Exercise intensity dependent relevance of protective textile properties for human thermo-physiology

Abstract

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.

Fractional Contribution of Wildland Firefighters’ Personal Protective Equipment on Physiological Strain

“…The average temperature increase with this configuration was 1.89 ± 0.48°C, which was twofold greater than the value observed with PPC (0.77 ± 0.34°C). On the contrary, this data was lower than that described in other studies (∼3°C) with structural firefighters ( Sköldström, 1987 ; Smith et al, 1995 ; Bruce-Low et al, 2007 ; Fontana et al, 2017 ) or wearing chemical protective suits ( Wen et al, 2015 ). A T skin above 35°C and a reduced T gi -T skin gradient have been associated with a significant increase in peripheral blood flow, which might limit the subjects’ aerobic performance, even in the absence of dehydration ( Ely et al, 2010 ; Cuddy et al, 2014 ; Faulkner et al, 2015 ).…”

“…However, the increase in core temperature was approximately twice as fast in PPE condition (0.028 ± 0.007°C min -1 ) compared to PPC (0.012 ± 0.004°C min -1 ) or SG (0.011 ± 0.004°C min -1 ). This occurred as a result of the combined effect of the increased metabolic heat production and the heat dissipation limitation associated with the use of PPE, which resulted in a marked situation of uncompensable heat stress ( Table 2 ) and provoked a significantly increased both T gi and T skin ( Figure 2 ) ( Sköldström, 1987 ; Montain et al, 1994 ; Smith et al, 1995 ; Bruce-Low et al, 2007 ; Wen et al, 2015 ; Fontana et al, 2017 ). This fact contributed substantially to reduce the test time to almost half when the subjects wore the PPE.…”

“…This study ( Carballo-Leyenda et al, 2017 ) employed a protocol with a moderate metabolic rate, similar to those previously mentioned ( Budd et al, 1997 ; Den Hartog et al, 2016 ). However, the need to increase the exercise intensity to accentuate the differences between PPC has been reported ( Kofler et al, 2015 ; Fontana et al, 2017 ). Likewise, during wildfire suppression wildland firefighters may perform efforts at high intensities ( Rodríguez-Marroyo et al, 2012 ; Cuddy et al, 2015 ).…”

An integrated approach to develop, validate and operate thermo-physiological human simulator for the development of protective clothing

“…In addition, Torso evaluation system offers a more functional method involving adjustable activity and sweating rate (e.g. cooling dynamics during and after physical activity) 54 , 55 ) . Nevertheless, these instruments and methodologies alone are insufficient for making any sensible judgment on the thermo-physiological effect of the clothing on the wearer 56 ) .…”

“…water vapour permeable and impermeable) and for various activity levels (reclining, sitting, walking, and running). The limited sensitivity of the single-sector human simulator to the functional clothing properties as described by Psikuta et al 22 ) was further investigated by Fontana et al 54 ) and Fontana et al 55 ) . They confirmed the limitation and pointed out that this sensitivity was noticeably affected by exercise intensity followed by work duration 57 ) .…”