Heat Acclimation Program for Firefighters Reduced Heat Stress and Improved Thermal Sensation and Thermal Comfort during Exercise Wearing a Firefighting Suit

Introduction Firefighters are exposed to an excessive heat stress and at the risk of heat‐related disorders and heat stroke during firefighting because they are wearing a firefighting suit with high insulation. Heat acclimation for firefighters would reduce the heat stress and the risk of heat‐related disorders during firefighting. Typical programs of heat acclimation require a few hours per day for 5 to 10 consecutive days and an artificial hot environment, those are unrealistic and impossible for them during their daily duty. In this study, we tested whether a heat acclimation program for firefighters performed in fire stations during daily duty with a simple exercise protocol wearing thermal insulation clothes would reduce heat stress and improve thermal sensation (TS) and thermal comfort (TC) during exercise wearing with a firefighting suit. Methods Twenty male active firefighters (age; 20–50 years old) underwent a ~1‐month heat acclimation program (interval stair stepping exercise for 32 min, 4 sets of 5 min at high‐intensity – 3 min at low‐intensity, ~9 times/month) wearing a rain coat (9 subjects, RC group) or a firefighting suit (11 subjects, FS group) in addition to their regular training at their fire stations. Before and after intervention, they underwent a graded walking test (1.5, 3.0, 4.5, and 6.0 km/hour for 9 min each with 5% grade) wearing a firefighting suit in a climate chamber (25°C ambient temperature, 40% relative humidity). Heart rate (HR), esophageal (T es ) and mean skin temperatures (T sk ), skin blood flow (SkBF) and sweat rate (SR) at chest were continuously monitored and TS and TC were determined every minute. When T es reached 38.5 °C, test was terminated before the end. Results After intervention, at rest, T es and T sk decreased and TS improved only in FS group, while TC improved in both groups (all, p < 0.05). In addition, T es , T sk , and also HR decreased and TS and TC improved during exercise in both groups (all, p < 0.05), though the reduction after intervention in these variables were prominent in FS group compared with RC group. SkBF and SR at chest in response to increased T es were enhanced more in FS group than RC group. Conclusions The heat acclimation program performed in fire stations during daily duty in firefighters wearing thermal insulation clothes reduced heat stress with enhanced thermoregulatory responses and improve thermal sensation and comfort during exercise wearing a firefighting suit. Clothes that have higher thermal insulation (firefighting suit) would be more effective for the heat acclimation program. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .