Firefighters’ basal cardiac autonomic function and its associations with cardiorespiratory fitness

A 7-Month Multidisciplinary Healthy Lifestyle Intervention Effectively Improved Cardiometabolic Risk Profile of Firefighters

OBJECTIVE

We investigated the effect of a 7-month healthy lifestyle intervention on cardiometabolic risk factors (CMRF) among male career military firefighters (FFs).

METHODS

Forty-nine FFs participated in a 7-month workplace multiddisciplinary healthy lifestyle intervention designed to reduce CMRF through exercise, diet, and improved sleep. Medical assessments, accelerometry, and surveys at the beginning and end determined program effectiveness.

RESULTS

At the end of the intervention period, there was a significant improvement in measures of body composition and blood glucose. The prevalence of hypertension also decreased significantly ( P < 0.01). The 57% of participants who fully adhered to the program had significantly greater improvements across multiple CMRF. Participants increased their physical activity and improved their diet following the intervention.

CONCLUSIONS

This healthy lifestyle intervention was effective in changing behavior and lowering cardiometabolic risk among FFs.

Evaluation of the relationship between occupational-specific task performance and measures of physical fitness, cardiovascular and musculoskeletal health in firefighters

INTRODUCTION

Firefighters are required to perform physically strenuous tasks such as hose drags, victim rescues, forcible entries and stair climbs to complete their public safety mission. Occupational-specific tasks are often used to evaluate the ability of firefighters to adequately/safely perform their duties. Depending on the regions, occupational-specific tasks include six to eight individual tasks, which emphasize distinct aspects of their physical fitness, while also requiring different levels of cardiovascular (CVH) and musculoskeletal health (MSH). Therefore, the aim of this study was to evaluate the relationship between specific occupational task performance and measures of physical fitness, cardiovascular and musculoskeletal health.

METHODS

Using a cross-sectional design, 282 full-time male and female firefighters were recruited. A researcher-generated questionnaire and physical measures were used to collect data on sociodemographic characteristics, CVH, MSH and weekly physical activity habits. Physical measures were used to collect data on physical fitness and occupational-specific task performance.

RESULTS

Absolute cardiorespiratory fitness (abV̇O2max), grip strength, leg strength, push-ups, sit-ups and lean body mass (all p < 0.001) had an inverse association with completion times on all occupational-specific tasks. Age was positively related to the performance of all tasks (all p < 0.05). Higher heart rate variability (HRV) was associated with better performance on all tasks (all p < 0.05). Bodyfat percentage (BF%) and diastolic blood pressure were positively associated with the step-up task (p < 0.05). Lower back musculoskeletal injury (LoBMSI), musculoskeletal discomfort (MSD), and lower limb MSD were associated with a decreased odds of passing the step-up. Upper body MSIs (UBMSI), LoBMSIs and Lower back MSD were associated with decreased odds of passing the rescue drag.

CONCLUSION

Firefighters that were taller, leaner, stronger and fitter with a more favourable CVH profile, higher HRV and less musculoskeletal discomfort performed best on all occupational-specific tasks.

Physical fitness, cardiovascular and musculoskeletal health, and occupational performance in firefighters

Introduction

To perform their work efficiently and safely, firefighters should maintain all aspects of physical fitness. Cardiac-related incidents are the leading cause of duty-related deaths in firefighters, and many firefighters have poor musculoskeletal health (MSH) that hinder their occupational performance (OP). Establishing the relationship between physical fitness, cardiovascular health (CVH), MSH and OP may add new insight on the most significant factors influencing OP in firefighters, specifically in the City of Cape Town Fire and Rescue Service (CoCTFS), which had not been studied before. Therefore, the purpose of this study was to investigate whether physical fitness, CVH and MSH were associated with OP in firefighters, in the COCTFRS.

Methods

This cross-sectional study included 283 full-time firefighters aged 20-65 years from Cape Town, South Africa. A researcher-generated questionnaire was used to collect data on sociodemographic characteristics, lifestyle factors and MSH. Physical measures were used to collect information on physical fitness, CVH, and OP [using a physical ability test (PAT)]. Linear and binary logistic regressions, adjusted for age, sex, height and weekly metabolic equivalent minutes (WMETM), multivariate analysis of covariance (MANCOVA), adjusted for age, sex, height and body mass index (BMI) and backward stepwise regressions were used to investigate the associations between the various constructs.

Results

From multivariable analyses, age, lean body mass, body fat percentage (BF%), estimated absolute oxygen consumption (abV̇O2max), grip strength, leg strength, push-ups, sit-ups, WMETM and heart rate variability were associated with PAT completion times (all p < 0.01). The MANCOVA showed a significant difference between performance categories of the PAT based on physical fitness and CVH (both p < 0.001). WMETM, BF%, abV̇O2max, grip strength, leg strength and sit-ups explained the highest proportion (50.5%) of the variation in PAT completion times.

Conclusion

Younger, non-obese, fitter and stronger firefighters, with a better CVH status, performed significantly better and were most likely to pass the PAT in firefighters, in Cape Town, South Africa. Firefighters should maintain high levels of physical fitness and a good level of CVH to ensure a satisfactory level of OP.

Association between Physical Fitness and Cardiovascular Health in Firefighters

Firefighters perform strenuous work in dangerous and unpredictable environments requiring optimal physical conditioning. The aim of this study was to investigate the association between physical fitness and cardiovascular health (CVH) in firefighters. This cross-sectional study systematically recruited 309 full-time male and female firefighters between the ages of 20 to 65 years in Cape Town, South Africa. Physical fitness was assessed using absolute (abV̇O2max) and relative oxygen consumption (relVO2max), grip and leg strength, push-ups and sit-ups, sit-and-reach for flexibility and lean body mass (LBM). CVH encompassed age, smoking, blood pressure (BP), blood glucose, lipid profile, body mass index, body fat percentage (BF%), and waist circumference. Linear regressions and logistic regressions were applied. Multivariable analysis indicated that relVO2max was associated with systolic BP (p < 0.001), diastolic BP (p < 0.001), non-fasting blood glucose (p < 0.001), and total cholesterol (p = 0.037). Poor CVH index was negatively associated with relV̇O2max (p < 0.001), leg strength (p = 0.019), and push-ups (p = 0.012). Furthermore, age was inversely associated with V̇O2max (p < 0.001), push-up and sit-up capacity (p < 0.001), and sit-and-reach (p < 0.001). BF% was negatively associated with abV̇O2max (p < 0.001), grip and leg strength (p < 0.001), push-ups (p = 0.008), sit-ups (p < 0.001), and LBM (p < 0.001). Cardiorespiratory fitness, muscular strength, and muscular endurance were significantly associated with a better overall CVH profile.

The effect of cranial techniques on the heart rate variability response to psychological stress test in firefighter cadets

Heart rate variability (HRV) is a simple tool to monitor cardiovascular stress. The proper function of the cardiovascular system is a problem among firefighters. Physical activity has health benefits correlated with psychological stress. Physically active people should be more resilient to psychological stress, but this has not always been demonstrated. The aim of this study was to determine whether cranial techniques would have an effect on HRV parameters. Osteopathy in the cranium reduces stress and improves cardiovascular function. Fifty-seven firefighter cadets aged 18-24 years (21.63 ± 1.41) participated in the study. All subjects had their heart rate variability measured and were randomly assigned either to the cranial techniques (CS) group, with therapy performed once a week for 5 weeks), or to the control group (CO). After 5 weeks, heart rate variability was measured again in both groups. In the Friedman test, in the CS group there was a statistically significant effect of cranial techniques on Heart Rate (HR) and Low Frequency (LF), but not on High Frequency (HF); in the CO group, a statistically significant difference was observed for HR, HF and LF. In the Nemenyi test, in the CS group there was a statistically significant difference for HR and LF and in the CO group for HR, HF and LF. After applying hierarchical clustering with Euclidean measure and the complete method, dendrograms were drawn up showing similarities for HR, HF and LF values. The cranial techniques and touch might exert a beneficial effect on HRV. Both factors can be used in stressful situations to lower HRV.

Association between Cardiovascular Disease Risk Factors and Cardiorespiratory Fitness in Firefighters: A Systematic Review and Meta-Analysis

Approximately 45% of on-duty related mortalities were due to sudden cardiac death, with many of these fatalities related to cardiovascular disease and overexertion, while performing emergency duties. Therefore, the aim of this systematic review was to determine the association between cardiovascular disease risk factors and cardiorespiratory fitness in firefighters. A literature search of PubMed, SCOPUS, Web of Science, Embase, EBSCOHost, and ScienceDirect was conducted; the Rayyan® intelligent systematic review tool was used to screen and select studies for inclusion. The appraisal tool for cross-sectional studies and the Critical Appraisal Skills Programme toolkit were used for methodological assessment of included studies. Data were analyzed using the Review Manager 5.3 and MedCalc® statistical softwares to determine the effects of obesity (Z = 10.29, p < 0.001) and aging (Z = 4.72, p < 0.001) on cardiorespiratory fitness. Furthermore, there was a significant effect for cardiorespiratory fitness level on systolic blood pressure (Z = 5.94, p < 0.001), diastolic blood pressure (Z = 2.45, p < 0.001), total cholesterol levels (Z = 3.80, p < 0.001), low-density lipoprotein cholesterol (Z = 4.44, p < 0.001), triglycerides (Z = 3.76, p < 0.001) and blood glucose concentration (Z = 4.78, p < 0.001). Cardiovascular disease risk factors and cardiorespiratory fitness were significantly and inversely associated in firefighters. Fire service departments should adopt behavioral intervention strategies to maintain optimum cardiovascular disease risk factor profiles and cardiorespiratory fitness among firefighters to ensure their occupational well-being.

A Pilot Study on the Relationship between Cardiovascular Health, Musculoskeletal Health, Physical Fitness and Occupational Performance in Firefighters

Firefighters’ face life threatening situations and are frequently exposed to numerous physical, chemical, biological, ergonomic and psychosocial hazards. The purpose of this pilot study was to investigate the feasibility of conducting a large-scale study on cardiovascular and musculoskeletal health, physical fitness and occupational performance of firefighters. We conducted a cross-sectional pilot study by recruiting 36 firefighters. A researcher-generated questionnaire and physical measures were used to collect data on sociodemographic characteristics, cardiovascular and musculoskeletal health, physical fitness and occupational performance using a physical ability test (PAT). We documented a high equipment and intra-assessor reliability (r > 0.9). The potential logistic and/or administrative obstacles in the context of a larger study were discerned. Data were successfully retrieved using available equipment and survey instruments. Hypertension (30.6%) dyslipidaemia (33.3%), obesity (36.1%) and physical inactivity (66.7%) were the most prevalent cardiovascular disease risk factors. A significant difference between genders in total PAT completion time was also seen (p < 0.001). Cardiorespiratory fitness, lean body mass, grip strength and leg strength were significantly associated with occupational performance (p < 0.001). The pilot study supports the larger study feasibility and verified equipment and assessors’ reliability for research. Cardiovascular health, musculoskeletal health and physical fitness may be related to PAT performance.

Cardiovascular Disease Risk Factors, Musculoskeletal Health, Physical Fitness, and Occupational Performance in Firefighters: A Narrative Review

Introduction

Firefighting is a strenuous occupation that requires firefighters to be in peak physical condition. However, many firefighters have risk factors for cardiovascular disease, impaired musculoskeletal health, and are not physically fit for duty, which all negatively impact their occupational performance. Therefore, the aim of this review is to determine the relationship between cardiovascular disease risk factors, musculoskeletal health, physical fitness, and occupational performance in firefighters.

Methods

The electronic databases PubMed, SCOPUS, and Web of Science were searched online via the library portal of the University of the Western Cape. Publications and grey literature between the years 2000 to present were used. In total, 2607 articles were identified; after the removal of duplicates 1188 articles were then screened, and were excluded for not meeting initial screening criteria. The remaining 209 full-text articles were screened based on the inclusion and exclusion criteria, where 163 articles were excluded. Only studies that were quantitative were included. This left 46 articles that were then finally included in the current narrative review.

Results

The current literature indicated that significant relationships existed between cardiovascular risk factors, musculoskeletal health, physical fitness, and occupational performance. The results indicated firefighters who were aged, obese, physically inactive, cigarette smokers, and unfit were at the highest risk for cardiovascular and musculoskeletal health complications, and unsatisfactory occupational performance. Musculoskeletal health complications significantly affected occupational performance and work ability and were related to physical fitness of firefighters. Most cardiovascular risk factors were related to physical fitness, and all physical fitness parameters were related to occupational performance in firefighters.

Conclusion

The overwhelming evidence in the current review established that physical fitness is related to occupational performance. However, the relationship between cardiovascular risk factors and musculoskeletal health in relation to occupational performance is less clear and still understudied. Significant gaps remain in the literature.

The effects of a 6-month mandatory military police academy training on recruits’ physical fitness

BACKGROUND: Physical fitness for health and professional performance play important roles in police workforce considering that policing is a dangerous job, associated with high physical demands. OBJECTIVES: (1) To evaluate the effects of a 6-month course of police academy training on health-related physical fitness (HRPF) of military police recruits. (2) To investigate whether recruits’ HRPF still met the academy entry standards after an unsupervised 7-month period prior to academy. METHODS: We conducted an observational and longitudinal study with 219 male police recruits (aged 25.5±3.6 years; BMI of 24.4±2.5 kg/m2). HRPF parameters included the Cooper 12-min running test for cardiorespiratory fitness (CRF), curl-ups, pull-ups and push-ups for muscle strength/endurance which were evaluated 3 times: 7 months prior to academy course and pre- and post- the academy training period. RESULTS: Participants maintained optimal age-related HRPF during the unsupervised period prior to academy. After academy training upon graduation, all HRPF parameters further increased an average of 7.7 to 69.0% (p < 0.001; calculated Cohen’s d effect size ≥0.95). CRF was the only HRPF that improved less than 10% after the academy course. CONCLUSIONS: Police recruits that had passed the application fitness standards maintained their HRPF prior to academy, and all their HRPF parameters increased after a 6-month academy training period which was not primarily focused on exercise training. Among all components of HRPF, CRF appears to be the most challenging one to improve among police recruits. Our findings suggest that regular training with minimum physical standards could be potentially beneficial to police officers’ health and career longevity.

Relationship Between Physical Activity, Coronary Artery Disease Risk Factors and Musculoskeletal Injuries in the City of Cape Town Fire and Rescue Service

Musculoskeletal injuries in firefighters are a common occurrence, that increase as firefighters age, and may be related to the firefighters’ physical activity habits outside of the job. Certain CAD risk factors, such as obesity, cigarette smoking and ageing may be linked to increased injury risk in firefighters. Although firefighters may meet the recommended minimum physical activity minutes, they may remain at risk for sustaining musculoskeletal injuries. Therefore, this study aims to determine the relationship between physical activity and CAD risk factors, between CAD risk factors and musculoskeletal injuries and between physical activity and musculoskeletal injuries. A total of 124 full-time firefighters, males and females, were conveniently recruited from the City of Cape Town Fire and Rescue Service. A researcher-generated questionnaire was used to collect injury, CAD risk factor and physical activity data. The proportion of firefighters who participated in leisure-time physical activity (LTPA) was 63.7%, and those who were physically inactive was 69.4%. The prevalence musculoskeletal injuries among all firefighters was 27.4%. The most prevalent musculoskeletal injury was shoulder injuries in 35.3% of firefighters, followed by multiple injuries in 26.5% and back injuries in 14.7%. Age was a significant predictor of physical inactivity in firefighters [P = .002, OR = 1.08], BMI was a significant predictor of physical inactivity [P = .050, OR = 1.08], cigarette smoking was a significant predictor of firefighters not exercising [P = .007, OR = 2.31] and the total amount of vigorous-intensity exercise was a significant predictor of musculoskeletal injuries [P = .050, OR = 1.00]. In conclusion, older firefighters were more physically inactive and had a higher prevalence of musculoskeletal injuries, and the latter decreased significantly after the age of 50 years. Emphasis should be placed on firefighters exercising in their leisure-time, especially as they aged.

Monitoring stress and allostatic load in first responders and tactical operators using heart rate variability: a systematic review

BACKGROUND

Awareness of the cumulative stress placed on first responders and tactical operators is required to manage acute fatigue, which can impair occupational performance, and may precipitate negative chronic health outcomes. The aim of this review was to investigate the utility of heart rate variability (HRV) to monitor stress and allostatic load among these populations.

METHODS

A systematic search of Academic Search Complete, MEDLINE complete, PsycINFO, SPORTDiscus and Scopus databases was conducted. Eligibility criteria: original peer reviewed research articles, written in English, published between 1985 and 2020, using human participants employed as a first responder or tactical operator, free from any psychological disorder.

RESULTS

Of the 360 articles screened, 60 met the inclusion criteria and were included for full text assessment. Articles were classified based on single or repeated stressor exposure and the time of HRV assessment (baseline, during stressor, post stressor). Singular stressful events elicited a reduction in HRV from baseline to during the event. Stressors of greater magnitude reduced HRV for extended durations post stressor. Lower resting HRV was associated with lower situational awareness and impaired decision-making performance in marksmanship and navigation tasks. There were insufficient studies to evaluate the utility of HRV to assess allostatic load in repeated stressor contexts.

CONCLUSION

A reduction in HRV occurred in response to acute physical and cognitive occupational stressors. A slower rate of recovery of HRV after the completion of acute occupational stressors appears to occur in response to stressors of greater magnitude. The association between lower HRV and lower decision-making performance poses as a useful tool but further investigations on within subject changes between these factors and their relationship is required. More research is required to investigate the suitability of HRV as a measure of allostatic load in repeated stress exposures for fatigue management in first responder and tactical operators.

Cardiovascular risk and quality of life in supermarket cashiers: The role of physical activity

BACKGROUND

Occupations might influence the employees' psychophysical conditions and an important issue is the human activity mechanization, which favors a hypokinetic work status and leads to several chronic diseases. One of the most hypokinetic occupations is the supermarket cashier, in which the individual may spend many hours a day in the same body position.

OBJECTIVE

The goal of this study was to evaluate the association between cardiovascular risk, quality of life and physical activity level in supermarket cashiers.

METHODS

This is a cross-sectional study which included 200 supermarket cashiers aged 20 to 41 years from São Paulo, Brazil. The following cardiovascular risk factors were evaluated: overweight, obesity, hypertension, diabetes mellitus, and tobacco smoking. Physical activity level and quality of life were assessed with the short-form of the International Physical Activity Questionnaire (IPAq) and World Health Organization Quality of Life (WHOQOL), respectively. Student t test and Chi-square were carried out to evaluate mean gender comparations and frequency, respectively. Logistic regression models were applied to determine the association between cardiovascular risk factors and physical activity level.

RESULTS

The prevalence for all cardiovascular risk factors was significantly high in the cashiers with a low physical activity level. However, there was a significant reduction in several risk factors in the groups with moderate and high physical activity levels. The odds ratio values were significantly reduced for the association between the cardiovascular risk factors and the moderate and high physical activity levels. The cashiers with moderate and high physical activity levels showed significantly higher quality of life scores for the social and environmental domain.

CONCLUSIONS

A high physical activity level is positively related to quality of life in supermarket cashiers.

Higher cardiorespiratory fitness is strongly associated with lower cardiovascular risk factors in firefighters: a cross-sectional study in a German fire brigade

Previous studies have shown significant cardiovascular risks in firefighters and that they suffer from cardiovascular events, especially on duty. Otherwise, adequate cardiorespiratory fitness is considered to have a protective effect in reducing cardiovascular complications. Therefore, the study aimed to evaluate the association between cardiorespiratory fitness and cardiovascular risks factors in firefighters. We enrolled ninety-seven male German firefighters in this cross-sectional study of cardiorespiratory fitness and cardiovascular risk factors. We used spiroergometry testing to estimate oxygen consumption to determine cardiorespiratory fitness and to calculate metabolic equivalents. We evaluated cardiovascular risk factors included nicotine consumption, lipid profiles, body composition, resting blood pressure, and heart rate. We evaluated cardiovascular risk factors included nicotine consumption, lipid profiles, body composition, resting blood pressure and heart rate. The comparison of association between cardiorespiratory fitness and cardiovascular risk factors was performed by using χ²-test, analysis of variance, general linear regression with/without adjustment for age and body mass index (BMI). This study demonstrated a strong association between lower cardiovascular risk factors and higher cardiorespiratory fitness. There were significantly lower values for BMI, waist circumference, body fat percentage and resting systolic blood pressure, triglycerides, and total cholesterol (all p < 0.0443, age-adjusted) with increased cardiorespiratory fitness. Only 19.6% (n = 19) of the examined firefighters were classified as “fit and not obese”, 48.4% (n = 47) were “low fit and not obese” and 30.9% (n = 30) were “low fit and obese”. The results clarify that increasing cardiorespiratory fitness is a fundamental point for the reduction and prevention of cardiovascular complications in firefighters. It could be demonstrated, especially for central risk factors, particularly BMI, waist circumference, sytolic resting blood pressure and triglyceride values. Therefore, firefighters should be motivated to increase their cardiorespiratory fitness for the beneficial effect of decreasing cardiovascular risk profile.

Relationships Between Heart Rate Variability, Occupational Performance, and Fitness for Tactical Personnel: A Systematic Review

Objectives: Heart Rate Variability has gained substantial interest in both clinical and athletic settings as a measurement tool for quantifying autonomic nervous system activity and psychophysiological stress. However, its uses in tactical work settings, such as military, police, and firefighting environments, remain controversial. Given the physical, mental, and emotional stress public safety personnel face both operationally and in training, heart rate variability measurement may be key in promoting their health, safety and operational effectiveness.

Methods: This study identified, critically appraised, and summarized primary studies investigating relationships between heart rate variability and outcomes of interest to tactical personnel. Key literature databases were searched, and quality assessment checklists were applied to analyze retained literature. The results of the screening and assessment processes, along with key data extracted from each study were summarized and tabulated. Research gaps were also identified to facilitate improvements to how tactical personnel and health or performance providers may best utilize heart rate variability to monitor or promote personnel health and performance, and thereby facilitate public safety.

Results: Twenty studies were included and were all of generally high quality. Cohort size, length of follow-up, measurement objectives, data acquisition, and data analysis all varied considerably across studies, precluding meta-analysis. However, study results correlating heart rate variability and relevant outcomes indicated that overall, heart rate variability is an effective indicator of key fitness and performance elements in the tactical work setting.

Conclusions: Heart rate variability can be an effective health and performance tool in tactical work environments. However, measurement methods must be carefully selected and applied. Further research is required to understand causal relationships. Specifically, larger cohort inclusion and the isolation and study of specific variables unique to public safety work and training may improve the effectiveness of heart rate variability measurement to provide meaningful information to end users and providers.

Cardiorespiratory fitness assessment among firefighters: Is the non-exercise estimate accurate?

BACKGROUND

Minimum cardiorespiratory fitness (CRF) has been recommended for firefighters due to job requirements. Thus, it is important to identify accurate and readily available methods to assess CRF in this population. Non-exercise CRF estimates (NEx-CRF) have been proposed but this approach requires validation in this population.

OBJECTIVE

To evaluate the accuracy of a NEx-CRF, as compared to a field maximum exercise test, among career military firefighters of both genders using a comprehensive agreement analysis.

METHODS

We evaluated the accuracy of a NEx-CRF estimate compared to the Cooper 12 min running test among 702 males and 106 female firefighters.

RESULTS

Cooper and NEx-CRF tests yielded similar CRF in both genders (differences <1.8±4.7 ml/kg-1.min-1; effect size <0.34). However, NEx-CRF underestimated Cooper-derived CRF among the fittest firefighters. NEx-CRF showed moderate to high sensitivity/specificity to detect fit or unfit firefighters (71.9% among men and 100% among women). Among men, the NEx-CRF method correctly identified most firefighters with less than 11 METs or greater than 13 METs, but showed lower precision to discriminate those with CRF between 11-13 METs.

CONCLUSIONS

The NEx-CRF method to estimate firefighters' CRF may be considered as an alternative method when an exercise-based method is not available or may be used to identify those who require more traditional testing (CRF 11-13 METs).

The effects of varying doses of caffeine on cardiac parasympathetic reactivation following an acute bout of anaerobic exercise in recreational athletes

BACKGROUND

To examine the effects of varying doses of caffeine on autonomic reactivation following anaerobic exercise.

METHODS

Recreationally active males (N = 20; 24 ± 2y) participated in a randomized, double-blind, placebo-controlled, crossover study where participants ingested: [1] Control (CON; no supplement), [2] a non-caffeinated placebo (PLA), [3] 3-mg∙kg- 1 of caffeine (CAF3) or [4] 6-mg∙kg- 1 of caffeine (CAF6) prior to Wingate testing. Parasympathetic (lnRMSSD, primary outcome) and global HRV (lnSDNN, secondary outcome) were assessed at rest (i.e., pre-ingestion), 45-min post-ingestion, and 5-min and 35-min post-exercise recovery. We used a GLM to assess mean (95% CI) changes from pre-ingestion baseline.

RESULTS

Overall, we observed a significant trend for lnRMSSD and lnSDNN (both, p = 0.001, ηp2 = 0.745). Forty-five minutes after treatment ingestion, we observed a significant increase in lnRMSSD for CAF3 (0.15 ms, 95%CI, 0.07,0.24) and CAF6 (0.16 ms, 95%CI, 0.06,0.25), both being significant (both, p <  0.004) vs. CON (- 0.02 ms, 95%CI, - 0.09,0.04). Five-minutes after exercise, all treatments demonstrated significant declines in lnRMSSD vs. baseline (all, p <  0.001). After 35-min of recovery, lnRMSSD returned to a level not significantly different than baseline for CAF3 (0.03 ms, 95%CI, - 0.05, 0.12) and CAF6 (- 0.03 ms, 95%CI, - 0.17, 0.10), while PLA (- 0.16 ms, 95%CI, - 0.25, - 0.06) and CON (- 0.17 ms, 95%CI, - 0.28, - 0.07) treatments remained significantly depressed. A similar pattern was also observed for SDNN.

CONCLUSION

Caffeine ingestion increases resting cardiac autonomic modulation and accelerates post-exercise autonomic recovery after a bout of anaerobic exercise in recreationally active young men. However, no differences between caffeine doses on cardiac autonomic reactivity were observed.

Nível de atividade física e sobrecarga cardiovascular em bombeiros militares durante combate a incêndio florestal: um estudo exploratório

Resumo Introdução : combates a incêndios florestais expõem bombeiros a elevado risco cardiovascular. Objetivo : avaliar o nível de atividade física (ATF), o comportamento sedentário e a sobrecarga cardiovascular de bombeiros durante um combate a incêndio florestal de grande porte. Métodos : durante 9 dias de atividade, 24h/dia, avaliaram-se 7 bombeiros do sexo masculino. Os participantes tiveram a frequência cardíaca (FC) medida a cada segundo e a ATF registrada por um sensor de movimento, do tipo acelerômetro, a cada 60 segundos. Foram computadas as médias dos registros do 2º, 3º e 4º dias. A ATF e o comportamento sedentário foram avaliados pelo vetor magnitude do acelerômetro, e a sobrecarga cardiovascular, pelo comportamento da FC. Resultados : os participantes apresentaram média de 112 (DP 24) min/dia de ATF moderada/vigorosa (MV), acumularam em média 14.803 (DP 1.667) passos/dia e gasto energético de 1.860 (DP 481) kcal/dia. A sobrecarga cardiovascular permaneceu, em média, 47 (DP 42) min/dia em esforço vigoroso e 8 (DP 12) min/dia em esforço muito vigoroso. Conclusão: os bombeiros avaliados acumularam mais que o dobro da recomendação mínima de ATF-MV semanal em três dias, apresentaram mais de 50 min/dia de elevada sobrecarga cardiovascular e pouco tempo em comportamento sedentário, se comparados a outras profissões.