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The fire service suffers from high rates of cardiovascular disease and poor overall health, and firefighters often suffer fatal and non-fatal injuries while on the job. Most fatal injuries result from sudden cardiac death, while non-fatal injuries are to the musculoskeletal system. Previous works suggest a mechanistic link between several health and performance variables and injury risk. In addition, studies have suggested physical activity and nutrition can improve overall health and occupational performance. This review offers practical applications for exercise via feasible training modalities as well as nutritional recommendations that can positively impact performance on the job. Time-efficient training modalities like high-intensity interval training and feasible modalities such as resistance training offer numerous benefits for firefighters. Also, modifying and supplementing the diet and can be advantageous for health and body composition in the fire service. Firefighters have various schedules, making it difficult for planned exercise and eating while on shift. The practical training and nutritional aspects discussed in this review can be implemented on-shift to improve the overall health and performance in firefighters.
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OBJECTIVE: This study investigated reliability and validity of muscle cross-sectional area and echo intensity using an automatic image analysis program. METHODS: Twenty-two participants completed two data collection trials consisting of ultrasound imaging of the vastus lateralis (VL) at 10 and 12 MHz. Images were analyzed manually and with Deep Anatomical Cross-Sectional Area (DeepACSA). Reliability statistics (i.e., intraclass correlation coefficient [ICC] model 2,1, standard error of measure expressed as a percentage of the mean [SEM%], minimal differences [MD] values needed to be considered real) and validity statistics (i.e., constant error [CE], total error [TE], standard error of the estimate [SEE]) were calculated. RESULTS: Automatic analyses of ACSA and EI demonstrated good reliability (10 MHz: ICC2,1 = 0.83 - 0.90; 12 MHz: ICC2,1 = 0.87-0.88), while manual analyses demonstrated moderate to excellent reliability (10 MHz: ICC2,1 = 0.82-0.99; 12 MHz: ICC2,1 = 0.73-0.99). Automatic analyses of ACSA presented greater error at 10 (CE = -0.76 cm2, TE = 4.94 cm2, SEE = 3.65 cm2) than 12 MHz (CE = 0.17 cm2, TE = 3.44 cm2, SEE = 3.11 cm2). Analyses of EI presented greater error at 10 (CE = 3.35 a.u., TE = 2.70 a.u., SEE = 2.58 a.u.) than at 12 MHz (CE = 3.21 a.u., TE = 2.61 a.u., SEE = 2.34 a.u.). CONCLUSION: The results suggest the DeepACSA program may be less reliable compared to manual analysis for VL ACSA but displayed similar reliability for EI. In addition, the results demonstrated the automatic program had low error for 10 and 12 MHz.
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Ultrassonografia , Humanos , Reprodutibilidade dos Testes , Ultrassonografia/métodos , Masculino , Adulto , Feminino , Adulto Jovem , Tamanho do Órgão , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/anatomia & histologia , Músculo Quadríceps/diagnóstico por imagem , Músculo Quadríceps/anatomia & histologia , Processamento de Imagem Assistida por Computador/métodosRESUMO
Quantifying skeletal muscle size is necessary to identify those at risk for conditions that increase frailty, morbidity, and mortality, as well as decrease quality of life. Although muscle strength, muscle quality, and physical performance have been suggested as important assessments in the screening, prevention, and management of sarcopenic and cachexic individuals, skeletal muscle size is still a critical objective marker. Several techniques exist for estimating skeletal muscle size; however, each technique presents with unique characteristics regarding simplicity/complexity, cost, radiation dose, accessibility, and portability that are important factors for assessors to consider before applying these modalities in practice. This narrative review presents a discussion centred on the theory and applications of current non-invasive techniques for estimating skeletal muscle size in diverse populations. Common instruments for skeletal muscle assessment include imaging techniques such as computed tomography, magnetic resonance imaging, peripheral quantitative computed tomography, dual-energy X-ray absorptiometry, and Brightness-mode ultrasound, and non-imaging techniques like bioelectrical impedance analysis and anthropometry. Skeletal muscle size can be acquired from these methods using whole-body and/or regional assessments, as well as prediction equations. Notable concerns when conducting assessments include the absence of standardised image acquisition/processing protocols and the variation in cut-off thresholds used to define low skeletal muscle size by clinicians and researchers, which could affect the accuracy and prevalence of diagnoses. Given the importance of evaluating skeletal muscle size, it is imperative practitioners are informed of each technique and their respective strengths and weaknesses.
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Músculo Esquelético , Valor Preditivo dos Testes , Humanos , Músculo Esquelético/diagnóstico por imagem , Reprodutibilidade dos Testes , Sarcopenia/diagnóstico por imagem , Sarcopenia/fisiopatologia , Sarcopenia/diagnóstico , Força Muscular , Diagnóstico por Imagem/métodosRESUMO
An air consumption test (ACT) is a physical ability test used in the fire service. The purpose of this study was to compare demographics and physiological differences between slow versus fast performers on an ACT. 160 career firefighters had air consumption, total task time, body mass index (BMI), peak heart rate (HRpeak), body fat percentage (BF%), and oxygen consumption (VO2peak) measured. K-means clustering was used to dichotomize between slow and fast groups during an ACT. Independent samples t-tests and Cohen's d measures of effect size were used to examine differences between groups. There were no significant differences in groups for age (t = -1.05, p = 0.30, d = 0.17), BMI (t = -1.85, p = 0.07, d = 0.32), or HRpeak (t = 0.99, p = 0.32, d = 0.16). There were significant differences between groups for BF% (t = -3.35, p < 0.01, d = 0.57), relative (t = 3.52, p < 0.01, d = 0.58) and absolute VO2peak (t = 4.29, p < 0.01, d = 0.68), air consumption (t = -4.87, p < 0.01, d = 0.81), and total task time (t = -15.04, p < 0.01, d = 2.58).
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Índice de Massa Corporal , Bombeiros , Frequência Cardíaca , Consumo de Oxigênio , Humanos , Masculino , Adulto , Consumo de Oxigênio/fisiologia , Frequência Cardíaca/fisiologia , Feminino , Pessoa de Meia-Idade , Análise e Desempenho de Tarefas , Fatores de Tempo , Teste de EsforçoRESUMO
The purpose of this study was to examine the influence of inter-limb leg lean tissue mass (LTM) asymmetry on stair climb (SC) performance in firefighters. Forty-one career firefighters (age = 32.3 ± 8.2 years, body mass = 92.1 ± 18.6 kg, stature = 178.3 ± 7.9 cm) visited the laboratory on one occasion and completed a whole body and leg composition assessment followed by a timed and weighted SC task. Percent body fat (%BF) and leg LTM were determined during a DEXA scan and regional thigh analysis. Asymmetry was assessed by the percent difference between limbs (dominant limb LTM - non-dominant limb LTM)/dominant limb LTM × 100) and a ± 3% cut-off for asymmetry classification. Participants ascended and descended 26 stairs four times as quickly as possible while wearing a weighted (22 kg) vest. Point biserial correlations were used to assess the relationship of inter-limb leg LTM asymmetry and SC performance before and after controlling for age and %BF. Results indicated that inter-limb leg LTM asymmetry was associated with longer SC task time (poorer performance) both before (r = 0.432, P = 0.005) and after (r = 0.502, P = 0.001) controlling for age and %BF. Our findings indicated that inter-limb leg LTM asymmetry negatively impacts firefighter SC performance, which may be improved with appropriate exercise interventions.
This study examined the influence of leg inter-limb lean tissue mass (LTM) asymmetry on SC performance in career firefighters. We found that inter-limb leg LTM asymmetry was associated with reduced SC performance, prior to and after controlling for age and percent body fat. Interventions that mitigate these asymmetries may improve occupational performance.
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Recent works have shown bioelectrical impedance spectroscopy (BIS) may assess tissue quality. The purpose of this project was to examine associations between ultrasound echo intensity (EI) of quadriceps muscles (vastus lateralis [VL], vastus medialis [VM], vastus intermedius [VI], rectus femoris [RF]) and BIS parameters (R0, R1, C, α, fp), and if the associations are specific to individual muscles or associated with a representation of the entire quadriceps. Twenty-two participants (age: 22 ± 4 years; BMI: 25.47 ± 3.26 kg/m2) participated in all study activities. Participants had transverse ultrasound scans of each individual quadriceps muscle taken at 25, 50, and 75 % of the muscle length to generate an average EI for the VL, VM, VI, and RF, which were further averaged to generate an EI for the entire quadriceps. For BIS, participants were seated with electrodes placed on the thigh to measure the segmental quadriceps. The Cole-impedance model parameters that best fit the BIS data for each participant was used for all analyses. Pearson's correlation coefficient (r) were calculated to determine associations between muscles' EI and BIS parameters. The results suggest averaged EI of individual VL, VM, VI, RF muscles and the average EI of the segmental quadriceps were significantly related to the R0, C, α metrics of the Cole-impedance model representing quadriceps segmental tissues. This supports that segmental BIS may be an appropriate technique for rapid evaluation of segmental muscle quality.
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Músculo Quadríceps , Humanos , Adolescente , Adulto Jovem , Adulto , Impedância Elétrica , Músculo Quadríceps/diagnóstico por imagem , Músculo Quadríceps/fisiologia , UltrassonografiaRESUMO
The fire service command structure encompasses recruit, incumbent firefighter, and officer positions. The purpose of this study was to quantify the effect of rank (recruits, incumbent firefighters, and officers) on health and physical ability characteristics within the fire service. Retrospective data from thirty-seven recruits (age = 29 ± 5 yrs, BMI = 26.5 ± 2.3 kg/m2); eighty-two incumbent firefighters (age = 30 ± 7 yrs, BMI = 28.8 ± 4.3 kg/m2); and forty-one officers (age = 41 ± 6 yrs, BMI = 28.6 ± 4.3 kg/m2) from a single department were used. Participants completed body composition tests (i.e., body fat percentage [%BF] and body mass index [BMI]), an air consumption test (ACT), and cardiopulmonary exercise testing. The ACT consisted of 10 standardized tasks. Five separate one-way analyses of co-variance (ANCOVA) were calculated, accounting for age. Partial eta squared statistics were calculated and Bonferroni-corrected post-hoc analyses were employed. The results demonstrated a significant effect of rank on %BF (F = 9.61, p < 0.001, η2 = 0.10); BMI (F = 3.45, p = 0.02, η2 = 0.05); relative VO2MAX (F = 12.52, p < 0.001; η2 = 0.11); and HRMAX (F = 18.89, p < 0.001, η2 = 0.03), but not on ACT time (F = 0.71, p = 0.55, η2 = 0.01). These outcomes suggest there are variations in anthropometric and physiological metrics of health across firefighter ranks. Administrators should be aware how these markers of health may vary across firefighter ranks.
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INTRODUCTION: The purpose of this study was to examine the impact of age on the affective responses (attitude, feelings, self-efficacy, intention, enjoyment, and fondness) after a worksite circuit-style resistance exercise routine in career firefighters. METHODS: Nineteen young (25.5 ± 3.3 yr) and 19 middle-aged male career firefighters (50.3 ± 3.5 yr) completed 2 d of physical testing at local fire stations. Participants were familiarized with the resistance training exercises (deadlift, shoulder press, lunge, and upright row) at visit 1 and performed a multirepetition maximum (RM) assessment to prescribe the appropriate loads for the resistance exercise bout on visit 2. The resistance training session included three sets of 8 to 10 repetitions per exercise at 80% 1-RM. Participants completed a postexercise questionnaire examining affective responses and a rating of perceived exertion (RPE). Mann-Whitney U tests and an independent t-test were used to determine differences between the young and middle-aged firefighters' affective responses and RPE, respectively. RESULTS: There were no significant differences between groups for any of the six affective responses ( P = 0.062-0.819) or RPE ( P = 0.142). CONCLUSIONS: Age did not influence the perceived effort or affective responses following an acute bout of worksite resistance exercise. Firefighters reported overall positive attitudes, feelings, and fondness paired with high self-efficacy and intention at a training frequency of twice per week. However, confidence, intention, and enjoyment decreased at higher training frequencies (i.e., 3-4x per week). Circuit-style resistance training performed twice per week may be a feasible and practical worksite exercise routine across ages in the fire service.
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Bombeiros , Treinamento Resistido , Pessoa de Meia-Idade , Humanos , Masculino , Esforço Físico/fisiologia , Percepção/fisiologia , Local de TrabalhoRESUMO
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.
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Bombeiros , Transtornos de Estresse por Calor , Infarto do Miocárdio , Exposição Ocupacional , Humanos , Estados Unidos/epidemiologia , Exposição Ocupacional/efeitos adversos , Exposição Ocupacional/análise , Temperatura Alta , Transtornos de Estresse por Calor/epidemiologia , Transtornos de Estresse por Calor/etiologia , Resposta ao Choque TérmicoRESUMO
The purpose of this study was to investigate lower limb blood flow responses under varying blood flow restriction (BFR) pressures based on individualized limb occlusion pressures (LOP) using a commonly used occlusion device. Twenty-nine participants (65.5% female, 23.8 ± 4.7 years) volunteered for this study. An 11.5cm tourniquet was placed around participants' right proximal thigh, followed by an automated LOP measurement (207.1 ± 29.4mmHg). Doppler ultrasound was used to assess posterior tibial artery blood flow at rest, followed by 10% increments of LOP (10-90% LOP) in a randomized order. All data were collected during a single 90-minute laboratory visit. Friedman's and one-way repeated-measures ANOVAs were used to examine potential differences in vessel diameter, volumetric blood flow (VolFlow), and reduction in VolFlow relative to rest (%Rel) between relative pressures. No differences in vessel diameter were observed between rest and all relative pressures (all p < .05). Significant reductions from rest in VolFlow and %Rel were first observed at 50% LOP and 40% LOP, respectively. VolFlow at 80% LOP, a commonly used occlusion pressure in the legs, was not significantly different from 60% (p = .88), 70% (p = .20), or 90% (p = 1.00) LOP. Findings indicate a minimal threshold pressure of 50%LOP may be required to elicit a significant decrease in arterial blood flow at rest when utilizing the 11.5cm Delfi PTSII tourniquet system.
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PURPOSE: The purpose of this study was to examine the time course of health, fitness, and occupational performance changes in firefighter recruits across a fire academy. METHODS: Nineteen recruits (24.9 ± 4.3 yr; 26.7 ± 3.1 kg·m -2 ) had their body composition, balance, vertical jump (VJ) performance, cardiorespiratory fitness (CRF), upper and lower body strength, hamstrings-to-quadriceps (H/Q) ratio, lower back endurance, and weighted stair climb (SC) performance assessed at the beginning (week 1 [W1]), midpoint (week 15 [W15]), and end (week 30 [W30]) of a fire academy. RESULTS: The fire academy improved body composition, balance, CRF, leg extension strength, and SC performance from W1 to W15 ( P ≤ 0.042) which then plateaued at W30 ( P ≥ 0.314). Leg flexion strength and the H/Q ratio decreased from W1 to W15 ( P ≤ 0.035) and plateaued at W30 ( P ≥ 0.947). Upper body strength was similar at W1 and W15 ( P ≥ 0.999), but decreased at W30 ( P ≤ 0.033). However, no significant changes occurred across the academy for VJ performance or lower back endurance ( P ≥ 0.090). CONCLUSIONS: These findings highlight the positive effect of the academy on body composition, CRF, balance, SC performance, and leg extension strength. However, the decreases in upper body and leg flexion strength, the H/Q ratio, and lack of changes in VJ performance and low back endurance may highlight key areas of need to maximize injury prevention and performance enhancement efforts in the academy. Further, the varied time course of changes may help fire departments identify opportunities to modify exercise programming across their academies.
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Aptidão Cardiorrespiratória , Aptidão Física , Humanos , Teste de Esforço , Exercício Físico , Composição CorporalRESUMO
This study examined the acute effects of high-intensity resistance exercise with blood flow restriction (BFR) on performance and fatigue, metabolic stress, and markers of inflammation (interleukin-6 (IL-6)), muscle damage (myoglobin), angiogenesis (vascular endothelial growth factor (VEGF)). Thirteen resistance-trained participants (four female, 24.8 ± 4.7 years) performed four sets of barbell back-squats (75% 1RM) to failure under two conditions: blood flow restriction (BFR, bilateral 80% occlusion pressure) and control (CTRL). Completed repetitions and pre-post-exercise changes in maximal voluntary isometric contractions, countermovement jump, barbell mean propulsive velocity, and surface electromyography were recorded. Pre-post blood lactate (BLa) and venous blood samples for analysis of IL-6, myoglobin, and VEGF were collected. Ratings of perceived exertion (RPE) and pain were recorded for each set. Fewer repetitions were performed during BFR (25.5 ± 9.6 reps) compared to CTRL (43.4 ± 14.2 reps, p < 0.001), with greater repetitions performed during sets 1, 2, and 4 (p < 0.05) in CTRL. Although RPE between conditions was similar across all sets (p > 0.05), pain was greater in BFR across all sets (p < 0.05). Post-exercise fatigue was comparable between conditions. BLa was significantly greater in CTRL compared to BFR at two minutes (p = 0.001) but not four minutes post-exercise (p = 0.063). IL-6 was significantly elevated following BFR (p = 0.011). Comparable increases in myoglobin (p > 0.05) and no changes in VEGF were observed (p > 0.05). BFR increases the rate of muscular fatigue during high-intensity resistance exercise and acutely enhances IL-6 response, with significantly less total work performed, but increases pain perception, limiting implementation.
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Treinamento Resistido , Fator A de Crescimento do Endotélio Vascular , Feminino , Humanos , Fadiga , Interleucina-6 , Músculo Esquelético/fisiologia , Mioglobina , Dor , Fluxo Sanguíneo Regional/fisiologia , MasculinoRESUMO
Upper body (UB) strength is important for occupational tasks and injury prevention in law enforcement officers (LEOs). Portable, reliable, and cost-effective assessments are needed to examine UB strength among LEOs in field settings. The purpose of this study was to examine the test-retest reliability and minimum difference (MD) values of a novel and portable isometric upright row assessment in probation officers. Thirty certified probation officers (18 women; age = 38.9 ± 9.0 years, body mass = 98.8 ± 27.1 kg, stature = 171.4 ± 14.0 cm) volunteered for this investigation. Testing occurred on-site across two sessions (2-5 days apart). Participants stood upon an aluminum plate with a chain attached to a handle and dynamometer. They grasped the handle with a pronated grip, two cm below the umbilicus, and performed three isometric maximal voluntary contractions. Intraclass correlation coefficient (ICC2,1), standard error of the measurement (SEM), and MD values were calculated. Results indicated no significant systematic error (p = 0.080) across sessions. The ICC2,1, SEM, and MD values for UB strength were 0.984, 27.20 N (4.1% of the mean), and 75.38 N (11.3% of the mean), respectively. These data suggest this isometric upright row assessment is a reliable, portable, and cost-effective measure of UB strength to assess and monitor LEOs in field settings.
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Contração Isométrica , Polícia , Humanos , Feminino , Adulto , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Voluntários , Força MuscularRESUMO
Analysis of Brightness-mode ultrasound-captured fascicle angle (FA) and fascicle length (FL) can be completed manually with computer-based programs or by automated programs. Insufficient data exists regarding reliability and accuracy of automated tools. Therefore, the purpose of this study was to determine the test-retest reliability of automatic and manual ultrasound analyses, while determining accuracy of the automatic tool against the manual equivalent. Twenty-three participants (mean ± SD; age = 24 ± 4 years; height = 172.2 ± 10.5 cm; body mass = 73.1 ± 16.1 kg) completed one laboratory visit consisting of two trials where vastus lateralis muscle architecture was assessed with ultrasound. Images were taken at both lower (10 MHz) and higher frequency (12 MHz). Images were analyzed manually in an open-source imaging program and automatically using a separate open-source macro function. Test-retest reliability statistics were calculated for automatic and manual analyses. Accuracy was determined with validity statistics and were calculated for automatic analyses. The results show that manual ultrasound analyses for FA and FL for both lower and higher frequency displayed good reliability (ICC2,1 = 0.75-0.86). However, automatic ultrasound analyses for FA and FL revealed moderate reliability (ICC2,1 = 0.61-0.72) for the lower frequency images and poor reliability (ICC2,1 = 0.16-0.27) for higher frequency images. When assessed against manual techniques, automatic analyses presented greater total error (TE) and standard error of the estimate (SEE) for FA at lower frequency (constant error (CE) = -3.91°, TE = 5.57°, SEE = 3.45°) than higher (CE = -2.78°, TE = -4.54°, SEE = 2.45°). For FL, the higher frequency error (CE = 0.92 cm, TE = 2.12 cm, SEE = 1.15 cm) was similar to lower frequency error (CE = 1.98 cm, TE = 3.66 cm, SEE = 1.57 cm). The findings overall show that manual analyses had good reliability and low absolute error, while demonstrating the automated counterpart had poor to moderate reliability and large errors in analyses. These findings may be impactful as they highlight the good reliability and low error associated with manually analyzed ultrasound images and validate a novel automatic tool for analyzing ultrasound images. Future work should focus on improving reliability and decreasing error in automated image analysis tools. Automated tools are promising for the field as they eliminate biases between analysts and may be more time efficient than manual techniques.
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Processamento de Imagem Assistida por Computador , Músculo Quadríceps , Humanos , Adulto Jovem , Adulto , Reprodutibilidade dos Testes , Ultrassonografia/métodos , Processamento de Imagem Assistida por Computador/métodos , SoftwareRESUMO
OBJECTIVE: Although workload monitoring is commonly used in athletic settings to mitigate injury risk, we are unaware of previous studies examining its feasibility among firefighters. METHODS: Nineteen firefighter recruits completed a short online workload survey at the end of each training day (Monday-Friday) for 26 weeks during the academy. A modified System Usability Scale was provided at midtesting (3 months into the academy) and posttesting (end of the academy). RESULTS: The recruits perceived the survey to be user-friendly throughout the academy (83.6 ± 13.6). However, questions 1 (survey frequency) and 6 (survey consistency) decreased and increased from midtesting to posttesting, respectively. Adherence was overall poor, decreasing from midtesting to posttesting. CONCLUSIONS: Our findings suggest that workload monitoring is a user-friendly tool within tactical populations; however, future research should consider optimal survey frequency to enhance compliance.
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Bombeiros , Humanos , Inquéritos e Questionários , Carga de TrabalhoRESUMO
The purpose of this study was to determine if segmental bioelectrical impedance spectroscopy characteristic frequency (fc) and phase angle (Pa) were reflective of differences in quadriceps muscle size and quality, respectively, in normal weight and obese older men, and to assess the impact of hydration status on these measurements. Forty-one healthy older men volunteered for this study and were recruited by age (65-74 years) and two body mass index groups: normal weight and obese. Participants visited the laboratory on one occasion where they underwent a hydration status assessment via urine specific gravity, a percent body fat assessment via dual-energy X-ray absorptiometry, a segmental bioelectrical impedance spectroscopy thigh assessment to determine fc and Pa, and resting ultrasonography to assess superficial quadriceps cross-sectional area and echo intensity as a proxy for muscle quality. Urine specific gravity was not different between the groups (P = 0.116); however, echo intensity, cross-sectional area, and percent body fat were greater in the obese group (P < 0.001), and both fc and Pa were greater in the normal weight group (P < 0.001). Larger muscle cross-sectional area was associated with lower fc (r = -0.597, P < 0.001), but was not associated with Pa (P = 0.469). Poorer muscle quality (higher echo intensity) was associated with lower Pa (r = -0.765, P < 0.001), but not associated with fc (P = 0.244). There was no association between fc and Pa (P = 0.449). All group differences and associations remained unchanged after controlling for urine specific gravity. Segmental bioelectrical impedance spectroscopy may offer an inexpensive, time efficient, and portable assessment of quadriceps muscle size and quality in older men.
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Composição Corporal , Obesidade , Absorciometria de Fóton , Idoso , Composição Corporal/fisiologia , Impedância Elétrica , Humanos , Masculino , Músculo Quadríceps/diagnóstico por imagem , Análise EspectralRESUMO
This study examined the influence of muscle activation and motor unit number estimation (MUNE) on early phase voluntary rate of torque development (RTD) in younger (YM) and older (OM) men. Thirty-two YM (n = 17; Age = 22 yrs) and OM (n = 15; Age = 74 yrs) volunteered to participate in this study. Early phase RTD (first 50 ms of a rapid isometric contraction; RTD50) and normalized surface electromyography (first 50 ms of muscle excitation; nEMG50) were recorded from the right quadricep muscle group. MUNE was examined from the right vastus lateralis. Multiple linear regression analyses revealed that nEMG50 had a significant effect on RTD50 independent of age group (p ≤ 0.001). nEMG50 had a significant effect on RTD50 in the OM group (p = 0.037). MUNE had no effect on RTD50 independent of age. Older adults may depend more on muscle activation at contraction onset of early phase RTD compared to younger adults.
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Envelhecimento , Músculo Esquelético , Adulto , Idoso , Envelhecimento/fisiologia , Eletromiografia , Humanos , Contração Isométrica/fisiologia , Masculino , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Torque , Adulto JovemRESUMO
PURPOSE: This study examined worker characteristics and behaviors and the perceived importance of job-related tasks associated with the willingness to perform a proposed probation officer physical ability test (PROPAT). METHODS: North Carolina probation officers (N = 1213, 46.2% female, 39.8 ± 10.1 yr, 30.7 ± 6.6 kg·m-2) completed a survey including demographics, health history, and job-related tasks. A multivariable logistic regression model estimated the odds of being willing to perform the PROPAT. Adjusted odds ratios (ORadjusted) with 95% confidence intervals (CI) were calculated, with those excluding 1.00 deemed statistically significant. RESULTS: The majority (72%) of probation officers were willing to perform the PROPAT. Being male (compared with female) (ORadjusted = 1.50, 95% CI = 1.12-2.02) and having moderate (ORadjusted = 1.51, 95% CI = 1.10-2.08) and high physical activity status (ORadjusted = 2.89, 95% CI = 1.97-4.28) (compared with low) increased the odds of being willing to perform the PROPAT. Additionally, reporting a greater importance of tasks, including running to pursue a suspect (TASKRUN, 1-unit increase, ORadjusted = 1.25, 95% CI = 1.10-1.43) and dragging an unresisting person (TASKDRAG, 1-unit increase, ORadjusted = 1.16, 95% CI = 1.01-1.32), increased the odds of being willing to perform the PROPAT. Increasing age (1-yr increase, ORadjusted = 0.96, 95% CI = 0.94-0.98), class II (ORadjusted = 0.45, 95% CI = 0.28-0.71) and class III obesity (compared with normal weight, ORadjusted = 0.55, 95% CI = 0.32-0.93), and a previous musculoskeletal injury (ORadjusted = 0.57, 95% CI = 0.35-0.93) all decreased the odds of being willing to perform the PROPAT. CONCLUSIONS: These results suggest being older, previously injured, obese (body mass index ≥ 35 kg·m-2), and less active is associated with being less willing to participate in the PROPAT, whereas males and reporting a higher importance of the TASKRUN and TASKDRAG activities is associated with being more willing to participate in the PROPAT. Departments can use these findings to identify feasible strategies (e.g., education and physical training) to improve the implementation of physical employment standards.
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Atitude Frente a Saúde , Avaliação de Desempenho Profissional/métodos , Emprego/normas , Comportamentos Relacionados com a Saúde , Aplicação da Lei , Seleção de Pessoal/métodos , Aptidão Física , Adulto , Avaliação de Desempenho Profissional/normas , Emprego/psicologia , Feminino , Humanos , Satisfação no Emprego , Masculino , Pessoa de Meia-Idade , North Carolina , Razão de Chances , Seleção de Pessoal/normas , Segurança/normasRESUMO
The purpose of this study was to examine the influence of repeated bouts of shiftwork on lower extremity maximal and rapid strength and reaction time in career firefighters. Thirty-five firefighters (3 females; 34.3 ± 9.1 years) performed a psychomotor vigilance test (PVT) and reactive maximal isometric strength assessment prior to and following a full shift rotation (three 24-hr on-off shifts). Reaction time (RT), maximal, absolute and normalised rapid strength (50, 100, 150, 200 ms), and PVT measures were assessed on-site. Separate linear regression models were used to evaluate the POST-PRE change in variables adjusted for BMI, age, sleep, and call duration. Early (50 ms) absolute rapid strength was the only variable significantly reduced (-25.9%; p = 0.031) following the full shift rotation. Our findings indicate that early rapid strength may be a sensitive measure in detecting work-related fatigue, despite minimal changes in sleep between work and non-work nights and a low call duration. Practitioner summary: We examined the impact of repeated shiftwork on changes in reaction time and neuromuscular function. Early rapid strength was a sensitive, portable lab assessment that feasibly measured work-related fatigue in career firefighters. Interventions that mitigate work-related fatigue may be impactful at preventing falls and/or risk of musculoskeletal injury.
Assuntos
Bombeiros , Tolerância ao Trabalho Programado , Fadiga , Feminino , Humanos , Tempo de Reação , Sono , VigíliaRESUMO
PURPOSE: Although firefighters are required to perform various high-intensity critically essential tasks, the influence of neuromuscular function on firefighter occupational performance is unclear. The primary aim of the current study was to identify the key neuromuscular determinants of stair climb (SC) performance in firefighters. METHODS: Leg extension isometric peak torque (PT), peak power (PP), torque steadiness at 10% (Steadiness10%) and 50% (Steadiness50%) of PT, fatigability following 30 repeated isotonic concentric contractions at 40% of PT, percent body fat (%BF), and a weighted and timed SC task were examined in 41 (age: 32.3 ± 8.2 yrs; %BF: 24.1 ± 7.9%) male career firefighters. RESULTS: Faster SC times (74.7 ± 13.4 s) were associated with greater PT and PP, less fatigability, younger age, and lower %BF (r = -0.530-0.629; P ≤ 0.014), but not Steadiness10% or Steadiness50% (P ≥ 0.193). Stepwise regression analyses indicated that PP and Steadiness50% were the strongest predictors of SC time (R2 = 0.442, P < 0.001). However, when age and %BF were included in the model, these variables became the only significant predictors of SC time (R2 = 0.521, P < 0.001) due to age and %BF being collectively associated with all the neuromuscular variables (excluding Steadiness10%). CONCLUSIONS: Lower extremity neuromuscular function, specifically PP and steadiness, and %BF are important modifiable predictors of firefighter SC performance, which becomes increasingly important in aging firefighters.