Introduction: Firefighting is one of the most strenuous and dangerous occupations in the community. Training Officers are senior firefighters who take on the preparation and education of their fellow firefighters. One of the Training Officers’ tasks is structured live-fire training. During live-fire training, they are exposed to the stress of fire and high heat multiple times per day. In spite of this issue, there is no research focusing on Training Officers during the live-fire training evolution. Purpose: The present study was a pilot study to measure the stress experienced in the live-fire training and possibly reduce this stress by managing hydration status. Method: Five training officers from Boise Fire Department participated in the live-fire training. The experimental variables during the live-fire training were relative workload, measured via air consumption rate (ACR), heart rate (HR), and blood lactate; thermal stress measured via core temperature, plasma volume (PV), and body weight. In addition, a hydration protocol to compare between water and high-sodium electrolyte solution was executed to determine the potential effect on reducing the stress response. Laboratory data collected to establish individual fitness levels and determine live-fire training intensity included lactate threshold (maximal oxygen consumption (O2max) test) and body composition. Means ± SD were calculated for anthropometric data, lactate-threshold O2max test, and all variables measured in the live-fire training. ACR and HR were compared with percent of oxygen uptake reserve (%O2R) and percent of heart rate reserve (%HRR) during the evolutions, respectively, expecting more than moderate intensity (≥ 40%). One-tailed one-sample t-test was used for blood lactate comparing with OBLA, expecting more than 4.0 mmol/L post-evolution. Paired t-tests were used to compare core temperature between baseline and the peak, PV between baseline and the lowest, and body weight between the pre- and post-training, as well as used to compare between control and treatment conditions in mean ACR, mean HR, mean blood lactate, core temperature change from baseline to the peak, PV change from baseline to the lowest, and body weight change from the pre- to post-training (p u3c 0.05). Results: The training evolutions significantly increased core temperature (p u3c 0.05). The other variables (ACR, HR, lactate, PV and body weight) did not reach significant differences. In addition, there was no significant difference between the control and treatment conditions for any variables. Along with the hydration status, urine specific gravity showed the training officers well-managed their hydration from the pre- to post-training and there was no significant difference between the control and treatment conditions. Conclusion: The extremely hot environment was a greater stress than the physical exertion during structured live-fire training, greatly affecting core temperature. A high-sodium electrolyte solution did not directly affect the work stress or performance. Yet, it could reduce the degree of hydration and excretion demands, which contribute to physiologic stress and increase training officer comfort.
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