Neuromuscular determinants of simulated occupational performance in career firefighters

Firefighters' muscle activity change during firefighting training program

BACKGROUND

Research on muscle activity to reduce injuries during firefighting training has getting increasing attention.

OBJECTIVE

The purpose of this study was to assess the activity changes in nine muscles of firefighters during the seven firefighting training programs, and to analyze the influence of different firefighting training programs on muscle activity.

METHODS

Ten healthy male firefighters were recruited to measure the field surface electromyographic activities (including the percentage of Maximum Voluntary Contraction electromyography (% MVC) and the integrated electromyography value (iEMG)) during all the firefighting training programs.

RESULTS

The results showed that the electromyographic activity of gastrocnemius (GA) was stronger in climbing the hooked ladder and climbing the six-meter long ladder training programs. Arms, shoulders, and lower limb muscles were more activated, myoelectric activities were more intense, and fatigue in these areas was more likely to occur during climbing five-story building with loads. Compared with other muscles, erector spine (ES) had a higher degree of activation during different postures of water shooting. The Borg scale scores of shoulders, trunk, thighs and calves were also higher.

CONCLUSION

After completing all training programs, GA, tibialis anterior (TA), trapezius (TR), and ES were strongly activated, and all muscles had obvious force. The % MVC and iEMG analyses correspond well with the Borg Scale score. The results can provide certain reference for reducing the musculoskeletal injury of firefighters, carrying out scientific training and formulating effective injury prevention measures for them.

Characteristics of slow and fast performers on a firefighter air consumption test

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).

Strategies for Improving Firefighter Health On-Shift: A Review

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.

The impact of inter-limb leg lean tissue mass asymmetry on stair climb performance in career firefighters

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.

Climbing the Ranks: A Study of Firefighter Health Disparities

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.

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.

Body Composition Is Related to Maximal Effort Treadmill Test Time in Firefighters

Firefighting tasks may require near maximal levels of cardiorespiratory fitness. Previous research has indicated that body fat percentage (BF%) and aerobic capacity (VO_2peak) are related to the performance of firefighting tasks. Since a standard submaximal treadmill test for firefighters is terminated at 85% of maximal heart rate (MHR), key performance information relating to maximal cardiorespiratory effort may not be measured in a submaximal test. The purpose of this study was to examine the relationships between body composition and time spent running at intensities greater that 85% MHR. Height, weight, body mass index (BMI; kg/m²), BF%, MHR (bpm), VO_2peak (mL/kg/min), predicted VO_2peak (P-VO_2peak; mL/kg/min), submaximal treadmill test time (WFI_sub Test Time; min), and maximal treadmill test time (WFI_max Test Time; min) were collected in fifteen active-duty firefighters. The results indicated that significant relationships (p < 0.05) existed between BF% and VO_2peak, BF% and WFI_max Test Time, BF% and T_diff, and VO_2peak and WFI_max Test Time. P-VO_2peak was not significantly different than VO_2peak, and the WFI_max Test Time was significantly longer than the WFI_sub Test Time. These results indicate that a submaximal treadmill test may reasonably predict VO_2peak, but key information about physiological work at intensities greater than 85% MHR may be missed when using submaximal effort tests.

Effects of Cardiovascular Disease Risk Factors, Musculoskeletal Health, and Physical Fitness on Occupational Performance in Firefighters-A Systematic Review and Meta-Analysis

Background: Firefighting is a strenuous occupation, which necessitates that firefighters stay in good physical condition and maintain adequate cardiovascular and musculoskeletal fitness to perform their duties with minimal health and safety risks. The aim of this review is to determine the effects of cardiovascular disease risk factors, musculoskeletal health, and physical fitness on the occupational performance of firefighters. Methods: PubMed/Medline, SCOPUS, Web of Science, EBSCOHost, and ScienceDirect were searched without time-restriction. The appraisal tool for cross-sectional studies and the Critical Appraisal Skills Programme toolkit were used to conduct the methodological assessment. Data were analyzed using Review Manager 5.3, and MedCalc^® statistical software. Results: Age had a moderate effect on occupational performance (Z = 5.15, p < 0.001), whereas gender had a large effect size on occupational performance (Z = 4.24, p < 0.001). A significant moderate negative correlation was found between cardiorespiratory fitness and occupational performance (R = -0.584, p < 0.001). Significant low negative correlations were found between upper body endurance (R = -0.344, p < 0.001), abdominal endurance (R = -0.308, p < 0.001), grip strength (R = -0.421, p < 0.001), upper body strength (R = -0.318, p < 0.001), and lower body strength (R = -0.216, p = 0.020) and occupational performance. Conclusions: Aged firefighters with poor body composition and lower levels of physical fitness performed worse on all occupational performance tasks.