Physiological Responses to Firefighting in Extreme Temperatures Do Not Compare to Firefighting in Temperate Conditions

Validity of heart rate derived core temperature estimation during simulated firefighting tasks

Rectal core temperature monitoring can help fire services mitigate heat injury but can be invasive and impractical. EQ02 + LifeMonitor provides a non-invasive estimation of core temperature. Therefore, the primary purpose of this study was to determine the validity of the EQ02 + LifeMonitor compared to the gold standard rectal thermometer core temperature assessment, as well as the potential influence of turnout gear on the estimated and physiological strain experienced during these activities. Thirteen participants completed simulated firefighting tasks with and without turnout gear, involving four rounds of a 5-min walk on a treadmill at 2.8 mph/2.5% grade and 20 deadlifts over 5 min in an environmental chamber set to 40.6 °C; 50% humidity. During each trial participants wore both an EQ02 + LifeMonitor and DataTherm II rectal thermometer. The results from the devices were statistically equivalent (p < 0.001), yet there was a statistically significant difference in the value (~ 0.1 °C; p < 0.001). There was a significant effect of devices [p < 0.001] and time [p < 0.001], but no interaction effect [p = 0.70] on core temperature drift. Estimated core temperature was marginally different from that measured via the DataTherm II. The EQ02 on average overestimated core temperature. Heart rate, rating of perceived exertion, and area under the curve of core temperature were significantly elevated due to turnout gear [ps < 0.025], but not core temperature skin temperature, or ventilatory rate [ps > 0.372]. These results suggest the EQ02 + LifeMonitor may be a viable, non-invasive alternative for assessing core temperature compared to rectal temperature monitoring, especially during rigorous, intermittent activities. Turnout gear does however increase heart rate, cumulative core temperature, and perceived exertion. Additionally, the validity of the estimated core temperature is not impacted by the use turnout gear. This is likely due to significant changes in heart rate, which allowed the heart-rate derived estimate of core temperature to remain consistent with changes in DataTherm II rectal temperatures.

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.

Heat tolerance during uncompensable heat stress in men and women wearing firefighter personal protective equipment

Firefighters run a risk of heat strain during occupational tasks. The number of female firefighters has been increasing, but research relevant to this group is still scarce. We aimed to investigate whether there are any sex differences in heat tolerance or physiological responses during uncompensable heat stress while wearing firefighter personal protective equipment. Twelve female (28 ± 7 years, 66 ± 5 kg, 51.7 ± 4.7 mL kg^-1 min^-1) and 12 male (27 ± 7 years, 83 ± 8 kg, 58.8 ± 7.5 mL kg^-1 min^-1) participants performed walking (maximum of 60 min) at 6W·kg^-1, 40 °C, and 14% relative humidity. No differences were observed between groups in heat tolerance, rectal temperature, heart rate, percent body mass loss, thermal sensation, and rate of perceived exertion. Thus, when personnel are selected using gender-neutral physical employment standards, sex is not an independent factor influencing heat tolerance when wearing firefighter personal protective equipment during uncompensable heat stress.

The Validity and Reliability of a Treadmill Test for Structural Firefighter Applicants

OBJECTIVE

This 2-part study evaluated validity and reliability of a treadmill test for structural firefighters.

METHODS

Wearing fire protective ensemble, 260 participants walked at 1.56 m·s-1, completing a 5-min warm-up, an 8-min stage at a 5.71° incline, then graded stages to exhaustion. In Part 2, 21 participants completed the test on 3 separate days under standardized conditions.

RESULTS

Average (±SD) oxygen uptake () during minutes 1-13 was similar to reported values for simulated fire-rescue work. During the 13th min, was consistent with recommendations for firefighters. in Part 2, exercise duration increased between trials 1 and 2 before stabilizing but was consistent.

CONCLUSIONS

Congruence with reported during simulated firefighting and recommendations for confirmed validity. Acceptable test-retest reliability was demonstrated. We conclude that the test is valid and reliable for evaluating cardiorespiratory endurance for firefighting.

Psychophysiological responses of firefighters to day and night rescue interventions

This study aimed 1) to assess the psychophysiological responses throughout a rescue intervention performed during the day and at night and 2) to determine if a vibrating alarm influences these psychophysiological responses at night. Sixteen male firefighters completed a simulated intervention under three different conditions: 1) during the day with a sound alarm signal (Day_SA), 2) during the night with a sound alarm signal (Night_SA), 3) during the night with a vibrating alarm signal (Night_VA). Cardiovascular and psychological stress were recorded throughout the interventions. During the alarm signal, HR reactivity was greater in Night_SA than in Day_SA (p < 0.01). Parasympathetic reactivation and self-confidence were significantly lower in Night_SA than in Day_SA (p < 0.05). HR reactivity was decreased in Night_VA in comparison to Night_SA (p < 0.05). Overall, the rescue intervention had a greater impact on the psychophysiological variables during the night than during the day, and the type of alarm had a minor effect.

Impact of Time Restricted Feeding on Fitness Variables in Professional Resistance Trained Firefighters

Firefighters are at an elevated risk for cardiometabolic disease and sudden cardiac death due to physiological and psychological stressors. Research suggests time restricted feeding (TRF) may improve health and performance variables.

OBJECTIVE

This study investigated the effects of a 7-week TRF (14-hour fasting:10-hour eating window) on fitness variables related to physical health and performance among professional, resistance-trained firefighters.

METHODS

Several fitness variables were assessed pre- and post-TRF intervention.

RESULTS

Relative and absolute ventilatory threshold (VT) increased (P < 0.05), relative and absolute , decreased (P < 0.05), and muscular strength, endurance, and power were not affected pre- versus post-intervention.

CONCLUSION

Although , decreased, all other performance variables were not negatively impacted by TRF. Improvements in VT may be associated with improvements to markers of endurance exercise performance in firefighters, but more data are needed to confirm this hypothesis.

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.

Qualitative Assessment of Barriers and Ideal Wellness Programming Among Rural Firefighters

OBJECTIVE

The purpose of this study was to determine and assess the perceived physical and psychosocial barriers to, and the constitution of, ideal health and wellness programming among rural firefighters.

METHODS

Open-ended, semi-structured interviews were conducted and recorded on 40 rural, structural firefighters. Responses to each question were qualitatively analyzed to determine themes.

RESULTS

Several themes emerged in regards to the physical and psychosocial stressors of the profession. Three themes emerged relating to the self-perceived barriers to overall health and wellness. There was also agreement in the components of an "ideal" workplace health and wellness program to help overcome perceived barriers.

CONCLUSIONS

The themes that emerged from the interviews with this population are similar to firefighters who work in a more urban area. This indicates that the stressors and barriers firefighters face may be occupation, and not location, driven.