Physiological Stress Responses To A Live-fire Training Evolution In Career Firefighters

Firefighters have a physically demanding job that exposes them to many specific and unique stressors, which contribute to cardiovascular disease (CVD) risk (i.e., cardiovascular strain, inflammation, and oxidative stress) or even mortality. At present, the literature lacks data evaluating these physiological stress responses amongst firefighters in any realistic or simulated scenarios, such as a live-fire training evolution (LFTE). Given the elevated risk of premature mortality, there is a critical need to better understand the physiological stress responses to an LFTE. This information could aid in developing nutritional, training, and other various interventions to mitigate stress load and reduce the incidence of CVD among this population. PURPOSE: To assess the physiological stress response to an LFTE among career firefighters. METHODS: Seventy-six (n = 76) career firefighters completed an LFTE. Salivary samples were collected pre, immediately post, and 30-min post the LFTE, and analyzed the following stress markers: α-amylase (AA), secretory immunoglobulin-A (SIgA), and cortisol. One-way repeated measures analysis of variance was used to assess changes over time. Fisher's LSD and Cohen's d effect size calculations were used for Post hoc analysis. RESULTS: Significant main effects for time were found for AA, SIgA, and cortisol (p < 0.001). Fisher’s LSD post hoc analysis found AA, SIgA, and cortisol concentrations were all significantly elevated immediately post LFTE compared to pre (p < 0.0001) and 30-min post (p < 0.0001). Medium to large effect sizes were noted for AA, SIgA, and cortisol with respect to changes pre to immediately post-LFTE (d = 0.838, 0.611, and 0.778, respectively). CONCLUSION: While many studies have shown increased inflammation and oxidative stress, as well as adverse cardiovascular and metabolic responses to firefighting activities, these data provide insight into the physiological stress placed upon a firefighter engaging in fire-suppressive evolutions.