Determination of clothing microclimate volume

Human heat transfer depends on the amount of ventilation between the skin and the clothing layers, which in turn depends on the microclimate volume (7). This volume is hard to quantify. The traditional method, developed by Crockford et al. (4) and further in Birnbaum and Crockford (1) and Sullivan et al. (10) utilises a vacuum oversuit to evacuate and measure the quantity of air trapped in the microenvironment. This method is cumbersome and an alternative may be found in a model approach or using 3D whole body scans. Lee and Hong (8) endeavoured to ascertain the relationship between the insulation value of the clothing ensemble and the air volume measured by using phase-shifting moiré topography. They determined the microclimate volume between a manikin and a T-shirt. This technique was time efficient and accurate, but it was not reported if this technique could be used on humans and how the results compared to the traditional technique of microclimate volume measurement. A third technique to estimate the microclimate volume assumes that the body is represented by a series of cylinders. The circumference of each segment is measured with and without clothing, allowing the volume of each to be calculated. The method was adopted from Lotens and Havenith (9) and is fast and simple. It is the purpose of this study to compare the reliability and reproducibility of the vacuum suit method, scanning method and cylinder model to determine microclimate volume

Endothermic salts integrated in impermeable suits do not reduce heat strain during exercise

Wearing impermeable garments during work inherently leads to heat strain, even in cold environments [1]. Phase change materials (mainly paraffin’s or salt [4]) may be used as a thermal buffer (e.g. [2]) to reduce initial heat stress. Salts can also be used to absorb sweat, which may enhance the cooling power from the skin. Recently, specific encapsulated salts utilising KSCN (potassium thiocyanate) have been developed that consume energy when the KSCN dissolves in water. The heat consumed when the KSCN (present inside 150 g of capsules containing 60% KSCN salt) dissolves in water is 22410 J (249 J/g * 60% * 150 g). When this solving takes place over a period of 30 minutes, the average power transfer is 12 W. One (1) g of KSCN-containing capsules absorbs close to 1 g of moisture. If we assume that 150 g sweat extra can be evaporated from the skin, this yields an extra cooling power of 182 W for 30 minutes. However this evaporated water from the skin is subsequently absorbed by the KSCN in the capsules. During this absorption from the gas phase, the condensation heat is released to the KSCN salt: about 182 W for 30 minutes. However, we hypothesise that this condensation heat will be partly transferred to the body and partly to the environment [3], providing a net benefit to the body. Thus, the total cooling effect due to the salt capsules is composed of two parts: • The cooling effect of about 12 W due to the heat consumption by the dissolving of the salts in water; • The cooling effect of maximal 182 W, which equals the difference between the evaporative heat and the condensation heat. The latter is generated in the salt capsules that transfer part of the heat to the environment. The overall cooling effect should therefore be in between 12 W and 194 W. The purpose of our study was to test the efficacy of a KSCN-based absorbing salt as a PCM for use within impermeable protective clothing. We tested the PCM during 20 min of moderate exercise in a hot (35°C, 40% relative humidity) environment, and hypothesized that thermal strain would be lower in the PCM compared to the non-PCM condition

Sex differences in temperature-related all-cause mortality in the Netherlands

Purpose: Over the last few decades, a global increase in both cold and heat extremes has been observed with significant impacts on human mortality. Although it is well-identified that older individuals (> 65 years) are most prone to temperature-related mortality, there is no consensus on the effect of sex. The current study investigated if sex differences in temperature-related mortality exist in the Netherlands. Methods: Twenty-three-year ambient temperature data of the Netherlands were combined with daily mortality data which were subdivided into sex and three age classes (< 65 years, 65–80 years, ≥ 80 years). Distributed lag non-linear models were used to analyze the effect of ambient temperature on mortality and determine sex differences in mortality attributable to the cold and heat, which is defined as mean daily temperatures below and above the Minimum Mortality Temperature, respectively. Results: Attributable fractions in the heat were higher in females, especially in the oldest group under extreme heat (≥ 97.5th percentile), whilst no sex differences were found in the cold. Cold- and heat-related mortality was most prominent in the oldest age group (≥ 80 years) and to a smaller extent in the age group between 65–80 years. In the age group < 65 years temperature-related mortality was only significant for males in the heat. Conclusion: Mortality in the Netherlands represents the typical V- or hockey-stick shaped curve with a higher daily mortality in the cold and heat than at milder temperatures in both males and females, especially in the age group ≥ 80 years. Heat-related mortality was higher in females than in males, especially in the oldest age group (≥ 80 years) under extreme heat, whilst in the cold no sex differences were found. The underlying cause may be of physiological or behavioral nature, but more research is necessary

PHYSIOLOGICAL EFFECTS AFTER EXPOSURE TO HEAT: A BRIEF LITERATURE REVIEW

Many employees are exposed to heat stress during their work. Although the direct effects of heat are well reported, the long term physiological changes after heat exposure are hardly described. The present manuscript addresses these issues in the form of a brief literature review. Repeated heat exposure results in heat acclimatization, these physiological adaptations decay gradually afterwards, re-increasing the vulnerability to heat injuries. Repeated heat exposure may lead to kidney damage (related to dehydration) and reduced efficiency of the reproductive system. A history of heat stroke may increase the sensitivity to heat illness. The increased susceptibility possibly indicates an impaired thermoregulatory system resulting from a heat stroke, or a genetic predisposition prior to the first heat stroke

Validity and Repeatability of the Sizestream 3D Scanner and Poikos Modeling System

Three-dimensional (3D) body scanning becomes increasingly important in the medical, ergonomical and apparel industry. The SizeStream 3D body scanner is a 3D body scanner in the shape of a fitting room that can generate a 3D copy of the human body in a few seconds. The Poikos modeling system generates a 3D image of a person using a front- and side photo. This study evaluates the repeatability and validity of both systems with human subjects. Hundred fifty-six participants were included in this study, of whom 85 were scanned twice by the SizeStream Scanner and 139 by the Poikos modeling system. The repeatability is assessed by calculating the intra-class correlation coefficients (ICC) and standard error of measurement (SEM), and the validity of 6 Sizestream and 4 Poikos measurements is evaluated by comparing these measurements with collected tape measurements. The ICC and the SEM results indicate that 79 of the 163 SizeStream measurements are repeatable enough to use for fashion purposes, since they had an ICC above 0.80 and a SEM below 10mm. Fifty-one measurements give a good indication but are not accurate enough for pattern making. The waist, chest and hip circumferences are valid after a correction of the over- or underestimation of the measurements. The Poikos modeling system is a promising, but is as expected, less repeatable and valid than the SizeStream scanner. Although the Poikos modeling system can give a good estimation of the body shape, the measurements are not accurate enough (SEM > 10mm) to use in the fashion industry. Future studies have to be performed to validate more Poikos and SizeStream measurements and to assess the usability of these measurements for the fashion industry

Heat flux systems for body core temperature assessment during exercise

Heat flux systems are increasingly used to assess core body temperature. However, validation of multiple systems is scarce. Therefore, an experiment was performed in which three commercially available heat flux systems (3 M, Medisim and Core) were compared to rectal temperature (Tre). Five females and four males performed exercise in a climate chamber set at 18 °C/50% relative humidity until exhaustion. Exercise duration was 36.3 ± 5.6 min (mean ± standard deviation). Tre in rest was 37.2 ± 0.3 °C. Medisim's-values were lower than Tre (36.9 ± 0.4 °C, p < 0.05); 3 M (37.2 ± 0.1 °C) and Core's (37.4 ± 0.3 °C) did not differ from Tre. Maximal temperatures after exercise were 38.4 ± 0.2 °C (Tre), 38.0 ± 0.4 °C (3 M), 38.8 ± 0.3 °C (Medisim) and 38.6 ± 0.3 °C (Core); Medisim was significantly higher than Tre (p < 0.05). The temperature profiles of the heat flux systems during exercise differed to varying degree from the rectal profiles; the Medisim system showed a faster increase during exercise than Tre (0.48 ± 0.25 °C in 20 min, p < 0.05), the Core system tended to show a systematic overestimation during the entire exercise period and the 3 M system showed large errors at the end of exercise, likely due to sweat entering the sensor. Therefore, the interpretation of heat flux sensor values as core body temperature estimates should be done with care; more research is required to elucidate the physiological significance of the generated temperature values

3D body scanning

Clothing selection is generally made on the basis of appearance (looks and fashion), costs, and fit. Traditionally, clothing items are fitted in the retail outlet, but increasingly garments are purchased over the internet, making physical fitting impossible. Therefore, the technology of 3D body scanning becomes increasingly important. In the last decades bulky and costly 3D body scanners evolved to inexpensive, accurate, and easy-to-use devices. The 3D scans form a digital copy of the outside of the body and can be interfaced with the clothing patterns, a process called virtual fitting. The actual fit can be visualized using color maps representing the distance between garments and the skin (for loose fit) or visualization of the strain in the textiles (for tight fit). Also, making the clothing transparent on a rigid body can be used for fit assessment. The existing models are unfortunately poorly validated and mainly limited to static body postures, but new developments have started to face these challenges, for instance, standardization initiatives within International Standardization Organization, NATO, and Institute of Electrical and Electronics Engineers