Multivariate statistical assessment of predictors of firefighters' muscular and aerobic work capacity

Physiological characteristics predictive of passing military physical employment standard tasks for ground close combat occupations in men and women

Challenges for some women meeting the physical employment standards (PES) for ground close combat (GCC) roles stem from physical fitness and anthropometric characteristics. The purpose of this study was to identify the modifiable and nonmodifiable characteristics predictive of passing GCC-based PES tasks and determine the modifiable characteristics suitable to overcome nonmodifiable limitations. 107 adults (46 women) underwent multiday testing assessing regional and total lean mass (LM), percent body fat (BF%), aerobic capacity (V̇O2peak), strength, power, and PES performance. Predictors with p-value <0.200 were included in stepwise logistic regression analysis or binary logistic regression when outcomes among sexes were insufficient. Relative and absolute arm LM (OR: 4.617-8.522, p < 0.05), leg LM (OR: 2.463, p < 0.05), and upper body power (OR: 2.061, p < 0.05) predicted medicine ball chest throw success. Relative and absolute arm LM (OR: 3.734-11.694, p < 0.05), absolute trunk LM (OR: 2.576, p < 0.05), and leg LM (OR: 2.088, p < 0.05) predicted casualty drag success. Upper body power (OR: 3.910, p < 0.05), absolute trunk LM (OR: 2.387, p < 0.05), leg LM (OR: 2.290, p < 0.05), and total LM (OR: 1.830, p < 0.05) predicted maximum single lift success. Relative and absolute arm LM (OR: 3.488-7.377, p < 0.05), leg LM (OR: 1.965, p < 0.05), and upper body power (OR: 1.957, p < 0.05) predicted water can carry success. %BF (OR: 0.814, p = 0.007), V̇O2peak (OR: 1.160, p = 0.031), and lower body strength (OR: 1.059, p < 0.001) predicted repeated lift and carry success. V̇O2peak (OR: 1.540, p < 0.001) predicted 2-km ruck march success. Modifiable characteristics were the strongest predictors for GCC-based PES task success to warrant their improvement for enhancing PES performance for women.

Physical fitness profile of a large urban fire department: Exploring age and rank dynamics

BACKGROUND

Firefighter physical fitness (PF) plays a crucial role in mitigating health issues and supporting occupational performance. The influence of rank on firefighter PF remains understudied and previous research is often limited by small sample sizes of firefighters volunteering for research studies, potentially biasing results towards fitter firefighters not representative of entire departments.

OBJECTIVE

To examine the PF profile of firefighters in a large urban fire department and the influence of age and rank on PF.

METHODS

Data, including muscular fitness, estimated aerobic capacity (VO2max), and body fat percentage (BF%) measures from 1361 firefighters (90% male; age: 37.4±10.1yrs; 60 recruits, 973 firefighters, 290 lieutenants/captains, 38 chiefs) were analyzed. Correlation and ANCOVAs were conducted to examine the impact of rank on PF while controlling for age. Score distributions were scrutinized to profile the PF of the department.

RESULTS

Age was negatively associated with pull-ups (r = - 0.39), sit-ups (r = - 0.39), and push-ups (r = - 0.32), but positively associated with relative VO2max (r = 0.17) and BF% (r = 0.39). Rank had a statistically significant, but trivial effect size, on pull-ups (p = 0.028, η2 = 0.007) and sit-ups (p = 0.034, η2 = 0.005). Firefighters with lower PF levels were older, had higher BF%, lower fat-free mass, and were a greater proportion of females.

CONCLUSIONS

Firefighters exhibited diverse levels of PF. Age, not rank, appeared to influence firefighters' PF. The findings that firefighters who were older, female, with poorer body composition are more likely to have lower PF levels highlights the need for individualized PF training to enhance occupational performance and health across the fire department.

Physiological demands and physical performance determinants of a new firefighting simulation test

The study aimed to examine physiological responses of firefighters performing a firefighting simulation test (FST) and to determine the relationship between physical fitness parameters and FST performance. Aerobic fitness, muscular strength, muscular endurance, and anaerobic capabilities were evaluated in 37 firefighters (21-profesionals and 16-volunteers firefighters). Furthermore, participants carried out the FST during which we measured performance, respiratory gas exchange, heart rate (HR), perceived exertion and blood lactate concentrations. Males were significantly faster than females for all tasks of the FST (p < 0.01); however, final performance score (16.5 ± 2.9 and 14.5 ± 2.6 points for males and females, respectively), HR (94.0 ± 2.0% and 93.7 ± 2.3% of HRmax) and perceived exertion (8.1 ± 0.9 and 7.1 ± 1.3) were not significantly different. Prediction of FST performance by LASSO regression revealed a model that included mainly aerobic capacity and maximal strength. In conclusion, FST challenged both aerobic and anaerobic energy metabolisms for both males and females and requires various physiological abilities to perform. Practitioner Summary: For the safety of firefighters and victims, firefighters must meet minimum physical requirements. 37 firefighters performed physical tests and a new firefighting test implemented for the recruitment of firefighters in France. The results revealed that this test is strenuous and that performance is associated with cardiorespiratory fitness and muscular strength. Abbreviations: V̇O2: oxygen consumption; V̇CO2: carbon dioxyde production; V̇E: expired ventilation; RER: respiratory exchange ratio; FST: firefighting simulation test; MAS: maximal aerobic speed; HR: heart rate; RPE: rating of perceived exertion; MVC: maximum voluntary contraction; IMTP: isometric mid-thigh pull; TTE: time to exhaustion; Ppeak: peak power; Pmean: mean power; LASSO: least absolute shrinkage and selection operator; La-: blood lactate concentration.

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.

Predicting Firefighters' Physical Ability Test Scores from Anaerobic Fitness Parameters & Mental Toughness Levels

Physical ability test (PAT) evaluates firefighters' (FF) occupational capacity. The contribution of anaerobic systems during PAT and mental toughness (MT) relationship to PAT is unexplored. PAT modeling based on anaerobic fitness (AF), MT, and respective relationships were examined. Fourteen male FFs (Age: 29.0 ± 7.0 years) completed a PAT composed of occupationally-specific tasks in full gear. On a separate day, a series of AF assessments were performed (handgrip-dynamometry: HG; vertical-jump: VJ; Margaria-Kalamen: MK; 300-yard shuttle run: 300YD). MT was evaluated using military training MT inventory (MTMTI) and sports MT questionnaire (SMTQ). We tested the PAT model using multiple backward regression and related correlations coefficients at p < 0.05. A 78% proportion of PAT was explained by AF parameters (F_2,13 = 20.2, <0.05). PAT was significantly correlated with HG (r = -0.71, p < 0.01), VJ (r = -0.73, p < 0.01), MK (r = -0.75, p < 0.01), and with 300YD (r = 0.60, p < 0.05). MT did not demonstrate significant correlation with PAT (p > 0.01). Anaerobic system significantly contributes to PAT performance. FFs should optimize AF training, which would allow for enhanced occupational performance in PAT. Further investigation into psychological determinants of FFs is recommended.

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.

Differences in Stronger Versus Weaker Firefighters in Selected Measures of Power

Firefighters are required to perform a wide array of physically demanding job tasks, such as forcible entry, charged hose advances and victim extractions. An adequate level of muscular strength and power are required to successfully perform these tasks. The purpose of this study is to investigate the differences in stronger and weaker firefighters in measures of power. Archived data for twenty-seven (age = 34.3 ± 7.9 yr, body height = 176.3 ± 7.2 cm, body mass = 89.4 ± 15.7 kg) full-time firefighters were analyzed. Participants were placed into one of two groups [i.e., stronger (HIGH) (n = 13) and weaker (LOW) (n = 14)], based on their relative isometric mid-thigh pull (IMTPr) performance. Power measures included counter-movement jump (CMJ) height, and peak anaerobic power in watts (PAPW). Significant mean score differences were not discovered between HIGH and LOW IMTPr groups on any measures of lower-body power. Moderate positive correlations were observed between IMTP and CMJ (r = .519; p = .01). This study identified significant differences in absolute and relative strength between firefighters who were able to lift at least 2.0× their bodyweight versus those who were not. Additionally, absolute strength (as assessed by the IMTP) was significantly and positively correlated to CMJ height when compared to their weaker counterparts. These findings may provide insight into approaches for improving occupational performance and durability through the physical development of firefighters via strength and conditioning programs which focus on developing absolute strength, relative strength, and power.

Lack of Predictive Power in Commonly Used Tests for Performance in Alpine Skiing

Competitive alpine skiing is a complex sport that requires high physical and technical competence. Testing the physical status of athletes may be important to increase their ability to achieve elite sport-specific performance. This study aimed to investigate the predictive power of the national test battery of the Swedish Olympic Committee (Fysprofilen) and anthropometric variables in the prediction of competitive performance of elite alpine skiers, indicated by Fédération Internationale de Ski points. Data from fourteen Swedish elite female alpine skiers were analyzed using bivariate and multivariate statistical methods. Physiological test results and anthropometric data could not generate significant bivariate or multivariate models for prediction of competitive performance. Multivariate regression (R2) and prediction (Q2) models for Fédération Internationale de Ski Slalom and Giant Slalom rank reached R2=0.27 to 0.43, Q2=+− 0.8 to−0.17, indicating no valid models. The overall interpretation of these and previous findings are that future test batteries must be validated before implemented, and that test results should be treated with caution when it comes to prediction of future competitive results. Applying tests that are not validated against competitive performance risk misleading coaches and training advisors who aim to increase the sports-specific performance of the individual athlete.

Physical Fitness Evaluation of Career Urban and Wildland Firefighters

OBJECTIVE

Examine the physical fitness of career firefighters and compare their results to normative data and suggested standards for their profession.

METHODS

Eighty firefighters completed a body composition analysis, maximal aerobic capacity (VO2max) test, and fitness testing battery, with results compared with normative value tables. Maximal aerobic capacity was correlated to fitness measures and differences between VO2max quartiles were examined.

RESULTS

Twenty-two firefighters met the suggested standard for VO2max. Seventy percent of participants were classified as overweight or obese based on body mass index, while 25% were classified as having either "poor" or "very poor" body fat levels. Firefighters were above average for muscular strength.

CONCLUSION

The firefighters had low aerobic fitness and higher than optimal body fat levels. Training programs may be necessary to assist firefighters in achieving optimal fitness levels.

What do Firefighting Ability Tests Tell Us About Firefighter Physical Fitness? A Systematic Review of the Current Evidence

Fyock-Martin, MB, Erickson, EK, Hautz, AH, Sell, KM, Turnbaugh, BL, Caswell, SV, and Martin, JR. What do firefighting ability tests tell us about firefighter physical fitness? A systematic review of the current evidence. J Strength Cond Res 34(7): 2093-2103, 2020-The firefighting profession is a physiologically demanding occupation. Currently, sudden cardiac deaths account for 40-50% of firefighter job-related deaths, for which, inadequate aerobic fitness (AF) and obesity are established as risk factors. Departments have instituted firefighting physical ability tests (FPATs) as a method of quantifying readiness for occupational-related demands. A systematic review of the current literature examining the correlation between field fitness test performance and FPAT completion times was performed. The search identified 5 studies that met the eligibility criteria. The total number of subjects in the 5 studies was 265 (259 men and 6 women), including 200 professional firefighters (75.5%), 40 volunteer (15.1%), 20 officers (7.5%), and 5 recruits (1.9%). Upper-body strength (UBs) and upper-body endurance (UBe) had the strongest correlation to FPATs (r = -0.31 to -0.66; R = 0.10 to 0.44 and r = -0.27 to -0.61; R = 0.07 to 0.37; p < 0.05, respectively). Two studies suggested that AF has a weak-to-moderate relationship with FPATs (r = 0.38 and r = -0.62). Two studies showed that anaerobic capacity had weak-to-strong correlations with FPATs (r = -0.40 and r = 0.79; R = 0.16 to 0.62; p < 0.05). No studies found a statistically significant correlation between lower-body strength and FPAT performance. Further research is needed to better understand the role of field-based fitness test results on FPAT performance. An annual department-driven multicomponent fitness assessment measuring UBs, UBe, anaerobic capacity, and AF is recommended based on the evidence reviewed.

Physical and Physiological Performance Determinants of a Firefighting Simulation Test

OBJECTIVE

To examine determinants of firefighting simulation test performance.

METHODS

Sixty-eight (63 male; 5 female) firefighters completed a firefighting simulation (eg, equipment carry, casualty evacuation) previously validated to test occupational fitness among UK firefighters. Multiple linear regression methods were used to determine physiological and physical attributes that best predicted completion time.

RESULTS

Mean (±SD) time taken to complete the simulation was 610 (±79) seconds. The prediction model combining absolute cardiorespiratory capacity (L min) and fat mass explained the greatest variance in performance and elicited the least random error (R = 0.765, R = 0.585, standard error of the estimate [SEE]: ±52 seconds). Higher fitness and lower fat mass were associated with faster performance.

CONCLUSIONS

Firefighter simulation test performance is associated with absolute cardiorespiratory fitness and fat mass. Fitter and leaner individuals perform the task more quickly. Work-based interventions should enhance these attributes to promote safe and effective operational performance.

Aerobic Variables for Prediction of Alpine Skiing Performance - A Novel Approach

The aim of this study was to investigate the predictive power of aerobic test results and anthropometric variables on FIS-ranking of junior elite alpine skiers. Results from twenty-three male and female adolescent elite alpine skiers from two seasons were included in the multivariate statistical models. Physical work capacity was determined by V̇O2peak, blood lactate concentration ([HLa]b), and heart rate (HR) during ergometer cycling. Anthropometric variables were body stature, body weight and calculated BMI. No significant correlation between competitive performance and aerobic work capacity or anthropometric data was observed neither in male nor female adolescent skiers. Pre-season physical tests and anthropometric data could therefore not predict end-season FIS-ranking. The best regression (R2) and prediction (Q2) models of FIS slalom (SL) and giant slalom (GS) rank reached R2=0.51 to 0.86, Q2=−0.73 to 0.18, indicating no valid models. This study could not establish V̇O2peak and other included variables as predictors of competitive performance. When combining results from commonly used tests for alpine skiers, and applying multivariate statistical models, investigated tests seems of limited used for athletes, coaches, and ski federations. Performance-specific pre-season tests must be developed and validated for prediction of performance and guidance of exercise training.

Autologous Doping with Cryopreserved Red Blood Cells - Effects on Physical Performance and Detection by Multivariate Statistics

The discovery of erythropoietin (EPO) simplified blood doping in sports, but improved detection methods, for EPO has forced cheating athletes to return to blood transfusion. Autologous blood transfusion with cryopreserved red blood cells (RBCs) is the method of choice, because no valid method exists to accurately detect such event. In endurance sports, it can be estimated that elite athletes improve performance by up to 3% with blood doping, regardless of method. Valid detection methods for autologous blood doping is important to maintain credibility of athletic performances. Recreational male (N = 27) and female (N = 11) athletes served as Transfusion (N = 28) and Control (N = 10) subjects in two different transfusion settings. Hematological variables and physical performance were measured before donation of 450 or 900 mL whole blood, and until four weeks after re-infusion of the cryopreserved RBC fraction. Blood was analyzed for transferrin, iron, Hb, EVF, MCV, MCHC, reticulocytes, leucocytes and EPO. Repeated measures multivariate analysis of variance (MANOVA) and pattern recognition using Principal Component Analysis (PCA) and Orthogonal Projections of Latent Structures (OPLS) discriminant analysis (DA) investigated differences between Control and Transfusion groups over time. Significant increase in performance (15 ± 8%) and VO2max (17 ± 10%) (mean ± SD) could be measured 48 h after RBC re-infusion, and remained increased for up to four weeks in some subjects. In total, 533 blood samples were included in the study (Clean = 220, Transfused = 313). In response to blood transfusion, the largest change in hematological variables occurred 48 h after blood donation, when Control and Transfused groups could be separated with OPLS-DA (R2 = 0.76/Q2 = 0.59). RBC re-infusion resulted in the best model (R2 = 0.40/Q2 = 0.10) at the first sampling point (48 h), predicting one false positive and one false negative. Over all, a 25% and 86% false positives ratio was achieved in two separate trials. In conclusions, autologous re-infusion of RBCs increased VO2max and performance as hypothesized, but hematological profiling by multivariate statistics could not reach the WADA stipulated false positive ratio of <0.001% at any time point investigated. A majority of samples remained within limits of normal individual variation at all times.