T. Burden, J. Long, K. Christison, S. Gurney, J. Knight, M. Martin, S. Hilden, C. Dumke, FACSM

University of Montana, Missoula, MT

Uncompensable heat gain from wildland firefighter (WLFF) personal protective equipment decreases the physiological tolerance one can endure while exercising in the heat. PURPOSE: To identify performance differences in simulated working conditions wearing traditional non-vented WLFF helmet (H) compared to a vented helmet (VH). METHODS: Ten male subjects with a VO2maxof 59.8 ± 3.6 ml/kg/min walked for two 180-minute trials (at 3.5 mph, 5% grade) in a heat chamber (35C and 30% relative humidity). Trials started with a 10 minute chamber acclimation period, followed by three intervals of 50 minutes of exercise and 10 minutes of rest, followed by a performance test to exhaustion. Subjects were provided with 5 ml of water/kg of body weight every 30 minutes. Separated by a two-week washout, subjects repeated the trial with randomly ordered helmets. Each trial measured % dehydration, sweat rate, and performance (PKJ). Peak helmet temperature, perceived head heat (PVAS), helmet humidity (PHH), heart rate, physiological strain index, rating of perceived exertion, core temperature (PTc), and skin temperature were collected during the performance test. Paired samples t-tests compared differences between the H and VH trials RESULTS: All 10 subjects were able to finish both trials. Sweat rate nor percent dehydration did not differ between trials. Performance was significantly greater in VH (95.9±10.3 KJ H vs. 109.3±8.5 KJ VH). PHH (47.3±1.4% H vs. 45.0±1.3% VH) and PVAS (108.8±9.2 mm H vs. 91.5±9.9 mm VH) were all significant (pc (38.32±0.11C H v. 38.18±0.10C VH; p≤0.08) existed. CONCLUSION: These data (PHH, PVAS, and PKJ) suggest that a vented helmet could result in greater performance for wildland firefighters. While PTcdid not reach significance, a statistical trend suggests that a vented helmet could improve heat dissipation for the body. The current design of the WLFF helmet may contribute to heat gain, reduced performance, and heat related illnesses for the working WLFF.

Supported by the USFS (18-CR-11138100-005).

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