Acute effects of firefighting on arterial stiffness and blood flow

Physiological Stress Responses to a Live-Fire Training Evolution in Career Structural Firefighters

OBJECTIVE

This study assessed firefighters' physiological stress response to a live fire training evolution (LFTE).

METHODS

Seventy-six ( n = 76) firefighters completed an LFTE. Salivary samples were collected pre-, immediately post, and 30-min post-LFTE and analyzed for α-amylase (AA), cortisol (CORT), and secretory immunoglobulin-A (SIgA).

RESULTS

Concentrations of AA, CORT, and SIgA were elevated immediately post LFTE versus pre (P<0.001) and 30-min post (P<0.001). Cohen's d effect size comparing pre and immediately-post means were 0.83, 0.77, and 0.61 for AA, CORT, and SIgA and were 0.54, 0.44, and 0.69 for AA, CORT, and SIgA, comparing immediately-post and 30-min post, respectively.

CONCLUSIONS

These data demonstrate the stress response and activation of the hypothalamic-pituitary-adrenal/sympathetic-adreno-medullar axis and immune system immediately after real-world firefighting operations. Future work is needed to understand the impact of elevated stress biomarkers on firefighter performance and disease risk.

Dynamic molecular choreography induced by acute heat exposure in human males: a longitudinal multi-omics profiling study

Introduction

Extreme heat events caused by occupational exposure and heat waves are becoming more common. However, the molecular changes underlying the response to heat exposure in humans remain to be elucidated.

Methods

This study used longitudinal multi-omics profiling to assess the impact of acute heat exposure (50°C for 30 min) in 24 subjects from a mine rescue team. Intravenous blood samples were collected before acute heat exposure (baseline) and at 5 min, 30 min, 1 h, and 24 h after acute heat exposure (recovery). In-depth multi-omics profiling was performed on each sample, including plasma proteomics (untargeted) and metabolomics (untargeted).

Results

After data curation and annotation, the final dataset contained 2,473 analytes, including 478 proteins and 1995 metabolites. Time-series analysis unveiled an orchestrated molecular choreography of changes involving the immune response, coagulation, acid-base balance, oxidative stress, cytoskeleton, and energy metabolism. Further analysis through protein-protein interactions and network analysis revealed potential regulators of acute heat exposure. Moreover, novel blood-based analytes that predicted change in cardiopulmonary function after acute heat exposure were identified.

Conclusion

This study provided a comprehensive investigation of the dynamic molecular changes that underlie the complex physiological processes that occur in human males who undergo heat exposure. Our findings will help health impact assessment of extreme high temperature and inspire future mechanistic and clinical studies.

Overexertion and heat stress in the fire service: a new conceptual framework

From the year 2000, the United States Fire Administration (USFA) has been recording all line-of-duty deaths in the fire service. Stress or overexertion caused 1096 out of 2598 total line-of-duty deaths in the United States from 2000 to 2021. Those deaths due to stress or overexertion were further classified as myocardial infarction (90%), cerebrovascular accident (6.8%), other (2.6%), and heat exhaustion (0.6%). Environmental heat exposure is a concern in firefighting, as firefighters work in extreme conditions, such as high ambient temperatures, while wearing protective clothing. Heat stress is not only hazardous to the cardiovascular system, but may accentuate muscle fatigue and overexertion. In addition, overexertion itself is related to increased incidence of musculoskeletal injuries, usually to the lower extremities. Further, there is a strong physiological mechanistic link to suggest that the increased occupational heat exposure and thermoregulatory strain firefighters experience may be a stressor that increases the risk of injuries. This commentary hopes to show the need for further research on the effects of occupational exposures and physiological strain in the fire service.

Comparison of Acute Arterial Responses Following a Rescue Simulation and Maximal Exercise in Professional Firefighters

Cardiovascular events are the leading cause of on-duty deaths among firefighters. Screening firefighters for risk of sudden cardiac event is a critical element of a comprehensive medical program. Although intense physical exertion has been shown to trigger sudden cardiac events in the general population, it is unclear how hemodynamic responses following clinical exercise testing compare to that of performing firefighting tasks in personal protective equipment. Therefore, the purpose of this study was to compare hemodynamic responses following rescue simulation (RS) and maximal exercise in firefighters. This was a cross-over repeated measures study. Thirty-eight professional firefighters (31.8 ± 5.2 yr; VO2peak: 57.9 mL/kg/min) completed a maximal aerobic exercise test (MAET) and an RS. Pulse wave velocity (PWV), pulse pressure (PP), and brachial and central mean arterial pressure (MAP) were measured before and 5 and 15 min post-exercise. The findings indicated that femoral PWV decreased after MAET and RS at both time points (p < 0.005). No significant differences were found in aortic and carotid PWV over time or between conditions (p ≥ 0.05). Significant increases in brachial and central PP and MAP were noted 5 min post-MAET and RS (p = 0.004). In conclusion, the present study demonstrated that peripheral arterial stiffness (AS) decreased in firefighters following both conditions, with no differences in central AS. Our findings provide valuable information on hemodynamic responses similar between RS and MAET, and are important for controlling CVD risk and the AS response.

Heart rate dynamics during a simulated fireground test: The influence of physical characteristics and fitness1

BACKGROUND

Firefighting is a physiologically demanding occupation and there is a need to evaluate physical and fitness characteristics that are related to attenuated physiological stress during fireground tasks. Previous studies have not measured associations between heart rate responses during simulated fireground tasks with a standardized work rate.

OBJECTIVE

The purpose of this study was to examine associations between heart rate during a standardized pace simulated fireground test (SFGT) and heart rate recovery and variability following the SFGT. In addition, this study sought to evaluate associations between heart rate measures versus physical and fitness characteristics in structural firefighter recruits.

METHODS

Twenty-one fire academy recruits performed a standardized pace SFGT while mean heart rate reserve (HRRes) during the SFGT, change in heart rate variability from rest to post-SFGT (LnRMSSDRest-Post), and 60-second post-SFGT heart rate recovery (HRR60) were measured. Regression analyses were conducted between HRRes, LnRMSSDRest-Post and HRR60 and between heart rate measures versus physical and fitness characteristics while accounting for differences in SFGT completion time.

RESULTS

HRRes was associated with LnRMSSDRest-Post, but not HRR60. Height and pull-ups explained most of the variance in HRRes, height explained most of the variance in LnRMSSDRest-Post and push-ups and 1.5-mile run explained most of the variance in HRR60.

CONCLUSION

Greater cardiovascular stress during fireground tasks is associated with greater depression of post-SFGT heart rate variability, but not heart rate recovery. Physical and fitness characteristics are important to consider in relation to firefighters' ability to cope with physical stress on the fireground.

Blood Pressure Responses in Firefighters: A Review

Blood pressure (BP) responses are controlled by various factors and understanding how BP changes is important to occupational health. This paper presents a review of the literature that reports BP responses in the firefighter population. Hypertension is one of the main risk factors underlying the pathophysiology of cardiovascular disease (CVD), and cardiac incidents remain the leading cause of line-of-duty deaths in firefighters. Risk factors for line-of-duty deaths include obesity, previous or underlying heart disease, and hypertension. The occupation of firefighting is one of the most hazardous and dangerous jobs, yet over 50 % of firefighters are volunteers. Tactical operations and the hazardous nature of firefighting are exposures that influence stress responses and, therefore, affect BP. In fact, hypertension in firefighters often remains undocumented or undiagnosed. CVD risk and elevated BP in tactical populations, like firefighters, maybe a combination of physical and emotional stress due to the nature of the job. Cross-sectional studies have reported that firefighters have higher levels of BP and higher rates of hypertension compared to civilians. Interestingly, there is a limited amount of research that reports BP values before and after firefighting- related activities, and very few studies on interventional changes in BP. Here, we synthesize the literature on firefighting and provide a summary of the studies that report pre- and post- BP levels that relate to CVD risk factors, occupational factors, firefighting activities, and the data on exercise training and BP. More studies are needed that examine BP in firefighters and report on the changes in BP with occupational activities.

International society of sports nutrition position stand: tactical athlete nutrition

This position stand aims to provide an evidence-based summary of the energy and nutritional demands of tactical athletes to promote optimal health and performance while keeping in mind the unique challenges faced due to work schedules, job demands, and austere environments. After a critical analysis of the literature, the following nutritional guidelines represent the position of the International Society of Sports Nutrition (ISSN).

General Recommendations

Nutritional considerations should include the provision and timing of adequate calories, macronutrients, and fluid to meet daily needs as well as strategic nutritional supplementation to improve physical, cognitive, and occupational performance outcomes; reduce risk of injury, obesity, and cardiometabolic disease; reduce the potential for a fatal mistake; and promote occupational readiness.

Military Recommendations

Energy demands should be met by utilizing the Military Dietary Reference Intakes (MDRIs) established and codified in Army Regulation 40-25. Although research is somewhat limited, military personnel may also benefit from caffeine, creatine monohydrate, essential amino acids, protein, omega-3-fatty acids, beta-alanine, and L-tyrosine supplementation, especially during high-stress conditions.

First Responder Recommendations

Specific energy needs are unknown and may vary depending on occupation-specific tasks. It is likely the general caloric intake and macronutrient guidelines for recreational athletes or the Acceptable Macronutrient Distribution Ranges for the general healthy adult population may benefit first responders. Strategies such as implementing wellness policies, setting up supportive food environments, encouraging healthier food systems, and using community resources to offer evidence-based nutrition classes are inexpensive and potentially meaningful ways to improve physical activity and diet habits. The following provides a more detailed overview of the literature and recommendations for these populations.

Association Between Atrial Fibrillation and Occupational Exposure in Firefighters Based on Self-Reported Survey Data

Background Exposure to inhaled smoke, pollutants, volatile organic compounds, and polycyclic aromatic hydrocarbons in the firefighting environment has been associated with detrimental respiratory and cardiovascular effects, making firefighters a unique population with both personal and occupational risk factors for cardiovascular disease. Some of these exposures are also associated with development of atrial fibrillation. We aimed to study the association of atrial fibrillation and occupational exposure in firefighters. Methods and Results A cross-sectional survey was conducted between October 2018 and December 2019. Data were gathered electronically and stored in a secure REDCap database through Louisiana State University Health Shreveport. Firefighters who were members of at least 1 of 5 preselected professional organizations were surveyed via electronic links distributed by the organizations. The survey queried the number of fires fought per year as a measure of occupational exposure, as well as self-reported cardiovascular disease. A total of 10 860 active firefighters completed the survey, of whom 93.5% were men and 95.5% were aged ≤60 years. Firefighters who fought a higher number of fires per year had a significantly higher prevalence of atrial fibrillation (0-5 fires per year 2%, 6-10 fires per year 2.3%, 11-20 fires per year 2.7%, 21-30 fires per year 3%, 31 or more fires per year 4.5%; P<0.001). Multivariable logistic regression showed that a higher number of fires fought per year was associated with an increased risk of atrial fibrillation (odds ratio 1.14 [95% CI, 1.04-1.25]; P=0.006). Conclusions Firefighters may have an increased risk of atrial fibrillation associated with the number of fires they fight per year. Further clinical and translational studies are needed to explore causation and mechanisms.

Vitamin C May Improve Left Ventricular Ejection Fraction: A Meta-Analysis

Background

Vitamin C deprivation can lead to fatigue, dyspnea, oedema and chest pain, which are also symptoms of heart failure (HF). In animal studies vitamin C has improved contractility and mechanical efficiency of the heart. Compared with healthy people, patients with HF have lower vitamin C levels, which are not explained by differences in dietary intake levels, and more severe HF seems to be associated with lower plasma vitamin C levels. This meta-analysis looks at the effect of vitamin C on left ventricular ejection fraction (LVEF).

Methods

We searched for trials reporting the effects of vitamin C on LVEF. We assessed the quality of the trials, and pooled selected trials using the inverse variance, fixed effect options. We used meta-regression to examine the association between the effect of vitamin C on LVEF level and the baseline LVEF level.

Results

We identified 15 trials, three of which were excluded from our meta-analysis. In six cardiac trials with 246 patients, vitamin C increased LVEF on average by 12.0% (95% CI 8.1–15.9%; P < 0.001). In six non-cardiac trials including 177 participants, vitamin C increased LVEF on average by 5.3% (95% CI 2.0–8.5%; P = 0.001). In meta-regression analysis we found that the effect of vitamin C was larger in trials with the lowest baseline LVEF levels with P = 0.001 for the test of slope. The meta-regression line crossed the null effect level at a baseline LVEF level close to 70%, with progressively greater benefit from vitamin C with lower LVEF levels. Some of the included trials had methodological limitations. In a sensitivity analysis including only the four most methodologically sound cardiac trials, the effect of vitamin C was not substantially changed.

Conclusions

In this meta-analysis, vitamin C increased LVEF in both cardiac and non-cardiac patients, with a strong negative association between the size of the vitamin C effect and the baseline LVEF. Further research on vitamin C and HF should be carried out, particularly in patients who have low LVEF together with low vitamin C intake or low plasma levels. Different dosages and different routes of administration should be compared.

Effect of live-fire training on ventricular-vascular coupling

INTRODUCTION

Cardiovascular events are a leading cause of firefighter duty-related death, with the greatest risk occurring during or shortly after fire suppression activity. Increased cardiovascular risk potentially manifests from detrimental changes in ventricular function, vascular load, and their interaction, described as ventricular-vascular coupling.

PURPOSE

To determine the effect of live-fire training on ventricular-vascular coupling.

METHODS

Sixty-eight male (28 [Formula: see text] 7 years, 26.9 [Formula: see text] 3.9 kg/m²) and fifteen female (36 [Formula: see text] 8 years, 24.3 [Formula: see text] 3.9 kg/m²) firefighters completed hemodynamic and cardiac measures before and after 3 h of intermittent live-fire training. Left ventricular function was assessed as ejection fraction (EF) and ventricular elastance (E_LV: end systolic pressure [ESP]/end systolic volume) via echocardiography and applanation tonometry-estimated ESP. Vascular load was assessed as arterial elastance (E_A: ESP/stroke volume [SV]). Ventricular-vascular coupling (VVC) was quantified as the ratio of E_A to E_LV and indexed to body surface area (E_AI, E_LVI).

RESULTS

Following firefighting EF decreased (p < 0.01) with no change in E_LVI (p = 0.34). SV decreased (p < 0.01) with no change in ESP (p = 0.09), driving a significant increase in E_AI (p < 0.01). These changes resulted in a significant increase in the VVC ratio (p < 0.01).

CONCLUSION

The findings suggest that firefighting does not alter ventricular elastance but increases arterial elastance in healthy firefighters, resulting in a mismatch between ventricular and vascular systems. This increase in ventricular-vascular coupling ratio and concomitant reduction in ventricular systolic function may contribute to increased cardiovascular risk following live firefighting.

Predictors of Arterial Stiffness in Law Enforcement Officers

BACKGROUND

Compare arterial stiffness among law enforcement officers (LEOs) versus general population normative values and identify predictors of arterial stiffness in LEOs.

METHODS

Seventy male LEOs (age: 24-54 years) completed body composition, blood pressures, physical activity level, and carotid-femoral pulse wave velocity (cfPWV) measurements. T-tests and regression analyses were utilized to compare LEO data to normative data and predict cfPWV, respectively.

RESULTS

Compared to similar age strata within the general population, cfPWV was lower among LEO's under 30-years (mean difference = -0.6 m·s^-1), but higher among LEOs 50-55-years (mean difference = 1.1 m·s^-1). Utilizing regression, age, relative body fat, and diastolic blood pressure explained the greatest variance in LEO's cfPWV (adj. R² = 0.56, p < 0.001).

CONCLUSION

This investigation demonstrated that arterial stiffness may progress more rapidly in LEOs and LEOs' relative body fat and blood pressure may primarily affect arterial stiffness and risk of CVD.

Cardiometabolic health among United States firefighters by age

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Cardiometabolic health in male firefighters was lowest among 45–50 year olds.

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Cardiometabolic health continually decreased with age among female firefighters.

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Firefighters have similar or better cardiometabolic health than the US population.

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Cardiometabolic risk factors were prevalent in firefighters and the US population.

Firefighting is strenuous work that results in considerable cardiovascular strain. Sudden cardiac events are the leading cause of duty-related death in the fire service. This cross-sectional study examined cardiometabolic measures and prevalence of risk factors in firefighters by age and sex and compare these data to the general population. Data obtained at medical exams (2015–2018) from 4279 male and 234 female career firefighters at four occupational health clinics in the United States were analyzed. Estimates for the general population were obtained using the 2015–16 National Health and Nutrition Examination Survey fasting subsample. Linear regression models stratified by sex with age modelled as a continuous variable were used to examine general trends. Point estimates across age groups (20–29, 30–39, 40–49, and 50–59 year olds) for cardiometabolic measures were reported. Among the total sample, 36% were obese and 25% had low HDL cholesterol. Females had significantly lower body mass index (BMI), LDL cholesterol, triglycerides and blood glucose than males. A significant quadratic relationship of age with BMI, total cholesterol, LDL cholesterol, and triglycerides was found in males with increasing values peaking between 45 and 50 years. Total cholesterol and LDL cholesterol increased with age among females. Blood glucose increased with age in both sexes. Firefighters had similar or better cardiometabolic health profiles than the US general population; however, both samples had a concerning prevalence of cardiometabolic risk factors among individuals ≥ 40 years of age. Health professionals and fire service members alike should consider prevention efforts among young firefighters and better treatment among older firefighters.

Low testosterone and cardiometabolic risks in a real-world study of US male firefighters

Low serum total testosterone (TT) is associated with increased cardiovascular risk and metabolic derangements, with fatty liver (FL) emerging as an additional cardiometabolic threat. We investigated the associations between TT and cardiometabolic (CM) health in 298 US male firefighters. Cross-sectional data from occupational health examination were analyzed. TT was categorized as low (< 264 ng/dL), borderline (264-399 ng/dL), and reference (400-916 ng/dL). Conventional CM risk factors were compared among TT categories, and between firefighters with and without FL. 81% of firefighters were obese/overweight; almost 40% had FL. In the low-TT group, only 3.1% had normal BMI, while 78.1% had FL. The low-TT group had a worse CM profile, independently of age and BMI, and a fourfold higher adjusted odds of having FL. FL was associated with lower TT, regardless of age, BMI and HbA1c. Having a FL, HbA1c ≥ 5.7% or triglycerides ≥ 150 mg/dL increased the odds for low-TT by 4.1, 2.7 and 6.6 times, respectively. These real-world data reveal strong associations between low-TT and CM risk factors and support a call for action towards screening for low-TT and FL, regardless of age, BMI or dysmetabolic conditions in firefighters. Recognizing cardiometabolic risks in firefighters provides an opportunity to lessen cardiovascular diseases burden.

Cardiovascular Disease Risk Factors by BMI and Age in United States Firefighters

OBJECTIVE

This study examined cardiovascular disease risk factors by BMI category in firefighters, the association of BMI and age with risk factor prevalence, and the prevalence of risk factors by BMI category within age groups.

METHODS

Cardiovascular measures from the medical evaluations of 4,453 firefighters, performed between 2015 and 2018 at four occupational health clinics in the United States (South-West Cohort, Mid-Atlantic Cohort, South-East Cohort, and Mid-West Cohort), were analyzed cross-sectionally by BMI and age categories.

RESULTS

Among female firefighters with normal weight, 25% had high blood pressure, 8% had low high-density lipoprotein cholesterol, and 0% had high glucose, whereas the prevalence in female firefighters with obesity was 57%, 45%, and 11%, respectively. Among male firefighters, there were independent and significant associations of BMI and age for the prevalence of high blood pressure, high cholesterol, high triglycerides, and high glucose. Higher BMI category was associated with a higher prevalence of high blood pressure, high triglycerides, and low high-density lipoprotein cholesterol within all age groups and with a higher prevalence of high glucose and high cholesterol within ages 40 to 49 and 50 to 59 years.

CONCLUSIONS

An increasing prevalence of risk factors with older age and higher BMI suggests that preventive strategies should be initiated in younger firefighters and aggressively promoted or mandated throughout firefighters' careers.

Firefighter hemodynamic responses to different fire training environments

Firefighting is associated with an increased risk for a cardiovascular (CV) event, likely due to increased CV strain. The increase in CV strain during firefighting can be attributed to the interaction of several factors such as the strenuous physical demand, sympathetic nervous system activation, increased thermal burden, and the environmental exposure to smoke pollutants. Characterizing the impact of varying thermal burden and pollutant exposure on hemodynamics may help understand the CV burden experienced during firefighting. The purpose of this study was to examine the hemodynamic response of firefighters to training environments created by pallets and straw; oriented strand board (OSB); or simulated fire/smoke (fog). Twenty-three firefighters had brachial blood pressure measured and central blood pressure and hemodynamics estimated from the pressure waveform at baseline, and immediately and 30 minutes after each scenario. The training environment did not influence the hemodynamic response over time (interaction, p > 0.05); however, OSB scenarios resulted in higher pulse wave velocity and blood pressure (environment, p < 0.05). In conclusion, conducting OSB training scenarios appears to create the largest arterial burden in firefighters compared to other scenarios in this study. Environmental thermal burden in combination with the strenuous exercise, and psychological and environmental stress placed on firefighters should be considered when designing fire training scenarios and evaluating CV risk.

Firefighting Induces Acute Inflammatory Responses that are not Relieved by Aspirin in Older Firefighters

OBJECTIVE

Sudden cardiac events account for 40% to 50% of firefighter line-of-duty deaths. Inflammatory proteins are strong biomarkers of cardiovascular inflammation. The present study investigated the effects of aspirin supplementation on inflammatory biomarkers following firefighting.

METHODS

Using a randomized, placebo-controlled, double-blind crossover design, 24 male firefighters (48.2 ± 5.9 years) were allocated into four conditions: acute (81 mg; single-dose) aspirin and placebo supplementation, and chronic (81 mg; 14 days) aspirin and placebo supplementation. Inflammatory proteins [interleukin (IL)-6, C-reactive protein (CRP), intracellular adhesion molecule (ICAM)-1, P-selectin, matrix metalloproteinase-9 (MMP-9)] and antioxidant potential [total antioxidant capacity (TAC)] were measured pre- and post-structural firefighting drills.

RESULTS

Firefighting activities significantly increased IL-6, MMP-9, and P-Selectin; however, no changes in TAC and ICAM-1 were detected. Neither acute nor chronic aspirin supplementation attenuated this inflammatory response.

CONCLUSION

Firefighting significantly increases inflammatory biomarkers and neither acute nor chronic low-dose aspirin mitigates this response.

Extreme occupational heat exposure is associated with elevated haematological and inflammatory markers in Fire Service Instructors

NEW FINDINGS

What is the central question of this study? Fire service instructors are frequently exposed to live fire scenarios, representing the most extreme chronic occupational heat exposure. These individuals report a series of unique health issues. We sought to identify whether the number of exposures completed was associated with inflammatory and immunological markers and symptoms of ill health. What is the main finding and its importance? Fire service instructors exhibit greater levels of inflammatory markers in comparison to firefighters. The number of exposures to fire is positively related to the prevalence of ill health and inflammation. Implementation of a proposed limit of nine exposures per month might be appropriate to minimize health issues.

ABSTRACT

Fire Service Instructors (FSIs) experience ∼10 times more fire exposures than firefighters (FFs), and the increased physiological stress from this potentially puts them at risk of ill health and future cardiac events. The aim of the study was to establish whether FSIs exhibit elevated biomarkers associated with cardiac event risk, identify whether FSIs experience systemic inflammation linked to the frequency of fire exposure and evaluate a proposed exposure limit of nine exposures per month. Blood samples were collected from 110 Fire Service personnel (mean ± SD, age,44 ± 7 years; height, 178.1 ± 7.1 cm; and body mass, 84.3 ± 12.0 kg; FSIs n = 53 and FFs n = 57) for biomarker analysis. Work history details were collected from all participants. Participants with biomarker concentrations above healthy reference ranges were classified as being 'at risk'. The neutrophil-to-lymphocyte ratio, platelet count, cardiac troponin T, interleukin (IL)-6, IL-1β, C-reactive protein and immunoglobulin G were greater in FSIs than in FFs (P < 0.05). Multiple regression analysis revealed that 18.8% of IL-6, 24.9% of IL-1β, 29.2% of C-reactive protein and 10.9% of immunoglobulin G variance could be explained by the number of exposures to heat per month. Odds ratios revealed that those FSIs above the nine per month exposure limit were six to 12 times more likely to be classified as 'at risk' and were 16 times more likely to experience symptoms of ill health. Increased cytokine levels suggest that FSIs experience systemic inflammation, which is related to symptoms of ill health. We propose that an exposure limit could reduce the prevalence of these biomarker risk factors and ill health.

Physiologic strain of SCBA confidence course training compared to circuit training and live-fire training

Firefighting is a dangerous occupation and even training carries substantial risks. Self-contained breathing apparatus confidence courses (SCBACC) are a common type of training.

PURPOSE

Compare the physiological strain of SCBACC to live-fire training (LFT) and circuit training (CT) among academy cadets.

METHODS

Cadets wore physiologic status monitors to assess heart rate (HR) and estimated core temperature (ECT) during CT, LFT, and SCBACC of similar duration (33-38 min).

RESULTS

Data from 52 cadet firefighters (28 ± 4 yrs old) were analyzed. ECT (38.6 ± 0.4 vs 39.3 ± 0.7 vs. 39.3 ± 0.6ᵒC), peak HR (182.6 ± 9.1 vs. 192.7 ± 9.5 vs 195.9 ± 9.6 bpm), and age-predicted maximal HR (APMHR%; 94.6 ± 4.6 vs 99.9 ± 4.9 vs. 101.5 ± 4.8%) were significantly (p < 0.05) lower for CT than SCBACC and LFT, respectively.

CONCLUSIONS

SCBACC produced physiological strain greater than CT and similar to LFT. SCBACC resulted in sustained HR at 100% of age-predicted maximal values, a peak ECT of 39.3 °C, and should be considered as physiologically stressful as LFT.

The Relation of Emergency Duties to Cardiac Death Among US Firefighters

Sudden cardiac death accounted for 42% of all firefighter duty-related fatalities over the last decade. This retrospective study analyzed available medical examiner records for duty-related firefighter fatalities among male firefighters 18 to 65 years of age that occurred between 1999 and 2014 and reported the pathoanatomic substrate for cardiac-related fatalities. Odds of duty-related cardiac death during specific duties compared with fire station duties were calculated by pathoanatomic substrate. There were 285 cardiac fatalities. Of fatalities, 80% had evidence at autopsy of coronary heart disease (CHD) and increased heart size (cardiomegaly and/or left ventricular hypertrophy). CHD alone, cardiomegaly or left ventricular hypertrophy, and causes other than CHD or increased heart size were identified in 7.7%, 6.0%, and 6.7% of fatalities, respectively. The largest proportion of deaths occurred during fire suppression (33%), although only 1% of annual occupational time was estimated to be spent performing this duty. For deaths attributed to CHD and increased heart size, fire suppression, alarm response, and physical training were associated with approximately a 112-fold, eightfold, and sevenfold increased risk of cardiac death, respectively, compared with station duties. In conclusion, the majority of firefighters who suffered a duty-related cardiac death had CHD and increased heart size, which was associated with a markedly increased risk of death during fire suppression compared with station duties. Targeted occupational medical screening for CHD and increased heart size may reduce duty-related cardiac deaths among firefighters.

The effect of acute maximal exercise on postexercise hemodynamics and central arterial stiffness in obese and normal-weight individuals

Central arterial stiffness is associated with incident hypertension and negative cardiovascular outcomes. Obese individuals have higher central blood pressure (BP) and central arterial stiffness than their normal‐weight counterparts, but it is unclear whether obesity also affects hemodynamics and central arterial stiffness after maximal exercise. We evaluated central hemodynamics and arterial stiffness during recovery from acute maximal aerobic exercise in obese and normal‐weight individuals. Forty‐six normal‐weight and twenty‐one obese individuals underwent measurements of central BP and central arterial stiffness at rest and 15 and 30 min following acute maximal exercise. Central BP and normalized augmentation index (AIx@75) were derived from radial artery applanation tonometry, and central arterial stiffness was obtained via carotid‐femoral pulse wave velocity (cPWV) and corrected for central mean arterial pressure (cPWV/cMAP). Central arterial stiffness increased in obese individuals but decreased in normal‐weight individuals following acute maximal exercise, after adjusting for fitness. Obese individuals also exhibited an overall higher central BP (P < 0.05), with no exercise effect. The increase in heart rate was greater in obese versus normal‐weight individuals following exercise (P < 0.05), but there was no group differences or exercise effect for AIx@75. In conclusion, obese (but not normal‐weight) individuals increased central arterial stiffness following acute maximal exercise. An assessment of arterial stiffness response to acute exercise may serve a useful detection tool for subclinical vascular dysfunction.

Cardiovascular health effects following exposure of human volunteers during fire extinction exercises

BACKGROUND

Firefighters have increased risk of cardiovascular disease and of sudden death from coronary heart disease on duty while suppressing fires. This study investigated the effect of firefighting activities, using appropriate personal protective equipment (PPE), on biomarkers of cardiovascular effects in young conscripts training to become firefighters.

METHODS

Healthy conscripts (n = 43) who participated in a rescue educational course for firefighting were enrolled in the study. The exposure period consisted of a three-day training course where the conscripts participated in various firefighting exercises in a constructed firehouse and flashover container. The subjects were instructed to extinguish fires of either wood or wood with electrical cords and mattresses. The exposure to particulate matter (PM) was assessed at various locations and personal exposure was assessed by portable PM samplers and urinary excretion of 1-hydroxypyrene. Cardiovascular measurements included microvascular function and heart rate variability (HRV).

RESULTS

The subjects were primarily exposed to PM in bystander positions, whereas self-contained breathing apparatus effectively abolished pulmonary exposure. Firefighting training was associated with elevated urinary excretion of 1-hydroxypyrene (105%, 95% CI: 52; 157%), increased body temperature, decreased microvascular function (-18%, 95% CI: -26; -9%) and altered HRV. There was no difference in cardiovascular measurements for the two types of fires.

CONCLUSION

Observations from this fire extinction training show that PM exposure mainly occurs in situations where firefighters removed the self-contained breathing apparatus. Altered cardiovascular disease endpoints after the firefighting exercise period were most likely due to complex effects from PM exposure, physical exhaustion and increased core body temperature.

Wood smoke exposure of Portuguese wildland firefighters: DNA and oxidative damage evaluation

Portugal is among the European Union countries most devastated by forest fires each year. In the last three decades, more than 3.8 million hectares of forest were burned. Wildland firefighters are exposed to a variety of hazards, including many toxic combustion products that may lead to deleterious health effects. Epidemiological studies showed a positive association between firefighting and several chronic diseases, including cancer. Results from biomonitoring studies in firefighters, particularly concerning genotoxicity evaluation, constitute a valuable tool for investigating important occupational hazards. Thus, the aim of this study was to assess genotoxicity in a group of wildland firefighters using the comet assay for DNA damage and oxidative stress. Both parameters were increased in firefighters compared to controls, but significance was only found for basal DNA damage. No significant influence was found regarding major confounding variables on the genotoxic endpoints studied, with the exception of age. Data obtained provide preliminary information on human health effects of wildland firefighting exposure at genetic and molecular levels. These findings may also provide new important data to serve as public awareness to the potential adverse health risks involving wildland firefighting. Implementation of security and hygiene measures in this sector as well as good practices campaigns may be crucial to decrease risk.

Fire Simulation and Cardiovascular Health in Firefighters

BACKGROUND

Rates of myocardial infarction in firefighters are increased during fire suppression duties, and are likely to reflect a combination of factors including extreme physical exertion and heat exposure. We assessed the effects of simulated fire suppression on measures of cardiovascular health in healthy firefighters.

METHODS

In an open-label randomized crossover study, 19 healthy firefighters (age, 41±7 years; 16 males) performed a standardized training exercise in a fire simulation facility or light duties for 20 minutes. After each exposure, ex vivo thrombus formation, fibrinolysis, platelet activation, and forearm blood flow in response to intra-arterial infusions of endothelial-dependent and -independent vasodilators were measured.

RESULTS

After fire simulation training, core temperature increased (1.0±0.1°C) and weight reduced (0.46±0.14 kg, P<0.001 for both). In comparison with control, exposure to fire simulation increased thrombus formation under low-shear (73±14%) and high-shear (66±14%) conditions (P<0.001 for both) and increased platelet-monocyte binding (7±10%, P=0.03). There was a dose-dependent increase in forearm blood flow with all vasodilators (P<0.001), which was attenuated by fire simulation in response to acetylcholine (P=0.01) and sodium nitroprusside (P=0.004). This was associated with a rise in fibrinolytic capacity, asymptomatic myocardial ischemia, and an increase in plasma cardiac troponin I concentrations (1.4 [0.8-2.5] versus 3.0 [1.7-6.4] ng/L, P=0.010).

CONCLUSIONS

Exposure to extreme heat and physical exertion during fire suppression activates platelets, increases thrombus formation, impairs vascular function, and promotes myocardial ischemia and injury in healthy firefighters. Our findings provide pathogenic mechanisms to explain the association between fire suppression activity and acute myocardial infarction in firefighters.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01812317.

Exercise-induced heat stress disrupts the shear-dilatory relationship

NEW FINDINGS

What is the central question of this study? Although heat stress is known to increase cardiovascular strain, no study, to date, had explored the potential impact of exercise-induced heat stress on vascular function. What is the main finding and its importance? We found that acute exercise tended to reduce flow-mediated dilatation (FMD), owing in part to reduced reactive hyperaemia/shear stimulus; thus, when FMD is normalized to shear no postexercise deficit exists. Exercise-induced heat stress increased reactive hyperaemia, shear rate, coupled with a sustained FMD postexercise, suggests that exercise-induced heat stress increases the amount of shear stimulus to elicit a similar response, indicating reduced vascular responsiveness, or reserve, which might increase cardiovascular susceptibility. Heat stress increases cardiovascular strain and is of particular concern in occupations, such as firefighting, in which individuals are required to perform strenuous work while wearing personal protective equipment. Sudden cardiac events are associated with strenuous activity and are the leading cause of duty-related death among firefighters, accounting for ∼50% of duty-related fatalities per year. Understanding the acute effects of exercise-induced heat stress (EIHS) on vascular endothelial function may provide insight into the mechanisms precipitating acute coronary events in firefighters. The purpose of this study, therefore, was to determine the effects of EIHS on vascular endothelial function. Using a balanced crossover design, 12 healthy men performed 100 min of moderate-intensity, intermittent exercise with and without EIHS (personal protective equipment or cooling vest, respectively). Measurements of flow-mediated dilatation (FMD), reactive hyperaemia and shear rate area under the curve (SR_AUC ) were performed pre- and postexercise. During EIHS, core temperature was significantly higher (38 ± 0.1 versus 37 ± 0.1°C). Postexercise FMD tended to be suppressed in both conditions, but was not different from pre-exercise. Reactive hyperaemia was reduced after no-EIHS but increased after EIHS. Thus, normalizing FMD to the shear stimulus (FMD/SR_AUC ) revealed a significant reduction in FMD after EIHS only (pre-exercise 0.15 ± 0.04 and 0.13 ± 0.02 s^-1 versus postexercise, 0.13 ± 0.02 and 0.06 ± 0.02 s^-1 , no-EIHS and EIHS, respectively). We conclude that moderate heat stress superimposed on moderate-intensity exercise resulted in reduced vascular endothelial function. This heat stress-induced alteration in the shear-dilatory relationship may relate to the increased risk of acute coronary events associated with activities that combine physical exertion and heat stress (i.e. firefighting).

Features of the non-contact carotid pressure waveform: Cardiac and vascular dynamics during rebreathing

This report amplifies and extends prior descriptions of the use of laser Doppler vibrometry (LDV) as a method for assessing cardiovascular activity, on a non-contact basis. A rebreathing task (n = 35 healthy individuals) was used to elicit multiple effects associated with changes in autonomic drive as well as blood gases including hypercapnia. The LDV pulse was obtained from two sites overlying the carotid artery, separated by 40 mm. A robust pulse signal was obtained from both sites, in accord with the well-described changes in carotid diameter over the blood pressure cycle. Emphasis was placed on extracting timing measures from the LDV pulse, which could serve as surrogate measures of pulse wave velocity (PWV) and the associated arterial stiffness. For validation purposes, a standard measure of pulse transit time (PTT) to the radial artery was obtained using a tonometric sensor. Two key measures of timing were extracted from the LDV pulse. One involved the transit time along the 40 mm distance separating the two LDV measurement sites. A second measure involved the timing of a late feature of the LDV pulse contour, which was interpreted as reflection wave latency and thus a measure of round-trip travel time. Both LDV measures agreed with the conventional PTT measure, in disclosing increased PWV during periods of active rebreathing. These results thus provide additional evidence that measures based on the non-contact LDV technique might provide surrogate measures for those obtained using conventional, more obtrusive assessment methods that require attached sensors.

Effect of Aspirin Supplementation on Hemostatic Responses in Firefighters Aged 40 to 60 Years

Sudden cardiovascular events account for approximately 45% to 50% of all duty-related deaths among firefighters and a disproportionate number of these fatalities occur after strenuous fire suppression activities. The purpose of this study was to evaluate the effect of acute and chronic aspirin supplementation on hemostatic function before and after live firefighting activities in older firefighters. A double-blind, crossover design included 4 treatments: a 2-week aspirin/placebo treatment ("chronic") and a single prefirefighting aspirin/placebo treatment ("acute"). Hemostatic function was assessed in 24 male firefighters (mean age = 48.2 ± 5.9 years) immediately before and after 18 minutes of live-fire firefighting activity. An acute bout of firefighting activity significantly decreased platelet aggregation time and decreased activated partial thromboplastin time. Compared with placebo, acute aspirin supplementation resulted in a significant increase in epinephrine closure time, which was further augmented by chronic supplementation. Aspirin supplementation had no effect on coagulatory or fibrinolytic factors. Our findings suggest that an acute bout of firefighting leads to increased coagulatory potential in older firefighters. In conclusion, aspirin supplementation had an antiplatelet effect that decreased platelet aggregability at rest and after an acute bout of firefighting compared with placebo.

Line of duty firefighter fatalities: an evolving trend over time

Between 1990 and 2012, 2775 firefighters were killed in the line of duty. Myocardial infarction (MI) was responsible for approximately 40% of these mortalities, followed by mechanical trauma, asphyxiation, and burns. Protective gear, safety awareness, medical care, and the age of the workforce have evolved since 1990, possibly affecting the nature of mortality during this 22-year time period. The purpose of this study is to determine whether the causes of firefighter mortality have changed over time to allow a targeted focus in prevention efforts. The U.S. Fire Administration fatality database was queried for all-cause on-duty mortality between 1990 to 2000 and 2002 to 2012. The year 2001 was excluded due to inability to eliminate the 347 deaths that occurred on September 11. Data collected included age range at the time of fatality (exact age not included in report), type of duty (on-scene fire, responding, training, and returning), incident type (structure fire, motor vehicle crash, etc), and nature of fatality (MI, trauma, asphyxiation, cerebrovascular accident [CVA], and burns). Data were compared between the two time periods with a χ test. Between 1990 and 2000, 1140 firefighters sustained a fatal injury while on duty, and 1174 were killed during 2002 to 2012. MI has increased from 43% to 46.5% of deaths (P = .012) between the 2 decades. CVA has increased from 1.6% to 3.7% of deaths (P = .002). Asphyxiation has decreased from 12.1% to 7.9% (P = .003) and burns have decreased from 7.7% to 3.9% (P = .0004). Electrocution is down from 1.8% to 0.5% (P = .004). Death from trauma was unchanged (27.8 to 29.6%, P = .12). The percentage of fatalities of firefighters over age 40 years has increased from 52% to 65% (P = .0001). Fatality by sex was constant at 3% female. Fatalities during training have increased from 7.3% to 11.2% of deaths (P = .00001). The nature of firefighter mortality has evolved over time. In the current decade, line-of-duty mortality is more likely to occur during training. Mortality from burns, asphyxiation, and electrocution has decreased; but death from MI and CVA has increased, particularly in older firefighters. Outreach and education should be targeted toward vehicle safety, welfare during training, and cardiovascular disease prevention in the firefighter population.

The impact of sleep restriction while performing simulated physical firefighting work on cortisol and heart rate responses

PURPOSE

Physical work and sleep restriction are two stressors faced by firefighters, yet the combined impact these demands have on firefighters' acute stress responses is poorly understood. The purpose of the present study was to assess the effect firefighting work and sleep restriction have on firefighters' acute cortisol and heart rate (HR) responses during a simulated 3-day and 2-night fire-ground deployment.

METHODS

Firefighters completed multiple days of simulated physical work separated by either an 8-h (control condition; n = 18) or 4-h sleep opportunity (sleep restriction condition; n = 17). Salivary cortisol was sampled every 2 h, and HR was measured continuously each day.

RESULTS

On day 2 and day 3 of the deployment, the sleep restriction condition exhibited a significantly higher daily area under the curve cortisol level and an elevated cortisol profile in the afternoon and evening when compared with the control condition. Firefighters' HR decreased across the simulation, but there were no significant differences found between conditions.

CONCLUSION

Findings highlight the protective role an 8-h sleep opportunity between shifts of firefighting work has on preserving normal cortisol levels when compared to a 4-h sleep opportunity which resulted in elevated afternoon and evening cortisol. Given the adverse health outcomes associated with chronically high cortisol, especially later in the day, future research should examine how prolonged exposure to firefighting work (including restricted sleep) affects firefighters' cortisol levels long term. Furthermore, monitoring cortisol levels post-deployment will determine the minimum recovery time firefighters need to safely return to the fire-ground.

Effect of aspirin on acute changes in peripheral arterial stiffness and endothelial function following exertional heat stress in firefighters: The factorial group results of the Enhanced Firefighter Rehab Trial

Peripheral arterial stiffness and endothelial function, which are independent predictors of cardiac events, are abnormal in firefighters. We examined the effects of aspirin on peripheral arterial stiffness and endothelial function in firefighters. Fifty-two firefighters were randomized to receive daily 81 mg aspirin or placebo for 14 days before treadmill exercise in thermal protection clothing, and a single dose of 325 mg aspirin or placebo immediately following exertion. Peripheral arterial augmentation index adjusted for a heart rate of 75 (AI75) and reactive hyperemia index (RHI) were determined immediately before, and 30, 60, and 90 minutes after exertion. Low-dose aspirin was associated with lower AI75 (-15.25±9.25 vs -8.08±10.70, p=0.014) but not RHI. On repeated measures analysis, treatment with low-dose aspirin before, but not single-dose aspirin after exertion, was associated with lower AI75 following exertional heat stress (p=0.018). Low-dose aspirin improved peripheral arterial stiffness and wave reflection but not endothelial function in firefighters.

Vascular and central hemodynamic changes following exercise-induced heat stress

This study examined the effects of moderate exercise-induced heat stress (EIHS) on vascular function, central hemodynamic load and indices of coronary perfusion. Vascular-hemodynamic measures were collected in 12 healthy men (aged 22±3 years) pre and post 100 minutes of moderate, intermittent exercise in two randomized conditions: heat stress (HS; wearing firefighter personal protective equipment (PPE)), and no heat stress (NHS; wearing a cooling shirt and equivalent PPE weight). Aortic blood pressure, reflected wave pressure (Pb), systolic (SPTI) and diastolic pressure time-integral (DPTI), and aortic stiffness were assessed before and after each condition. SPTI was significantly greater, and DPTI and Pb were significantly lower for HS-post compared to NHS-post (p<0.05). Pulse wave velocity was not different between conditions. In conclusion, EIHS does not affect aortic stiffness, but increases indices of myocardial work and reduces indices of coronary perfusion which may be related to chronotropic responses to EIHS. The mismatch between oxygen demand and oxygen supply may increase cardiac vulnerability to ischemia during strenuous work in the heat.

Cardiac strain associated with high-rise firefighting

Although numerous studies have reported the physiological strain associated with firefighting, cardiac responses during a large-scale fire operation have not been reported and cardiac responses have not been compared based on crew assignment. The aims of this study were (1) to characterize cardiac strain during simulated high-rise firefighting, and (2) to compare the cardiac strain associated with different work assignments (fire suppression vs. search and rescue) and different modes of vertical ascent (stairs vs. elevator). Firefighters (N = 42) completed one assignment (fire suppression, search and rescue, or material support) during one of two trials that differed by ascent mode. Assignments were divided into three phases: Ascent (ascend lobby to 8th floor), Staging (remain in holding area on 8th floor), and Work (perform primary responsibilities). When comparing assignments within the same ascent mode, mean heart rate (HRmean) was higher (p = 0.031) for fire suppression than for search and rescue during Work in the stair trial (170 ± 14 vs. 155 ± 11 beats/min). Search and rescue crews experienced greater cumulative cardiac strain (HRmean × duration) during Work than did fire suppression crews (stairs: 1978 ± 366 vs. 1502 ± 190 beats; elevator: 1755 ± 514 vs. 856 ± 232 beats; p<0.05). When comparing ascent mode, HRmean and peak heart rate (HRpeak) were higher (35-57 beats/min; p≤0.001) for both fire suppression and search and rescue during Ascent and Staging phases in the stairs vs. the elevator trial. During Work, HRmean was higher (p = 0.046) for search and rescue in the stairs vs. the elevator trial (155 ± 11 vs. 138 ± 19 beats/min). HRmean and HRpeak were 47 and 34 beats/min higher (p < 0.01), respectively, when materials were transported to the staging area using the stairs compared with the elevator. Study findings suggest that high-rise firefighting results in considerable cardiac strain and that search and rescue and material support crews experienced more cardiac strain than fire suppression crews due primarily to differences in assignment duration. Furthermore, using stairs to transport firefighters and equipment to upper floors results in significantly greater cardiac strain than using the elevator.

Physical and psychological determinants of injury in Ontario forest firefighters

BACKGROUND

Forest firefighters are faced with multiple physical and psychological challenges as a result of their duties. Little is known about the determinants of injury among these workers. The Ontario Ministry of Natural Resources (OMNR) Aviation, Forest Fire and Emergency Services (AFFES) records detailed information on two mutually exclusive types of workplace injury: First aid (self-reported) and Workplace Safety Insurance Board (WSIB, i.e. received medical attention).

AIMS

To identify the contributions of physical and psychological factors on the likelihood of injury among forest firefighters.

METHODS

Participants were male and female forest firefighters aged between 18 and 65. Data were collected using two self-administered instruments: The NEO Personality Inventory and the Job Stress Survey. Secondary data were collected from the OMNR AFFES and data were analysed by way of multivariate statistical procedures.

RESULTS

There were 252 participants. Those who were older, had a history of injury, had high scores for the personality construct of Neuroticism or low scores for the Openness construct were significantly more likely to incur a first aid injury, while those with high experience levels were significantly less likely to incur injury (P < 0.05). High job stress was the only significant predictor of WSIB injury (P < 0.05).

CONCLUSIONS

First aid and WSIB injuries in the OMNR AFFES were quite distinct phenomena and different factors need consideration in their prediction. It is recommended that managers and decision-makers in this field consider factors such as job stress, personality and the prior occurrence of injuries in their assessment of risk.

Inflammatory responses of older firefighters to intermittent exercise in the heat

PURPOSE

Repeated strenuous work in the heat may predispose firefighters to augmented immune responses and inflammation. This study examined the immune responses in 12 older Firefighters (FF) and 12 older Non-Firefighters (Non-FF), and a group of 6 young FF and 6 young Non-FF, following intermittent exercise in the heat.

METHODS

The participants, matched for age, body surface area, body composition, and VO(2peak), cycled 4 × 15 min at moderate-to-high heat production (400 W), each followed by 15-min rest, in dry [10-20% relative humidity (RH)] and humid (60% RH) heat (35 °C). Rectal temperature (T(re)) and heart rate (HR) were measured continuously, and blood samples at baseline (PRE) and following 60-min recovery (POST) were analyzed for Interleukin (IL)-6, Tumor Necrosis Factor (TNF-α), C-reactive protein (CRP), platelet count (PLT), and mean platelet volume (MPV).

RESULTS

No differences were observed for T(re), HR, TNF-α, CRP, or PLT between the FF and Non-FF in either condition. The Non-FF had greater changes in IL-6 (Warm/Dry = +1.10 ± 0.18, Warm/Humid = +2.94 ± 0.74 pg mL(-1)), compared to the FF (Warm/Dry = +0.67 ± 0.17, Warm/Humid = +0.70 ± 0.33 pg mL(-1)), and MPV at PRE/POST compared to the FF. Between the young and older FF and Non-FF, no differences in T(re), HR, PLT, or MPV were observed, however, elevated CRP (Warm/Dry) in the older FF, and IL-6 (Warm/Dry) and TNF-α (both conditions) in the older Non-FF, were observed.

CONCLUSIONS

The elevated IL-6 in the Non-FF is potentially indicative of increased strain in the Non-FF and/or adaptive changes in the FF due to the occupational demands.

Cardiovascular reactivity, stress, and physical activity

Psychological stress has been proposed as a major contributor to the progression of cardiovascular disease (CVD). Acute mental stress can activate the sympathetic-adrenal-medullary (SAM) axis, eliciting the release of catecholamines (NE and EPI) resulting in the elevation of heart rate (HR) and blood pressure (BP). Combined stress (psychological and physical) can exacerbate these cardiovascular responses, which may partially contribute to the elevated risk of CVD and increased proportionate mortality risks experienced by some occupations (e.g., firefighting and law enforcement). Studies have supported the benefits of physical activity on physiological and psychological health, including the cardiovascular response to acute stress. Aerobically trained individuals exhibit lower sympathetic nervous system (e.g., HR) reactivity and enhanced cardiovascular efficiency (e.g., lower vascular reactivity and decreased recovery time) in response to physical and/or psychological stress. In addition, resistance training has been demonstrated to attenuate cardiovascular responses and improve mental health. This review will examine stress-induced cardiovascular reactivity and plausible explanations for how exercise training and physical fitness (aerobic and resistance exercise) can attenuate cardiovascular responses to stress. This enhanced functionality may facilitate a reduction in the incidence of stroke and myocardial infarction. Finally, this review will also address the interaction of obesity and physical activity on cardiovascular reactivity and CVD.

The effectiveness of health interventions in cardiovascular risk reduction among emergency service personnel

PURPOSE

The physical demands and hazards associated with emergency service work place particular stress on responders' cardiovascular systems. Indeed, cardiovascular disease (CVD) is a significant problem for emergency service personnel. Although it may be difficult to alter the cardiovascular health hazards associated with the work environment, it is possible for personnel to control their modifiable CVD risk factors, cardiovascular fitness levels and subsequently, reduce their CVD risk. This review aimed to determine the effectiveness and methodological quality of health interventions designed to mitigate CVD risk in emergency service personnel.

METHODS

A literature search of electronic journal databases was performed. Sixteen relevant studies were assessed for methodological quality using a standardised assessment tool. Data regarding the effectiveness of each intervention were extracted and synthesised in a narrative format.

RESULTS

Fifteen studies were rated 'Weak' and one study was rated 'Strong'. Interventions which combined behavioural counselling, exercise and nutrition were more effective in improving cardiovascular health than nutrition, exercise or CVD risk factor assessment-based interventions alone. Further, CVD risk factor assessment in isolation proved to be an ineffective intervention type to reduce CVD risk.

CONCLUSION

Combined interventions appear most effective in improving the cardiovascular health of emergency service personnel. Accordingly, fire and emergency service agencies should consider trialling multifaceted interventions to improve the cardiovascular health of personnel and avoid interventions focused only on one of nutrition, exercise or CVD risk factor assessment. However, as most studies were methodologically weak, further studies of a higher methodological quality are needed.

Extreme sacrifice: sudden cardiac death in the US Fire Service

Firefighting is a hazardous profession which has claimed on average the lives of 105 US firefighters per year for the past decade. The leading cause of line-of-duty mortality is sudden cardiac death, which accounts for approximately 45% of all firefighter duty-related fatalities. Strenuous physical activity, emotional stress, and environmental pollutants all strain the cardiovascular system, and each can increase the risk of sudden cardiac events in susceptible individuals. Sudden cardiac death is more likely to occur during or shortly after emergency duties such as fire suppression, despite the fact that these duties comprise a relatively small proportion of firefighters' annual duties. Additionally, cardiac events are more likely to occur in firefighters who possess an excess of traditional risk factors for cardiovascular disease along with underlying atherosclerosis and/or structural heart disease. In this review, we propose a theoretical model for the interaction between underlying cardiovascular disease in firefighters and the multifactorial physiological strain of firefighting.

Lifestyle factors predicting changes in aerobic capacity of aging firefighters at 3- and 13-year follow-ups

OBJECTIVE

To describe changes in aging firefighters' aerobic capacity at 3- and 13-year follow-ups, and to investigate the lifestyle factors predicting them. We evaluated the sufficiency of aerobic capacity for the demands of rescue diving.

METHODS

We studied 78 male Finnish firefighters aged 30 to 44 years at baseline. The outcome variable was aerobic capacity (L·min(-1) and mL·kg(-1)·min(-1)). The predictors were exercise, smoking, and drinking habits.

RESULTS

The average annual change (range) in absolute and relative aerobic capacity was -1.12% (-3.43 to 1.39) and -1.33% (-3.98 to 1.63). Exercising at least 4 to 5 times a week was the best protective factor, and regular smoking and more than 15 units of alcohol a week were risk factors for decline in aerobic capacity.

CONCLUSIONS

To prevent the excessive decline of aerobic capacity related to work demands, we must pay particular attention to exercise regularity.