Response to thermal and physical strain during flashover training in Croatian firefighters

Flashover training (FOT) for firefighters is a simulation of the flashover phenomenon under controlled conditions. This study assessed arterial blood pressure (BP) and its response to thermal and physical strain during FOT in 48 professional and 18 volunteer firefighters.     

Immune and inflammatory responses of Australian firefighters after repeated exposures to the heat

When firefighters work in hot conditions, altered immune and inflammatory responses may increase the risk of a cardiac event. The present study aimed to establish the time course of such responses. Forty-two urban firefighters completed a repeat work protocol in a heat chamber (100 ± 5°C). Changes to leukocytes, platelets, TNFα, IL-6, IL-10, LPS and CRP were evaluated immediately post-work and also after 1 and 24 h of rest. Increases in core temperatures were associated with significant increases in leukocytes, platelets and TNFα directly following work. Further, platelets continued to increase at 1 h (+31.2 ± 31.3 × 10⁹ l, p < 0.01) and remained elevated at 24 h (+15.9 ± 19.6 × 10⁹ l, p < 0.01). Sustained increases in leukocytes and platelets may increase the risk of cardiac events in firefighters when performing repeat work tasks in the heat. This is particularly relevant during multi-day deployments following natural disasters.

Practitioner Summary: Firefighters regularly re-enter fire affected buildings or are redeployed to further operational tasks. Should work in the heat lead to sustained immune and inflammatory changes following extended rest periods, incident controllers should plan appropriate work/rest cycles to minimise these changes and any subsequent risks of cardiac events.     

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.     

Physiological responses of firefighters and performance predictors during a simulated rescue of hospital patients

There is incomplete information about how physically demanding rescue work may be. The aim therefore of this paper was to examine the physiological responses of firefighters during a simulated rescue of hospital patients and to relate the firefighters' performance to their endurance, strength and working technique. Fourteen part-time male firefighters with a maximal oxygen uptake (VO_2max) of 4.4 ± 0.3 l/min (mean ± SD) served as subjects in this study. First, each firefighter ascended six floors (a 20.5 m vertical ascent) carrying tools, wearing protective clothing and a breathing apparatus, an extra mass of 37 kg. He thereafter ‘rescued’ six persons by dragging each person on a fire-sheet on a flat floor. The technique used was recorded and the O₂ uptake and the heart rate were measured continuously during the whole operation. The blood lactate concentration and the subjective rating of perceived exertion were measured during and just after the rescue. The VO_2max and the muscle strength were measured in the laboratory. The whole operation was carried out in the course of 5–9 min. The operation was a virtual all-out effort and the peak blood lactate concentration was 13 ± 3 mmol/l. The peak oxygen uptake was 3.7 ± 0.5 l/min (84% of the VO_2max) during the operation. Large and heavy firefighters carried out the task faster than smaller ones. The VO_2max in absolute terms and the dragging technique used were both related to the rescue performance. Rescuing patients at a hospital was physically very demanding and the time needed to complete the task depended on the VO_2max in absolute values and the working technique used. A minimum VO_2max of 4 l/min for firefighters was recommended.     

Physiological responses of firefighters and performance predictors during a simulated rescue of hospital patients

There is incomplete information about how physically demanding rescue work may be. The aim therefore of this paper was to examine the physiological responses of firefighters during a simulated rescue of hospital patients and to relate the firefighters' performance to their endurance, strength and working technique. Fourteen part-time male firefighters with a maximal oxygen uptake (VO(2max)) of 4.4 +/- 0.3 l/min (mean +/- SD) served as subjects in this study. First, each firefighter ascended six floors (a 20.5 m vertical ascent) carrying tools, wearing protective clothing and a breathing apparatus, an extra mass of 37 kg. He thereafter 'rescued' six persons by dragging each person on a fire-sheet on a flat floor. The technique used was recorded and the O(2) uptake and the heart rate were measured continuously during the whole operation. The blood lactate concentration and the subjective rating of perceived exertion were measured during and just after the rescue. The VO(2max) and the muscle strength were measured in the laboratory. The whole operation was carried out in the course of 5-9 min. The operation was a virtual all-out effort and the peak blood lactate concentration was 13 +/- 3 mmol/l. The peak oxygen uptake was 3.7 +/- 0.5 l/min (84% of the VO(2max)) during the operation. Large and heavy firefighters carried out the task faster than smaller ones. The VO(2max) in absolute terms and the dragging technique used were both related to the rescue performance. Rescuing patients at a hospital was physically very demanding and the time needed to complete the task depended on the VO(2max) in absolute values and the working technique used. A minimum VO(2max) of 4 l/min for firefighters was recommended.     

Comparing speakers versus headphones in listening to news from a computer – individual differences and psychophysiological responses

When audio is listened with speakers, the sound comes from a distance. With headphones, the surrounds are more isolated and the sound comes closer to the listener, and may thus create a more intimate and immersive listening experience. We examined the emotion-related subjective and psychophysiological responses elicited when listening news from a computer with speakers versus headphones, and the individual differences in these responses. Self-reported preference, valence, arousal, and understandability of the news, as well as electrodermal activity (EDA), pulse transit time (PTT), respiratory sinus arrhythmia (RSA), and facial electromyography (EMG), were measured.     

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.     

Reliability of physiological and subjective responses to physical and psychosocial exposures during a simulated manufacturing task

Responses to physical and psychosocial exposures can be measured using diverse methods, but their reliability, particularly under multiple exposures, is largely unknown. Five classes of methods were used to assess physiological and subjective responses among 24 participants to four combinations of physical and psychosocial exposures while performing two identical sessions of a simulated overhead manufacturing task. As an exploratory analysis, test–retest reliability was quantified using intraclass correlation coefficients (ICC) and coefficients of variation (CV). Discomfort ratings were reliable under less favorable exposures, and ratings of the psychosocial environment were most reliable under favorable social support. Workload ratings were most reliable with high physical exposure and favorable social support, and task performance was reliable overall. EMG and heart rate had relatively low reliability. Slightly less than half of the variables were considered reliable, but reliability depended on exposure conditions.Relevance to industry: The study provides information on the reliability of commonly used exposure measurement methods. The results can guide the selection of physiological and psychological work outcome measurements in future studies and work evaluations.     

Work tolerance and subjective responses to wearing protective clothing and respirators during physical work

This study examined work tolerance and subjective responses while performing two levels of work and wearing four types of protective ensembles. Nine males (mean age = 24·8 years, weight = 75·3 kg, [Vdot]O₂ max = 44·6 ml/kg min) each performed a series of eight experimental tests in random order, each lasting up to 180 min in duration. Work was performed on a motor-driven treadmill at a set walking speed and elevation which produced work intensities of either 30% or 60% of each subject's maximum aerobic capacity. Work/rest intervals were established based on anticipated SCBA refill requirements. Environmental temperature averaged 22·6°C and average relative humidity was 55%. The four protective ensembles were: a control ensemble consisting of light work clothing (CONTROL); light work clothing with an open circuit self-contained breathing apparatus (SCBA); firefighter's turnout gear with SCBA (FF); and chemical protective clothing with SCBA (CHEM). Test duration (tolerance time) was determined by physiological responses reaching a predetermined indicator of high stress or by a 180-min limit. Physiological and subjective measurements obtained every 2·5 min included: heart rate, skin temperature, rectal temperature, and subjective ratings of perceived exertion, thermal sensation, and perspiration.

The mean tolerance times were 155, 130, 26, and 73 min, respectively, for the CONTROL, SCBA, FF, and CHEM conditions during low intensity work; and 91, 23, 4, and 13 min, respectively, during high intensity work. Differences between ensemble and work intensity were significant FF and CHEM heart rate responses did not reach a steady state, and rose rapidly compared to CONTROL and SCBA values. SCBA heart rates remained approximately 15 beats higher than the CONTROL ensemble during the tests. At the low work intensity, mean skin.     

Muscle- and task-dependent responses to concurrent physical and mental workload during intermittent static work

Many workers experience combined physical and mental demands in their jobs, yet the contribution of these demands to the development of musculoskeletal disorders is unclear. The purpose of this study was to investigate muscle- and task-dependent responses to concurrent demands during intermittent static work. Twenty-four participants performed shoulder, wrist, and torso exertions at three levels of physical workload (PWL) in the absence (control) and presence (concurrent) of a mental arithmetic task. Compared to the control, concurrent demand conditions resulted in decreased muscle activity (4–9% decrease), increased cardiovascular load (2–4% increase), and impaired motor co-ordination (9–24% increase in force fluctuation). Furthermore, these outcomes were more prominent at higher PWL levels and within postural (shoulder and torso) muscles. Mental task performance exhibited greater interference with the physical task at low and high PWL levels. Thus, it may be important to consider these muscle- and task-specific interactions of concurrent demands during job design to address worker health and performance issues.

Practitioner Summary: Occupational tasks place both physical and mental demands on workers. These demands can adversely affect physiological responses and performance, and are muscle- and task-dependent. Findings from this research may facilitate the development of ergonomics interventions, such as task redesign and tool/workstation design, that may help reduce risk of workplace injuries.     

Stress management in the workplace: A comparison of a computer-based and an in-person stress-management intervention

Work stress contributes significantly to corporate health costs. Numerous corporations have implemented worksite stress-management interventions to mitigate the financial and personal impact of stress on their employees. Cognitive-behavioral stress-management interventions can reduce both perceived and physiologically measured stress. Traditionally, these interventions have been delivered in small, instructor-led groups. Outcomes from a stress-management intervention provided via an instructor led versus a computer-presented format were compared through a randomized, controlled design. Brief relaxation procedures presented in both formats led to highly significant reductions in immediately-reported stress. Stress reduction, however, was not associated with improvement in longer-term indices of workplace stress following completion of the intervention and at a one-month follow-up. Attrition was significantly higher in the computer-presentation format. Across both presentation formats, however, more frequent use of stress-reduction techniques was correlated significantly with greater reductions in stress indices (e.g., nervousness, social isolation, overall work stress) at follow-up.     

Physiological and biomechanical responses to a prolonged repetitive asymmetric lifting activity

This study investigated the effects of a prolonged repetitive asymmetric lifting task on behavioural adaptations during repetitive lifting activity, measures of tissue oxygenation and spine kinematics. Seventeen volunteers repeatedly lifted a box, normalised to 15% of the participant's maximum lifting strength, at the rate of 10 lifts/min for a period of 60 min. The lifts originated in front of the participants at ankle level and terminated on their left side at waist level. Overall, perceived workload increased during the repetitive lifting task. Erector spinae oxygenation levels, assessed using near-infrared spectroscopy, decreased significantly over time. Behavioural changes observed during the repetitive lifting task included increases in the amount of forward bending, the extension velocity and the lateral bending velocity, and a reduced lateral bending moment on the spine. These changes, with the exception of the reduced lateral bending moment, are associated with increased risk of low back disorder.     

Examining the relationship between job design and worker strain over time in a sample of office workers

This study examines relationships between job design variables and worker strain. Office workers from a public service organization participated in a three-year study. Once during each of the three years, the same questionnaire was handed out to the subjects to examine job design and worker strain. The results indicate that the bivariate relationships between job design and worker strain change over time. At round 1, quantitative workload, work pressure and supervisor social support were the most important predictors of the worker strain variables. At round 2, task clarity, supervisor social support, and job future ambiguity were the most important predictors of worker strain. At round 3, task clarity, attention, and job future ambiguity were the most consistent predictors of worker strain. The results of the canonical correlation analysis were relatively similar for rounds 1 and 3, but not for round 2. There appears to be some consistency in the overall underlying structure of the relationships between job design and worker strain, but there is also some inconsistency in terms of which specific job design factors are related to specific measures of worker strain.     

The effect of two kinds of T-shirts on physiological and psychological thermal responses during exercise and recovery

The aim of this study was to investigate the physiological and psychological responses during and after high-intensity exercise in a warm and humid environment in subjects wearing shirts of different fabrics. Eight healthy men exercised on two separate occasions, in random order, wearing two types of long-sleeve T-shirt: one made of polyester (PES) and the other of cotton fabric (CT). They performed three 20 min exercise bouts, with 5 min rest between each, and then rested in a chair for 60 min to recover. The ambient temperature was 25 °C and relative humidity was 60%. The exercise comprised of treadmill running at 8 km/h at 1° grade. Rectal temperature, skin temperatures at eight sites, heart rate, T-shirt mass and ratings of thermal, clothing wettedness, and shivering/sweating sensation were measured before the experiment, during the 5 min rest period after each exercise bout, and during recovery. Nude body mass was measured before the experiment and during recovery. The physiological stress index showed that the exercise produced a state of very high heat stress. Compared with exercise wearing the CT shirt, exercise wearing the PES fabric produced a greater sweating efficiency and less clothing regain (i.e., less sweat retention), but thermophysiological and subjective sensations during the intermittent high-intensity exercise were similar for both fabrics. However, skin temperature returned to the pre-exercise level faster, and the thermal and rating of shivering/sweating sensation were lower after exercise in the warm and humid environment in subjects wearing PES than when wearing the more traditional CT fabric.     

The contribution of email volume,email management strategies and propensity to worry in predicting email stress among academics

The present study explored the contribution of email volume, email management and worry in predicting email stress among a sample of Australian academics. The sample comprised 114 academic staff from Curtin University in Perth, Australia. An online survey was conducted to gather data on the target variables. A moderated hierarchical regression indicated that the combined model accounted for a significant 11.90% of the variance in email stress (p = .008, f² = .135). Worry individually accounted for a significant proportion of the variance (p = .010, f² = .06, 95% CI [.028, .202]). Email volume also significantly predicted email stress (p = .00, f² = .057, 95% CI [.011, .079]). Email management did not moderate the email volume and stress relationship. The findings suggest that email stress is impacting upon academic teaching staff and that research on mitigating this stress needs to be undertaken.     

Exposure to and effects of glare from high mast lighting on workers at a timber terminal

High mast floodlighting at outdoor workplaces has economic advantages but suffers from shortcomings such as glare. This study was made to collect and evaluate data from a situation with glare from a physical and occupational health standpoint. When unloading timber, the worker's gaze is frequently directed upward, whereas conventional glare indexes for luminaires assume the gaze is diagonally downwards. It was found that reduced visual acuity could cause difficulty in normal working routines.     

Stressful jobs and non-stressful jobs: a cluster analysis of office jobs

The purpose of the study was to determine if office jobs could be characterized by a small number of combinations of stressors that could be related to job-title information and self-report of psychological strain. Two-hundred-and-sixty-two office workers from three public service organizations provided data on nine job stressors and seven indicators of psychological strain. Using cluster analysis on the nine stressors, office jobs were classified into three clusters. The first cluster included jobs with high skill utilization, task clarity, job control and social support and low future ambiguity, but also high on job demands such as quantitative workload, attention and work pressure. The second cluster included jobs with high demands and future ambiguity and low skill utilization, task clarity, job control and social support. The third cluster was intermediary between the first two clusters. The three clusters were related to job-title information. The second cluster was the highest on a range of psychological strain indicators, while the other two clusters were high on certain strain indicators but low on others. The study showed that office jobs could be characterized by a small number of combinations of stressors that were related to job-title information and psychological strain.     

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.     

Upper trapezius muscle activity in healthy office workers: reliability and sensitivity of occupational exposure measures to differences in sex and hand dominance

Patterns of cervical muscle activity may contribute to overuse injuries in office workers. The purpose of this investigation was to characterise patterns of upper trapezius muscle activity in pain-free office workers using traditional occupational exposure measures and a modified Active Amplitude Probability Distribution Function (APDF), which considers only periods of active muscle contraction. Bilateral trapezius muscle activity was recorded in 77 pain-free office workers for 1–2 full days in their natural work environment. Mean amplitude, gap frequency, muscular rest and Traditional and Active APDF amplitudes were calculated. All measures demonstrated fair to substantial reliability. Dominant muscles demonstrated higher amplitudes of activity and less muscular rest compared to non-dominant, and women demonstrated less muscular rest with no significant difference in amplitude assessed by Active APDF compared to men. These findings provide normative data to identify atypical motor patterns that may contribute to persistence or recurrence of neck pain in office workers.

Practitioner Summary: Upper trapezius muscle activity was characterised in a large cohort of pain-free workers using electromyographic recordings from office environments. Dominant muscles demonstrated higher activity and less rest than non-dominant, and women demonstrated less rest than men. Results may be used to identify atypical trapezius muscle activity in office workers.