the components contributions of personal protective equipment on physiological strain in firefighters during exercise and recovery. Eight firefighters participated in trials in which various combinations of personal protective equipment components weighing from 1.3 to 15.1 kg were worn. The results showed that rectal temperature, changes in rectal temperature, mean skin temperature, heart rate, oxygen consumption and blood lactate concentration were smaller in conditions without boots (no-boots) than in other conditions with no helmet, gloves or self-contained breathing apparatus (P < 0.05). Increases in rectal temperature per unit mass of personal protective equipment were approximately twice as small in no-boots condition as the other conditions. These results suggest that the reduction of the boots' mass might be more efficient to alleviate heat strain of firefighters wearing personal protective equipment, rather than the reduction of the mass of self-contained breathing apparatus, helmet or gloves.     

Occupational stress in submariners: The impact of isolated and confined work on psychological well-being

This study aimed to identify work-related and personal factors associated with occupational stress in submariners. Work and well-being questionnaires were distributed to 219 male submariners (mean age 34 years), as part of a larger cohort study involving a stratified sample of 4951 Royal Navy (RN) personnel. The stress rate in submariners was 40%; significantly higher than the stress rate in the general RN, although once demographic factors were controlled for in a matched control sample, this difference was no longer significant. A summary model accounted for 49% of the variance in submariner stress, with key differences emerging between the occupational factors associated with stress in submariners and in the general RN. The longitudinal nature of this study permits stress in submariners to be monitored over 5 years, which will provide valuable insights into the chronicity of stress in this specialised occupational group.

Statement of Relevance: This paper contributes to the current literature on the negative impact of working in isolated conditions. It is demonstrated that occupational stress in submarines can be partially explained using current theories of stress in the workplace. However, the constraints of a restricted environment introduce additional factors which can also be associated with occupational stress.     

Innovation in IT firms: An investigation of intramural and extramural R&D activities and their impact

This research examines how intramural activities that are developed internally within the firm and extramural activities that are undertaken in collaboration with an external partner lead to product and process innovation. We use hierarchical regression analysis on data collected for European and Chinese firms and determine that intramural activities have a profound positive impact on process innovation, whereas their impact on product innovation is positive only for large firms. We discover that process innovation positively impacts product innovation but not vice versa. The results are important for managers who guide the R&D activities of a firm to product and process innovation.