Physiological Stress Responses to a Live-Fire Training Evolution in Career Structural Firefighters

OBJECTIVE

This study assessed firefighters' physiological stress response to a live fire training evolution (LFTE).

METHODS

Seventy-six ( n = 76) firefighters completed an LFTE. Salivary samples were collected pre-, immediately post, and 30-min post-LFTE and analyzed for α-amylase (AA), cortisol (CORT), and secretory immunoglobulin-A (SIgA).

RESULTS

Concentrations of AA, CORT, and SIgA were elevated immediately post LFTE versus pre (P<0.001) and 30-min post (P<0.001). Cohen's d effect size comparing pre and immediately-post means were 0.83, 0.77, and 0.61 for AA, CORT, and SIgA and were 0.54, 0.44, and 0.69 for AA, CORT, and SIgA, comparing immediately-post and 30-min post, respectively.

CONCLUSIONS

These data demonstrate the stress response and activation of the hypothalamic-pituitary-adrenal/sympathetic-adreno-medullar axis and immune system immediately after real-world firefighting operations. Future work is needed to understand the impact of elevated stress biomarkers on firefighter performance and disease risk.

Firefighter Health: A Narrative Review of Occupational Threats and Countermeasures

Structural firefighters are responsible for protecting properties and saving lives during emergency operations. Despite efforts to prepare firefighters for these hazardous occupational demands, the unfortunate reality is that the incidence of health morbidities is increasing within the fire service. Specifically, cardiovascular disease, cancer, and mental health disorders are among the most documented morbidities in firefighters. Pubmed and Google Scholar search engines were used to identify peer-reviewed English language manuscripts that evaluated firefighters' occupational health threats, allostatic factors associated with their occurrence, and evidence-based strategies to mitigate their impact. This narrative review provides fire departments, practitioners, and researchers with evidence-based practices to enhance firefighters' health.

Time Restricted Feeding Reduces Inflammation and Cortisol Response to a Firegrounds Test in Professional Firefighters

OBJECTIVE

Firefighters are at a heightened risk for developing cardiovascular disease. The purpose of this study was to determine if time restricted feeding (TRF) can improve the stress/inflammatory response to a simulated firegrounds test (FGT) in professional firefighters.

METHODS

Thirteen firefighters participated in an 8-week TRF intervention (14:10 [fasting:feeding]) protocol and completed a FGT before and after the intervention. Blood lactate, heart rate, salivary C-reactive protein (CRP), interleukin-6 (IL-6), interleukin 1-β (IL-1β), and cortisol were measured pre and post FGT.

RESULTS

Following TRF, the salivary cortisol response to the FGT was significantly (P < 0.05) reduced. Salivary IL-6 and IL-1β were also significantly lower, and CRP was higher following the intervention.

CONCLUSIONS

These findings demonstrate lower inflammation and reduced stress response to FGT following TRF and may suggest implications in terms of cardiometabolic benefits for firefighters.

Firefighter's Acute Inflammatory Response to Wildfire Suppression

OBJECTIVES

The purpose of this study was to determine the inflammatory response to a 12-hour wildfire suppression shift, in firefighters attending the "Black Saturday" natural disaster.

METHODS

Thirty-eight male volunteer firefighters provided venous blood samples before and after a 12-hour firefighting shift. Pre- to post-shift changes in pro-inflammatory (Interleukin [IL]-1β, IL-2, IL-6, IL-8, IL-12P70, granulocyte macrophage-colony stimulating factor [GM-CSF], tumor necrosis factor-alpha [TNF-α], interferon-gamma [IFNγ]), and anti-inflammatory (IL-4, IL-5, IL-7, IL-10, IL-13) cytokines were measured with paired sample t tests, or Wilcoxon t tests for non-parametric data.

RESULTS

Interleukin (IL)-6 (P = 0.003) and IL-8 (P = 0.017) were significantly increased following 12-hours of wildfire suppression. There was also a significant decrease in IL-10 (P = 0.021).

CONCLUSIONS

The observed acute inflammatory response may have resulted from multiple stressors including physical exertion, thermal strain, or smoke inhalation experienced during the shift, and may be a necessary response for the body to adapt to stressor exposure.

Hot, Tired and Hungry: The Snacking Behaviour and Food Cravings of Firefighters During Multi-Day Simulated Wildfire Suppression

Firefighters are exposed to numerous stressors during wildfire suppression, including working in hot temperatures and sleep restricted conditions. Research has shown that when sleep restricted, individuals choose foods higher in carbohydrates, fat, and sugar, and have increased cravings for calorie dense foods. However, there is currently no research on the combined effect of heat and sleep restriction on snacking behaviour. Conducting secondary analyses from a larger study, the current study aimed to investigate the impact of heat and sleep restriction on snacking behaviour and food cravings. Sixty-six firefighters completed three days of simulated physically demanding firefighting work and were randomly allocated to either the control (n = 18, CON; 19 °C, 8 h sleep opportunity), sleep restricted (n = 16, SR; 19 °C, 4-h sleep opportunity), hot (n = 18, HOT; 33 °C, 8 h sleep opportunity), or hot and sleep restricted (n = 14 HOT + SR; 33 °C, 4-h sleep opportunity) condition. During rest periods firefighters were able to self-select sweet, savoury, or healthy snacks from a ration pack and were asked to rate their hunger, fullness, and cravings every two hours (eating block). Mixed model analyses revealed no difference in total energy intake between conditions, however there was a significant interaction between eating block and condition, with those in the CON, HOT, and HOT + SR condition consuming significantly more energy between 1230 and 1430 compared to the SR condition (p = 0.002). Sleep restriction and heat did not impact feelings of hunger and fullness across the day, and did not lead to greater cravings for snacks, with no differences between conditions. These findings suggest that under various simulated firefighting conditions, it is not the amount of food that differs but the timing of food intake, with those that are required to work in hot conditions while sleep restricted more likely to consume food between 1230 and 1430. This has potential implications for the time of day in which a greater amount of food should be available for firefighters.