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The rate of body heat storage in subjects wearing a prototype firefighter ensemble.

Williams-WJ; Roberge-RJ; Coca-A; Powell-JB; Kim-J-H
Med Sci Sports Exerc 2010 May; 42(5)(Suppl 1):767
Firefighter ensembles impose significant heat stress on the wearer (both metabolic and environmental). Heat stress can negatively impact the physical performance and health status of the wearer. PURPOSE: To compare the rate of body heat storage in response to wearing a prototype firefighter ensemble with self-contained breathing apparatus (PFE + SCBA; total weight - 21.21 +/- 0.37 kg) exhaust gas re-routed into the ensemble to a standard ensemble (SE + SCBA; total weight - 19.96 +/- 0.38 kg) during exercise. METHODS: Ten healthy subjects (7 men and 3 women) participated in this study. Subjects performed treadmill exercise at 50%VO2max in an environmental chamber (22 degrees C, 50% RH) while wearing the PFE or SE. Heart rate (HR, beats·min-1), skin temp (Tsk), core body temp (Tc), and exercise duration (ExD) were recorded before and during treadmill exercise. The rate of body heat storage (S; W) was calculated using thermometric methods. RESULTS: After treadmill exercise, the increased HR in SE was lower compared to PFE (73.8 +/- 12.7 vs. 87.6 +/- 13.5; p=0.014) and the increase in Tsk in SE was lower compared to PFE (2.4 +/- 0.55 degrees C vs. 2.92 +/- 0.79 degrees C; p=0.008). Although there was no significant difference in Tc between SE and PFE, increase in mean body temp (DTb = 0.79 Tc + 0.21 Tsk) was greater in PFE (1.0 +/- 0.16 degrees C) than in SE (0.85 +/- 0.11 degrees C) (p=0.002). The rate of body heat storage [S (W) = (body mass; kg) × (DTb in degrees C·min-1) × (0.965 W·degrees C·kg-1)] during exercise was lower in SE (181.5 +/- 39.66 W) compared to PFE (215.5 +/- 56.83 W) after treadmill exercise (p=0.006). ExD was less in PFE (23.65 +/- 3.95 min) compared to SE (28.59 +/- 7.45 min) (p=0.005). CONCLUSION: The data suggest that, in spite of the air flow re-routed to the ensemble from the exhaust gases of the SCBA, the rate of body heat storage (S; W) imposed by the PFE was greater than from the SE. This is supported by the increase in HR, Tsk, Tb, and the decrease in ExD in subjects wearing the PFE compared to SE. Thus, the air flow to the PFE did not reduce the physiological "burden" compared to the SE.
Biological-factors; Body-protection; Body-temperature; Exposure-levels; Fire-fighters; Fire-protection-equipment; Heat-acclimatization; Heat-conduction; Heat-exposure; Heat-regulation; Heat-tolerance; Laboratory-testing; Men; Physical-capacity; Physical-reactions; Physical-stress; Physiological-effects; Physiological-factors; Physiological-fatigue; Physiological-measurements; Physiological-response; Physiological-testing; Quantitative-analysis; Quantitative-analysis; Self-contained-breathing-apparatus; Statistical-analysis; Women
Warren J. Williams, National Institute of Occupational Safety and Health, NPPTL, Pittsburgh, PA
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Medicine and Science in Sports and Exercise