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Revisiting classical experiments on the impact of air resistance on metabolic rate, we aimed to overcome limitations of previous research, notably: low participant numbers (n = 1–3), highly turbulent wind, and confounding effects of rising body temperature. In a custom-built wind tunnel with reduced turbulence, 14 participants (8 males, 6 females) walked (5 km·h−1) and ran on a treadmill (70%V̇ o 2max) at 0, 2, 4, and 6 m·s−1 headwind or tailwind in a counterbalanced design, with rest breaks between each exposure to avoid rises in body core temperature. Oxygen consumption (V̇ o 2) exhibited strong linear relationships versus wind direction, dynamic pressure, and air speed squared (Vwr2), lower in magnitude for headwind than tailwind. A moderate linear relationship was observed between heart rate, wind direction, dynamic pressure, and Vwr2. Below 4 m·s−1, the effect of wind was well within inter- and intraindividual variation and equipment uncertainty, and only at wind speeds ≥4 m·s−1 did the differences in physiological responses reach statistical significance. Our data indicate that at running speeds below 4 m·s−1 (14.4 km/h), indoor treadmills and outdoor running are comparable in terms of the metabolic impact of air movement relative to the person. However, this does not extend to the thermoregulatory effect of wind, with outdoor running providing a higher cooling rate due to the self-generated wind created during running. By removing the confounding impact of core temperature rises, the observed effects of headwind were lower and those of tailwind larger than observed previously. In the context of middle-distance running, the headwind created by running at 21.5 km·h−1 would result in a 2.2% increase of V̇ o 2. A relative tailwind of the same speed would lead to a 3.1% reduction. NEW & NOTEWORTHY: Revisiting classical work by Pugh and Davies on the metabolic effects of air speed and direction, shortcomings in the original studies were addressed. Using more participants, less turbulent wind, and avoiding confounding effects of work-induced core temperature increases, new equations describing the impact of air speed/direction were developed. This study observed a lower impact of headwind and a larger impact of tailwind in the absence of an exercise-induced core temperature increase. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate which climate/heat indices perform best in predicting heat-induced loss of physical work capacity (PWCloss). Integrating data from earlier studies, data from 982 exposures (75 conditions) exercising at a fixed cardiovascular load of 130 beats·min−1, in varying temperatures (15–50°C), humidities (20–80%), solar radiation (0–800 W·m−2), wind (0.2–3.5 m·s−1), and two clothing levels, were used to model the predictive power of ambient temperature, universal thermal climate index (UTCI), wet bulb globe temperature (WBGT), modified physiologically equivalent temperature (mPET), heat index, apparent temperature (AT), and wet bulb temperature (Twb) for the calculation of PWCloss, skin temperature (Tskin) and core-to-skin temperature gradient, and thermal perception (thermal sensation vote, TSV) in the heat. R2, RMSE, and Akaike information criterion were used indicating model performance. Indices not including wind/radiation in their calculation (Ta, heat index, AT, and Twb) struggled to provide consistent predictions across variables. For PWCloss and TSV, UTCI and WBGT had the highest predictive power. For Tskin, and core-to-skin temperature gradient, the physiological models UTCI and mPET worked best in seminude conditions, but clothed, AT, WBGT, and UTCI worked best. For all index predictions, Ta, vapor pressure, and Twb were shown to be the worst heat strain predictors. Although UTCI and WBGT had similar model performance using the full dataset, WBGT did not work appropriately in windy, hot-dry, conditions where WBGT predicted lower strain due to wind, whereas the empirical data, UTCI and mPET indicated that wind in fact increased the overall level of thermal strain. The findings of the current study highlight the advantages of using a physiological model-based index like UTCI when evaluating heat stress in dynamic thermal environments. NEW & NOTEWORTHY: There is an urgent need to determine the optimal heat stress metric when forecasting the impact of heat stress on human performance, physiological stress, and perception. We analyzed a wealth of laboratory data, simulating heart rate (HR)-paced work with wide variations in air temperature, humidity, wind speed, solar radiation, and clothing. We conclude that the universal thermal climate index (UTCI) [followed by wet-bulb globe temperature (WBGT)] is the optimal heat index to reliably predict reductions in performance, and elevations in physiological and perceptual stress. [ABSTRACT FROM AUTHOR]

Manual outdoor work is essential in many agricultural systems. Climate change will make such work more stressful in many regions due to heat exposure. The physical work capacity metric (PWC) is a physiologically based approach that estimates an individual's work capacity relative to an environment without any heat stress. We computed PWC under recent past and potential future climate conditions. Daily values were computed from five earth system models for three emission scenarios (SSP1‐2.6, SSP3‐7.0, and SSP5‐8.5) and three time periods: 1991–2010 (recent past), 2041–2060 (mid‐century) and 2081–2100 (end‐century). Average daily PWC values were aggregated for the entire year, the growing season, and the warmest 90‐day period of the year. Under recent past climate conditions, the growing season PWC was below 0.86 (86% of full work capacity) on half the current global cropland. With end‐century/SSP5‐8.5 thermal conditions this value was reduced to 0.7, with most affected crop‐growing regions in Southeast and South Asia, West and Central Africa, and northern South America. Average growing season PWC could falls below 0.4 in some important food production regions such as the Indo‐Gangetic plains in Pakistan and India. End‐century PWC reductions were substantially greater than mid‐century reductions. This paper assesses two potential adaptions—reducing direct solar radiation impacts with shade or working at night and reducing the need for hard physical labor with increased mechanization. Removing the effect of direct solar radiation impacts improved PWC values by 0.05 to 0.10 in the hottest periods and regions. Adding mechanization to increase horsepower (HP) per hectare to levels similar to those in some higher income countries would require a 22% increase in global HP availability with Sub‐Saharan Africa needing the most. There may be scope for shifting to less labor‐intensive crops or those with labor peaks in cooler periods or shift work to early morning. [ABSTRACT FROM AUTHOR]

The lack of sensorial input in the e-commerce domain impairs consumers' online apparel purchases. Therefore, it is important to identify possible compensatory cues to present the 'feel' of a garment in an enhanced way. This study investigates how visual interpretation of the feel of fabrics is related to the actual feel. Haptic textile attributes of seven fabric swatches were quantified in an online questionnaire (part I), simulating an online shopping experience. Separately, a physical assessment of samples mailed to participants (part II), simulating an in-person shopping experience, was performed. Part I and II comprised 20 participants each. No robust significant difference was found between sex. The comparison of the visual only and the visual-haptic assessment showed higher variability and lower scores of the haptic attributes in the visual only session. Especially textile surface structure related haptic attributes could not be conveyed visually and needed tactile sensory input to assess. [ABSTRACT FROM AUTHOR]

Humans are unique among mammals in having a functionally naked body with a hair-covered scalp. Scalp hair is exceptionally variable across populations within Homo sapiens. Neither the function of human scalp hair nor the consequences of variation in its morphology have been studied within an evolutionary framework. A thermoregulatory role for human scalp hair has been previously suggested. Here, we present experimental evidence on the potential evolutionary function of human scalp hair and variation in its morphology. Using a thermal manikin and human hair wigs at different wind speeds in a temperature and humidity-controlled environment, with and without simulated solar radiation, we collected data on the convective, radiative, and evaporative heat fluxes to and from the scalp in relation to properties of a range of hair morphologies, as well as a naked scalp. We find evidence for a significant reduction in solar radiation influx to the scalp in the presence of hair. Maximal evaporative heat loss potential from the scalp is reduced by the presence of hair, but the amount of sweat required on the scalp to balance the incoming solar heat (i.e., zero heat gain) is reduced in the presence of hair. Particularly, we find that hair that is more tightly curled offers increased protection against heat gain from solar radiation. [ABSTRACT FROM AUTHOR]

Purpose: Cycling time-trial performance can be compromised by moderate to high ambient temperatures. It has become commonplace to implement precooling prior to competition to alleviate this performance decline. However, little is known about the ambient temperature threshold above which precooling becomes an effective strategy for enhancing endurance performance. The aim of this study was to investigate the effect of precooling in different environmental temperatures on time-trial (TT) performance. Methods: Trained cyclists completed 2 TTs with (COLD) and without (CON) precooling using an ensemble of ice vest and sleeves in ambient temperatures of 24°C, 27°C, and 35°C. Results: TT performance was faster following COLD in both 35°C (6.2%) and 27°C (2.6%; both Ps <.05) but not 24°C (1.2%). Magnitude-based inferential statistics indicate that COLD was very likely beneficial to performance in 35°C, likely beneficial in 27°C, and possibly beneficial in 24°C. Mean power was 2.4%, 2.5%, and 5.6% higher following COLD and considered to be likely beneficial in 24°C and very likely beneficial in 27°C and 35°C. COLD reduced mean skin temperature throughout the warm-up and into the TT in all ambient temperatures (P <.05). Sweat loss was lower following COLD in 24°C and 27°C but not 35°C. There was no effect of COLD on gastrointestinal temperature at any point. Conclusions: Precooling with an ice vest and sleeves is likely to have a positive effect on TT performance at temperatures above 24°C, with a clear relationship between ambient temperature and the magnitude of effect of precooling. [ABSTRACT FROM AUTHOR]

During the last century about 100 indices were developed to assess influences of the atmosphere on human being. However, most of them have not close relationships with physiological reactions in man. In 1999 International Society of Biometeorology established special study group do develop new Universal Thermal Climate Index (UTCI). Since 2005 these efforts have been reinforced by the COST Action 730 (Cooperation in Science and Technical Development). In February 2009 the Action was terminated and UTCI was developed.