During firefighting, thermoregulation is challenged due to a combination of harsh environmental conditions, high metabolic rates and personal protective clothing (PPC). Consequently, investigations of thermoregulation in firefighters should not only consider climate and exercise intensity, but technical properties of textiles too. Therefore, laboratory textile performance simulations may provide additional insights into textile-dependent thermoregulatory responses to exercise. In order to investigate the thermo-physiological relevance of textile properties and to test how different garments affect thermoregulation at different exercise intensities, we analyzed the results of a standard laboratory test and human subject trials by relating functional properties of textiles to thermo-physiological responses. Ten professional, healthy, male firefighters (age: 43 ± 6 y, weight: 84.3 ± 10.3kg, height: 1.79 ± 0.05m) performed low and moderate intensity exercise wearing garments previously evaluated with a sweating torso system to characterize thermal and evaporative properties. Functional properties of PPC and the control garment differed markedly. Consequently, skin temperature was higher using PPC at both exercise intensities (low: 36.27 ± 0.32 versus 36.75 ± 0.15℃, P < 0.05; moderate: 36.53 ± 0.34 versus 37.18 ± 0.23℃, P < 0.001), while core body temperature was only higher for PPC at moderate (37.54 ± 0.24 versus 37.83 ± 0.27℃, P < 0.05), but not low-intensity exercise (37.26 ± 0.21 versus 37.21 ± 0.19, P = 0.685). Differences in thermal and evaporative properties between textiles are reflected in thermo-physiological responses during human subject trials. However, an appropriate exercise intensity has to be chosen in order to challenge textile performance during exercise tests.

It is currently unclear how the assembly of different fabric layers of personal protective clothing (PPC) contributes to differences in thermal comfort among garments. Therefore, we used two different approaches to investigate the effect of PPC on body heat dissipation: a technical characterization of textiles (using sweating Torso methodology) and thermo-physiological wearing trials. We hypothesized that the technical characterization provides a similar outcome compared to the wearing trials and, thus, proves to have high thermo-physiological relevance. Thirteen different PPC were investigated using the sweating Torso methodology. Three out of these thirteen were then selected for inclusion in a series of human subject trials in a hot environment. Results from human trials and Torso testing were related to each other. The thermal and evaporative properties of the selected PPC typically differed and effects were observed for the thermo-physiological responses of human study participants. Differences in Torso surface temperature of up to 9℃ and moisture accumulation in the protective clothing systems of up to 184 g·m–2 were detected using the sweating Torso methodology. Moderate intensity exercise with the human study participants induced textile-dependent differences of up to 0.9 ± 0.2℃ (P < 0.001) and 1.2 ± 0.2℃ (P = 0.008) for excessive core body and excessive skin temperature, respectively. Using the sweating Torso methodology, physiologically relevant differences in textile performance could be detected among different PPC. Consequently, sweating Torso is a relevant tool to gain insight into human thermo-physiological responses to different PPC with similar end-use based on their dry and wet heat transfer characteristics.

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