Thermal comfort modelling of body temperature and psychological variations of a human exercising in an outdoor environment

A thermoregulation model based on the physical and physiological characteristics of Chinese elderly

Given the increasing aging population and rising living standards in China, developing an accurate and straightforward thermoregulation model for the elderly has become increasingly essential. To address this need, an existing one-segment four-node thermoregulation model for the young was selected as the base model. This study developed the base model considering age-related physical and physiological changes to predict mean skin temperatures of the elderly. Measured data for model optimization were collected from 24 representative healthy Chinese elderly individuals (average age: 67 years). The subjects underwent temperature step changes between neutral and warm conditions with a temperature range of 25-34 °C. The model's demographic representation was first validated by comparing the subjects' physical characteristics with Chinese census data. Secondly, sensitivity analysis was performed to investigate the influences of passive system parameters on skin and core temperatures, and adjustments were implemented using measurement or literature data specific to the Chinese elderly. Thirdly, the active system was modified by resetting the body temperature set points. The active parameters to control thermoregulation activities were further optimized using the TPE (Tree-structured Parzen Estimator) hyperparameter tuning method. The model's accuracy was further verified using independent experimental data for a temperature range of 18-34 °C for Chinese elderly. By comprehensively considering age-induced thermal response changes, the proposed model has potential applications in designing and optimizing thermal management systems in buildings, as well as informing energy-efficient strategies tailored to the specific needs of the Chinese elderly population.

The effects of warm weather on children's outdoor heat stress and physical activity in a preschool yard in Gothenburg, Sweden

Hot weather conditions can have negative impacts on the thermal comfort and physical activity of vulnerable groups such as children. The aim of this study is to analyze the effects of warm weather on 5-year-old children's thermal comfort and physical activity in a preschool yard in Gothenburg, Sweden. In situ measurements were conducted for 1-1.5 h in the early afternoon on 8 days in May, June, and August of 2022. The thermal comfort and physical activity was estimated with GPS-tracks, heart rate monitors, and step counts and compared to observed weather conditions. Results show that physical activity decreases under warmer weather conditions, depicted by a decrease in distance moved, step counts, and highest registered pulse. Moreover, on warm days, the children avoid sunlit areas. For 50% or more of the time spent in sunlit areas, the children are exposed to cautious levels of heat. In shaded areas, on the other hand, the children are less exposed, with five out of 8 days having 50% or more of the time at neutral levels. The study demonstrates the importance of access to shaded areas in preschool yards where children can continue their active play while simultaneously maintaining a safe thermal status.

Immersive Experience and Climate Change Monitoring in Digital Landscapes: Evidence from Somatosensory Sense and Comfort

In this study, the virtual engine software (Unity 2019, Unity Software Inc., San Francisco, California, the U.S.) was used to generate a digital landscape model, forming a virtual immersive environment. Through field investigation and emotional preference experiments, the ancient tree ecological area and the sunlight-exposed area were respectively monitored, and the somatosensory comfort evaluation model was established. The subjects showed the highest degree of interest in the ancient tree ecological area after landscape roaming experience, and the mean variance in SC fluctuation was 13.23% in experiments. The subjects were in a low arousal state and had a significant degree of interest in the digital landscape roaming scene, and there was a significant correlation between positive emotion, somatosensory comfort and the Rating of Perceived Exertion index; moreover, the somatosensory comfort of the ancient tree ecological area was higher than that of the sunlight-exposed area. Meanwhile, it was found that somatosensory comfort level can effectively distinguish the comfort level between the ancient tree ecological area and the sunlight-exposed area, which provides an important basis for monitoring extreme heat. This study concludes that, in terms of the goal of harmonious coexistence between human and nature, the evaluation model of somatosensory comfort can contribute to reducing people's adverse views on extreme weather conditions.

Analysis of the spatiotemporal mechanism of high temperature on residents’ irritability in Beijing based on multiscale geographically weighted regression model

The emotional health of urban residents is increasingly threatened by high temperatures due to global heating. However, how high temperature affects residents’ emotional health remains unknown. Therefore, this study investigated the spatiotemporal pattern of temperature’s impact on residents’ irritability using data from summer high-temperature measurement and emotional health survey in Beijing, combined with remote sensing images and statistical yearbooks. In detail, this study formulated a multiscale geographically weighted regression (MGWR) model, to study the differentiated and spatial influence of high-temperature factors on emotion. Results show: From 09:00 to 20:00, irritability level rose first then gradually dropped, with a pattern of “aggregation-fragmentation-aggregation.” Irritability is very sensitive to intercept and building density (BD). Other variables all have spatial heterogeneity [except for fraction vegetation coverage (FVC) or road network density (RND) as they are global variables], including normalized difference vegetation index (NDVI), water surface rate (WSR), floor area ratio (FAR), and Modified Normalized Difference Water Index (MNDWI) (sorted from the smallest to the largest in scale). Irritability is negatively correlated with NDVI, WSR, and RND, while positively correlated with intercept, MNDWI, FVC, FAR, and BD. Influence on irritability: WSR < NDVI < BD < MNDWI < RND < intercept < FVC < FAR.

The role of outdoor microclimatic features at long-term care facilities in advancing the health of its residents: An integrative review and future strategies

Projections show that Earth's climate will continue to warm concurrent with increases in the percentage of the world's elderly population. With an understanding that the body's resilience to the heat degrades as it ages, these coupled phenomena point to serious concerns of heat-related mortality in growing elderly populations. As many of the people in this age cohort choose to live in managed long-term care facilities, it's imperative that outdoor spaces of these communities be made thermally comfortable so that connections with nature and the promotion of non-sedentary activities are maintained. Studies have shown that simply being outside has a positive impact on a broad range of the psychosocial well-being of older adults. However, these spaces must be designed to afford accessibility, safety, and aesthetically pleasing experiences so that they are taken full advantage of. Here, we employ an integrative review to link ideas from the disciplines of climate science, health and physiology, and landscape architecture to explain the connections between heat, increased morbidity and mortality in aging adults, existing gaps in thermal comfort models, and key strategies in the development of useable, comfortable outdoor spaces for older adults. Integrative reviews allow for new frameworks or perspectives on a subject to be introduced. Uncovering the synergy of these three knowledge bases can contribute to guiding microclimatic research, design practitioners, and care providers as they seek safe, comfortable and inviting outdoor spaces for aging adults.

Prevalence and Correlates of Observed Sun Protection Behaviors Across Different Public Outdoor Settings in Melbourne, Australia

Skin cancer prevention efforts in Australia have increasingly incorporated a focus on protection during incidental sun exposure. This complements the long-present messages promoting protection in high-risk settings and avoidance of acute intense bouts of sun exposure. Data from two waves of a cross-sectional direct observational survey was used to assess the prevalence and correlates of N = 12,083 adolescents' and adults' sun protection behavior (arm and leg cover, hat, sunglasses, and shade cover). Individuals were observed in public outdoor settings in Melbourne, Australia during peak ultraviolet (UV) times (11 a.m.-3 p.m.) on summer weekends. Settings included pools and beaches, parks and gardens, and for the first time in 2018, outdoor streets and cafés which may capture more incidental forms of sun exposure and represent another public setting where Australians commonly spend time outdoors. Females and older adults were consistently better protected than males and adolescents. Physical activity was strongly associated with low shade cover across settings. Weather was more strongly associated with sun protection at outdoor streets/cafes and parks/gardens than at pools/beaches but use of observed sun protection (particularly arm cover and covering hat) was low across settings. Continued public education about UV risk and its relation to weather and the seasons is needed to promote the routine use of multiple forms of sun protection during outdoor activities in peak UV times, especially among males and adolescents. Findings also highlight the importance of considering activity demands of public spaces in shade planning to optimize sun protection during outdoor activities in public spaces.

Improved methods for estimating mean radiant temperature in hot and sunny outdoor settings

Thermal comfort research has utilized various sensors and models to estimate the mean radiant temperature (MRT) experienced by a human, including the standard black globe thermometer (SGT), acrylic globe thermometers (AGT), and cylindrical radiation thermometers (CRT). Rather than directly measuring radiation, a temperature is measured in the center of these low-cost sensors that can be related to MRT after theoretically accounting for convection. However, these sensors have not been systematically tested under long-term hot and clear conditions. Further, under variable weather conditions, many issues can arise due to slow response times, shape, inaccuracies in material properties and assumptions, and color (albedo, emissivity) inconsistencies. Here, we assess the performance of MRT produced by various heat transfer models, with and without new average surface temperature ([Formula: see text]) correction factors, using five instruments-the SGT (15 cm, black), tan and black CRTs, gray and black 38 mm AGTs-compared to 3D integral radiation measurements. Measurements were taken on an unobscured roof throughout summer-to-early-fall months in Tempe, Arizona, examining 58 full-sun days. Deviations without correcting for asymmetrical surface heating-found to be the main cause of errors-reached ± 15-20 °C MRT. By accounting for asymmetric heating through [Formula: see text] calculations, new corrective algorithms were derived for the low-cost sensor models. Results show significant improvements in the estimated MRT error for each sensor (i.e., ∆MRT_{model - IRM}) when applying the [Formula: see text] corrections. The tan MRT_CRT improved from 1.9 ± 6.2 to -0.1 ± 4.4 °C, while the gray AGT and SGT showed improvements from -1.6 ± 7.2 to -0.4 ± 6.3 °C and - 6.6 ± 6.4 to - 0.03 ± 5.7 °C, respectively. The new corrections also eliminated dependence on other meteorological factors (zenith, wind speed). From these results, we provide three simple equations for CRT, AGT, and SGT correction for future research use under warm-hot and clear conditions. This study is the most comprehensive empirical assessment of various low-cost instruments with broad applicability in urban climate and biometeorological research.

Thermal Environment of Urban Schoolyards: Current and Future Design with Respect to Children’s Thermal Comfort

Urban outdoor thermal conditions, and its impacts on the health and well-being for the city inhabitants have reached increased attention among biometeorological studies during the last two decades. Children are considered more sensitive and vulnerable to hot ambient conditions compared to adults, and are affected strongly by their thermal environment. One of the urban outdoor environments that children spend almost one third of their school time is the schoolyard. The aims of the present manuscript were to review studies conducted worldwide, in order to present the biophysical characteristics of the typical design of the urban schoolyard. This was done to assess, in terms of bioclimatology, the interactions between the thermal environment and the children’s body, to discuss the adverse effects of thermal environment on children, especially the case of heat stress, and to propose measures that could be applied to improve the thermal environment of schoolyards, focusing on vegetation. Human thermal comfort monitoring tools are mainly developed for adults, thus, further research is needed to adapt them to children. The schemes that are usually followed to design urban schoolyards create conditions that favour the exposure of children to excessive heat, inducing high health risks to them. The literature survey showed that typical urban schoolyard design (i.e., dense surface materials, absence of trees) triggered high surface temperatures (that may exceed 58 °C) and increased absorption of radiative heat load (that may exceed 64 °C in terms of Mean Radiant Temperature) during a clear day with intense solar radiation. Furthermore, vegetation cover has a positive impact on schoolyard’s microclimate, by improving thermal comfort and reducing heat stress perception of children. Design options for urban schoolyards and strategies that can mitigate the adverse effects of heat stress are proposed with focus on vegetation cover that affect positively their thermal environment and improve their aesthetic and functionality.

Summertime physiological and thermal responses among activity levels in campus outdoor spaces in a humid subtropical city

We identified physiological and thermal responses to different activity levels on a campus during summertime in Xi'an, a humid subtropical city in China. Physiological responses and thermal comfort of 54 healthy college students while undertaking different physical activities (light, moderate and vigorous intensities) in six campus open spaces were investigated using meteorological measures, longitudinal questionnaire surveys and physiological parameters. Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) were chosen as the thermal indices, while blood pressure (BP), heart rate (HR) and skin temperature (ST) were selected as physiological evaluation measures. Results demonstrated that: 1) Types and proportions of thermal symptoms were positively related to outdoor spatial characteristics and physical activity levels. The proportion of thermal discomfort increased 33, 50 and 83% as activity intensities increased from light through moderate to vigorous. 2) BP and HR reflected human activity levels. HR clearly represented metabolic trends. 3) ST accurately represented physiological responses among spaces across activity levels. However, mean skin temperature (MST) was poorly related to thermal sensation vote (TSV). 4) As activity intensity ranged from light through moderate to vigorous, neutral UTCI declined by 27.6 °C, 25.6 °C, 22.0 °C, and neutral PET declined by 26.1 °C, 22.1 °C, 11.9 °C. 5) Outdoor spaces shaded by trees or pavilions were more comfortable for outdoor activities than these with low or middle SVF during summer.

Exploring outdoor thermal perception-a revised model

This paper aims at extending earlier models of outdoor thermal perception by fusing new knowledge from recent literature and deriving perspectives for future research and methods from the new model. Previous models focused on physical and physiological aspects. Only recently, the psychological aspects of thermal perception received more attention, such as spatial perception. Furthermore, in recent literature on thermal perception, two time scales have been described: the short-term and the long-term thermal perception. Based on this new literature, we develop a conceptual, more comprehensive model that takes these factors into account as well. It hypothesizes how thermal sensation and psychological processes interact on the two time scales. However, to be able to describe relationships between psychological aspects of thermal perception more precisely, more research is required on the following issues: (1) influence of momentary personal references and preferences (e.g., mood), (2) influence of long-term personal references and preferences (e.g., cultural aspects, habituation), and (3) influence of the perception of the spatial environment on thermal perception. Moreover, the relation between momentary and long-term thermal perception has not been studied yet. We conclude this paper with an outlook on possible methods to study these factors.

Empirical Model of Thermal Comfort for Medium-Sized Cities in Subtropical Climate

The present study sought to elaborate an empirical model of thermal comfort for medium-sized cities in subtropical climate, based on a cross-sectional survey in the city of Santa Maria, state of Rio Grande do Sul, Brazil. The research was based on the collection of meteorological, subjective and individual data collected simultaneously in August 2015, January and July 2016, which were submitted to multiple linear regression for the elaboration of the Bioclimatic Model for Subtropical Medium-Sized Cities (MBCMS). The proposed model was validated through a normality test, obtained by the measure of obliquity and kurtosis of the distribution, heteroscedasticity and covariance, as well as by the comparison between already traditional models in the literature, such as PET, SET and PMV, which were calibrated to the study area, and the results observed for MBCMS. The results presented high multiple R-squared and adjusted R-squared, 0.928 and 0.925, respectively, for the proposed model, as well as an F-statistic of 447.6. In the validation, the MBCMS presented R equal to 0.83 and an accuracy score 60% more efficient than the PET, SET and PMV indexes.

Planning for spectator thermal comfort and health in the face of extreme heat: The Tokyo 2020 Olympic marathons

The 2020 Olympic Games marathon will be run through the streets of Tokyo on the mornings of August 2nd and 9th, a time of year that is typically hot, sunny, and humid. Few studies have assessed the potential impact of extreme heat along the marathon course to understand the multiple factors (e.g., radiation, wind flow) affecting human thermal comfort (TC) as influenced by urban design and vegetation. The current research establishes a baseline of microclimate conditions and scenarios to estimate the projected TC along the marathon route for spectators. Mobile microclimate data (air and surface temperatures, solar radiation, humidity, wind speed) were collected along the marathon course over 15 periods in the summer of 2016 and aligned with sky view factors (SVF). Human energy budget modeling was applied to provide spatially-explicit heat budget and TC information along the route. Conditions are expected to create the most discomfort along open, sun-exposed locations, with ~50% of the area along the second half of the course resulting in 'Hot' (budget > 200 W m^-2) or 'Very hot' (budget > 295 W m^-2) conditions. The heat strain index frequently rises above 80% in these locations, with high humidity and low wind flow exacerbating discomfort. Buildings and trees producing a low SVF over roads and sidewalks protect spectators from the morning radiant heat, but such locations should be balanced with wind flow to optimize comfort. The modeling and spatial information can aid in preparing for and mitigating heat stress during the Olympics. Potential solutions can be implemented in collaboration with local organizers and government. This 'research through design' strategy can aid in preparing for and mitigating heat illness during the Olympics. Knowledge gained can be extended to other areas of Tokyo to reduce urban heat, and further provide targeted guidance for effective environmental cooling techniques for human health.

Differences of hemorrhagic and ischemic strokes in age spectra and responses to climatic thermal conditions

The risks of emergency room (ER) visits for cerebral infarction (CI) and intracerebral hemorrhage (ICH) is found to differ in different age groups under different climatic thermal environments. Based on CI and ICH related ER-visit records from three major hospitals in Beijing, China, from 2008 to 2012, the advanced Universal Thermal Climate Index (UTCI), was adopted in this study to assess the climatic thermal environment. Particularly, daily mean UTCI was used as a predictor for the risk of ER visits for CI and ICH. A generalized quasi-Poisson additive model combined with a distributed lag non-linear model was performed to quantify their association. The results indicated that (i) the highest growth rate of ER visits for ICH occurred in age 38 to 48, whereas an increasing ER admissions for CI maintained at age 38 to 78. (ii) The frequency distribution of UTCI in Beijing peaked at -8 and 30 °C, corresponding to moderate cold stress and moderate heat stress, respectively. (iii) Correlation analysis indicated that ICH morbidity was negatively correlated with UTCI, whereas occurrence of CI showed no significant association with UTCI. (iv) The estimated relative risk of ER visits corresponding to 1 °C change in UTCI, which was then stratified by age and gender, indicated that all sub-groups of ICH patients responded similarly to thermal stress. Namely, there is an immediate ICH risk (UTCI = -13 °C, RR = 1.35, 95% CIs: 1.11-1.63) from cold stress on the onset day, but non-significant impact from heat stress. As for CI occurrences, no effect from cold stress was identified, except for only those aged 45 to 65 were threatened by heat stress (UTCI = 38 °C, RR = 1.64, 95% CIs: 1.10-2.44) on lag 0-2 d.

Skin wettedness is an important contributor to thermal behavior during exercise and recovery

We tested the hypothesis that mean skin wettedness contributes to thermal behavior to a greater extent than core and mean skin temperatures. In a 27.0 ± 1.0°C environment, 16 young participants (8 females) cycled for 30 min at 281 ± 51 W·m2, followed by 120 min of seated recovery. Mean skin and core temperatures and mean skin wettedness were recorded continuously. Participants maintained a thermally comfortable neck temperature throughout the protocol using a custom-made device. Neck device temperature provided an index of thermal behavior. Linear regression was performed using individual minute data with mean skin wettedness and core and mean skin temperatures as independent variables and neck device temperature as the dependent variable. Standarized β-coefficients were used to determine relative contributions to thermal behavior. Mean skin temperature differed from preexercise (32.6 ± 0.5°C) to 10 min into exercise (32.3 ± 0.6°C, P < 0.01). Core temperature increased from 37.1 ± 0.3°C preexercise to 37.7 ± 0.4°C by end exercise ( P < 0.01) and remained elevated through 30 min of recovery (37.2 ± 0.3°C, P < 0.01). Mean skin wettedness increased from preexercise [0.14 ± 0.03 arbitrary units (AU)] to 20 min into exercise (0.43 ± 0.09 AU, P < 0.01) and remained elevated through 80 min of recovery (0.18 ± 0.06 AU, P ≤ 0.05). Neck device temperature decreased from 26.4 ± 1.6°C preexercise to 18.5 ± 8.7°C 10 min into exercise ( P = 0.03) and remained depressed through 20 min of recovery (14.4 ± 11.2°C, P < 0.01). Mean skin wettedness (52 ± 24%) provided a greater contribution to thermal behavior compared with core (22 ± 22%, P = 0.06) and mean skin (26 ± 16%, P = 0.04) temperatures. Skin wettedness is an important contributing factor to thermal behavior during exercise and recovery.

Simulation of schoolyard's microclimate and human thermal comfort under Mediterranean climate conditions: effects of trees and green structures

The present study explores the effects on microclimate parameters and on heat stress conditions of the bioclimatic redevelopment of an urban schoolyard based mainly on inserting shading canopies and replacing hard surfaces with green cover. This included the use of the recent version of the microclimate model ENVI-met (V4), first validated using experimental data and then later applied to different case studies in schoolgrounds of Volos, a coastal city in central Greece under Mediterranean type climate. The simulation of the existing yard condition showed that the values of the biometorological index PET (physiologically equivalent temperature, in °C), were within the range of the thermal sensation class of extreme heat stress (> 41 °C) from early morning, while at midday 80.5% of the yard area was within the range of the above class. With the implementation of the redesign proposal, 69.9% of the yard area was improved by two or three PET scale classes, helping to improve the microclimate in 82% of the total area of the courtyard. Tree canopies reduced the direct incident radiation more than 90%, reduced T_mrt and PET index up to 31 °C and 19 °C, respectively, and the surface ground temperatures of wet grass and hard surfaces more than 20 °C and 14 °C, respectively.

Outdoor Thermal Comfort during Anomalous Heat at the 2015 Pan American Games in Toronto, Canada

Mass sporting events in the summertime are influenced by underlying weather patterns, with high temperatures posing a risk for spectators and athletes alike. To better understand weather variations in the Greater Toronto Area (GTA) during the Pan American Games in 2015 (PA15 Games), Environment and Climate Change Canada deployed a mesoscale monitoring network system of 53 weather stations. Spatial maps across the GTA demonstrate large variations by heat metric (e.g., maximum temperature, humidex, and wet bulb globe temperature), identifying Hamilton, Ontario as an area of elevated heat and humidity, and hence risk for heat-related illness. A case study of the Hamilton Soccer Center examined on-site thermal comfort during a heat event and PA15 Soccer Games, demonstrating that athletes and spectators were faced with thermal discomfort and a heightened risk of heat-related illness. Results are corroborated by First Aid and emergency response data during the events, as well as insight from personal experiences and Twitter feed. Integrating these results provides new information on potential benefits to society from utilizing mesonet systems during large-scale sporting events. Results further improve our understanding of intra-urban heat variability and heat-health burden. The benefits of utilizing more comprehensive modeling approaches for human heat stress that coincide with fine-scale weather information are discussed.

Development of a Distributed Modeling Framework to Estimate Thermal Comfort along 2020 Tokyo Olympic Marathon Course

Heat stress is an issue for marathon races in the summer, such as the one planned for the 2020 Tokyo Summer Olympic games. The Tokyo Metropolitan Government is planning to grow existing street trees’ canopies to enlarge their shade to reduce air temperature and solar radiation. To formulate a baseline to assess the effect of street trees and buildings on human thermal comfort, Distributed-COMfort FormulA (D-COMFA), a prototype of a distributed computer model using a geographic information system (GIS) was developed. D-COMFA calculates the energy budget of a human body on a 1 m cell basis, using readily available datasets such as weather measurements and polygon data for street structures. D-COMFA was applied to a street segment along the marathon course in Tokyo on an hourly-basis on 9 August 2016, the hottest day in Tokyo in 2016. Our case study showed that the energy budget was positively related to the sky view factor, air temperature, and solar radiation. The energy budget was reduced on average by 26–62% in the shade throughout the day.

Evaluating the impact of solar radiation on pediatric heat balance within enclosed, hot vehicles

Pediatric deaths due to children being left in hot cars remain a significant yet preventable public health concern. The current study aims to demonstrate the influence of vehicle type, time of day, and solar exposure (sun or shade) on the energy balance and core temperature (T_c) of a hypothetical two-year old boy left in a vehicle on a hot day. Cabin temperatures and relative humidity were collected within six enclosed vehicles under sun or full shade in Tempe, Arizona. These variables and radiation estimates were used to estimate the human energy balance and final T_c across 76 measurement cycles lasting approximately 60minutes. Interior temperatures averaged 39.5°C and 47.6°C in the shade and sun, respectively, at steady-state. Based on the specific heat of a human body, the average T_c after 60 minutes in shaded or sun-exposed vehicles was estimated to reach 38.2±0.29°C and 39.1±0.41°C, respectively, with a significantly higher final T_c in sun-exposed vehicles across all days and in the shaded minivan. Extrapolation to 2 hours is estimated to result in heat injury in the sun. Results demonstrate the influence of radiation on a child's thermal balance in a hot and dry environment. In real-world situations, it is critical to acknowledge variability between children, the starting car environment, and climate (e.g., humid versus dry), and that a child left in any vehicle car can experience potentially lethal core temperatures if forgotten, as shown by vehicular heat stroke statistics. Findings may improve public messaging and reinforce the need for policy action and technological adoption to prevent injury and death.

Skin Temperature Measurement Using Contact Thermometry: A Systematic Review of Setup Variables and Their Effects on Measured Values

Background: Skin temperature (T_skin) is commonly measured using T_skin sensors affixed directly to the skin surface, although the influence of setup variables on the measured outcome requires clarification. Objectives: The two distinct objectives of this systematic review were (1) to examine measurements from contact T_skin sensors considering equilibrium temperature and temperature disturbance, sensor attachments, pressure, environmental temperature, and sensor type, and (2) to characterise the contact T_skin sensors used, conditions of use, and subsequent reporting in studies investigating sports, exercise, and other physical activity. Data sources and study selection: For the measurement comparison objective, Ovid Medline and Scopus were used (1960 to July 2016) and studies comparing contact T_skin sensor measurements in vivo or using appropriate physical models were included. For the survey of use, Ovid Medline was used (2011 to July 2016) and studies using contact temperature sensors for the measurement of human T_skinin vivo during sport, exercise, and other physical activity were included. Study appraisal and synthesis methods: For measurement comparisons, assessments of risk of bias were made according to an adapted version of the Cochrane Collaboration's risk of bias tool. Comparisons of temperature measurements were expressed, where possible, as mean difference and 95% limits of agreement (LoA). Meta-analyses were not performed due to the lack of a common reference condition. For the survey of use, extracted information was summarised in text and tabular form. Results: For measurement comparisons, 21 studies were included. Results from these studies indicated minor (<0.5°C) to practically meaningful (>0.5°C) measurement bias within the subgroups of attachment type, applied pressure, environmental conditions, and sensor type. The 95% LoA were often within 1.0°C for in vivo studies and 0.5°C for physical models. For the survey of use, 172 studies were included. Details about T_skin sensor setup were often poorly reported and, from those reporting setup information, it was evident that setups widely varied in terms of type of sensors, attachments, and locations used. Conclusions: Setup variables and conditions of use can influence the measured temperature from contact T_skin sensors and thus key setup variables need to be appropriately considered and consistently reported.

Skin Temperature Measurement Using Contact Thermometry: A Systematic Review of Setup Variables and Their Effects on Measured Values

Background: Skin temperature (Tskin) is commonly measured using Tskin sensors affixed directly to the skin surface, although the influence of setup variables on the measured outcome requires clarification. Objectives: The two distinct objectives of this systematic review were (1) to examine measurements from contact Tskin sensors considering equilibrium temperature and temperature disturbance, sensor attachments, pressure, environmental temperature, and sensor type, and (2) to characterise the contact Tskin sensors used, conditions of use, and subsequent reporting in studies investigating sports, exercise, and other physical activity. Data sources and study selection: For the measurement comparison objective, Ovid Medline and Scopus were used (1960 to July 2016) and studies comparing contact Tskin sensor measurements in vivo or using appropriate physical models were included. For the survey of use, Ovid Medline was used (2011 to July 2016) and studies using contact temperature sensors for the measurement of human Tskinin vivo during sport, exercise, and other physical activity were included. Study appraisal and synthesis methods: For measurement comparisons, assessments of risk of bias were made according to an adapted version of the Cochrane Collaboration's risk of bias tool. Comparisons of temperature measurements were expressed, where possible, as mean difference and 95% limits of agreement (LoA). Meta-analyses were not performed due to the lack of a common reference condition. For the survey of use, extracted information was summarised in text and tabular form. Results: For measurement comparisons, 21 studies were included. Results from these studies indicated minor (<0.5°C) to practically meaningful (>0.5°C) measurement bias within the subgroups of attachment type, applied pressure, environmental conditions, and sensor type. The 95% LoA were often within 1.0°C for in vivo studies and 0.5°C for physical models. For the survey of use, 172 studies were included. Details about Tskin sensor setup were often poorly reported and, from those reporting setup information, it was evident that setups widely varied in terms of type of sensors, attachments, and locations used. Conclusions: Setup variables and conditions of use can influence the measured temperature from contact Tskin sensors and thus key setup variables need to be appropriately considered and consistently reported.

The influence of surface type on the absorbed radiation by a human under hot, dry conditions

Given the predominant use of heat-retaining materials in urban areas, numerous studies have addressed the urban heat island mitigation potential of various "cool" options, such as vegetation and high-albedo surfaces. The influence of altered radiational properties of such surfaces affects not only the air temperature within a microclimate, but more importantly the interactions of long- and short-wave radiation fluxes with the human body. Minimal studies have assessed how cool surfaces affect thermal comfort via changes in absorbed radiation by a human (R _abs) using real-world, rather than modeled, urban field data. The purpose of the current study is to assess the changes in the absorbed radiation by a human-a critical component of human energy budget models-based on surface type on hot summer days (air temperatures > 38.5^∘C). Field tests were conducted using a high-end microclimate station under predominantly clear sky conditions over ten surfaces with higher sky view factors in Lubbock, Texas. Three methods were used to measure and estimate R _abs: a cylindrical radiation thermometer (CRT), a net radiometer, and a theoretical estimation model. Results over dry surfaces suggest that the use of high-albedo surfaces to reduce overall urban heat gain may not improve acute human thermal comfort in clear conditions due to increased reflected radiation. Further, the use of low-cost instrumentation, such as the CRT, shows potential in quantifying radiative heat loads within urban areas at temporal scales of 5-10 min or greater, yet further research is needed. Fine-scale radiative information in urban areas can aid in the decision-making process for urban heat mitigation using non-vegetated urban surfaces, with surface type choice is dependent on the need for short-term thermal comfort, or reducing cumulative heat gain to the urban fabric.

Heat: a primer for public health researchers

OBJECTIVES

To provide a primer on the physical characteristics of heat from a biometeorological perspective for those interested in the epidemiology of extreme heat.

STUDY DESIGN

A literature search design was used.

METHODS

A review of the concepts of heat, heat stress and human heat balance was conducted using Web of Sciences, Scopus and PubMed.

RESULTS

Heat, as recognised in the field of human biometeorology, is a complex phenomenon resulting from the synergistic effects of air temperature, humidity and ventilation levels, radiation loads and metabolic activity. Heat should therefore not be conflated with high temperatures. A range of empirical, direct and rational heat stress indices have been developed to assess heat stress.

CONCLUSION

The conceptualisation of heat stress is best described with reference to the human heat balance which describes the various avenues for heat gain to and heat loss from the body. Air temperature alone is seldom the reason for heat stress and thus heat-related health effects.

Associations between Thermal and Physiological Responses of Human Body during Exercise

In this study, thermal behaviours of the athletes were investigated with respect to thermal comfort and exercise intensity. The relationship between an index for analysing thermal comfort (Predicted Mean Vote: PMV) and Rating of Perceived Exertion (RPE) which shows exercise intensity and exhaustion level was evaluated. Eleven moderately trained male athletes (V˙O_2max 54 ± 9.9 mL∙min⁻¹∙kg⁻¹) had volunteered for the study (age: 22.2 ± 3.7 years; body mass: 73.8 ± 6.9 kg; height: 181 ± 6.3 cm; Body surface area (BSA): 1.93 ± 0.1 m²; body fat: 12.6% ± 4.2%; V˙O_2max: 54 ± 9.9 mL∙min⁻¹∙kg⁻¹). Experiments were carried out by using a cycle ergometer in an air-conditioned test chamber which provided fresh air and had the ability to control the temperature and relative humidity. The study cohort was divided into two groups according to maximal oxygen consumption levels of the participants. Statistical analyses were conducted with the whole study cohort as well as the two separated groups. There was a moderate correlation between PMV and RPE for whole cohort (r: −0.51). When the whole cohort divided as low and high aerobic power groups, an average correlation coefficient at high oxygen consumption cohort decreased to r: −0.21, while the average correlation coefficient at low oxygen consumption cohort increased to r: −0.77. In conclusion, PMV and RPE have a high correlation in less trained participants, but not in the more trained ones. The case may bring to mind that thermal distribution may be better in high aerobic power group in spite of high RPE and thus the relation between PMV and RPE is affected by exercise performance status.

American football and fatal exertional heat stroke: a case study of Korey Stringer

On August 1, 2001, Korey Stringer, a Pro Bowl offensive tackle for the Minnesota Vikings, became the first and to date the only professional American football player to die from exertional heat stroke (EHS). The death helped raise awareness of the dangers of exertional heat illnesses in athletes and prompted the development of heat safety policies at the professional, collegiate, and interscholastic levels. Despite the public awareness of this death, no published study has examined in detail the circumstances surrounding Stringer's fatal EHS. Using the well-documented details of the case, our study shows that Stringer's fatal EHS was the result of a combination of physiological limitations, organizational and treatment failings, and extreme environmental conditions. The COMfort FormulA (COMFA) energy budget model was used to assess the relative importance of several extrinsic factors on Stringer's EHS, including weather conditions, clothing insulation, and activity levels. We found that Stringer's high-intensity training in relation to the oppressive environmental conditions was the most prominent factor in producing dangerous, uncompensable heat stress conditions and that the full football uniform played a smaller role in influencing Stringer's energy budget. The extreme energy budget levels that led to the fatal EHS would have been avoided according to our modeling through a combination of reduced intensity and lower clothing insulation. Finally, a long delay in providing medical treatment made the EHS fatal. These results highlight the importance of modern heat safety guidelines that provide controls on extrinsic factors, such as the adjustment of duration and intensity of training along with protective equipment modifications based on environmental conditions and the presence of an emergency action plan focused on rapid recognition and immediate on-site aggressive cooling of EHS cases.

Modeling the Effects of Urban Design on Emergency Medical Response Calls during Extreme Heat Events in Toronto, Canada

Urban residents are at risk of health-related illness during extreme heat events but the dangers are not equal in all parts of a city. Previous studies have found a relationship between physical characteristics of neighborhoods and the number of emergency medical response (EMR) calls. We used a human energy budget model to test the effects of landscape modifications that are designed to cool the environment on the expected number of EMR calls in two neighborhoods in Toronto, Canada during extreme heat events. The cooling design strategies reduced the energy overload on people by approximately 20–30 W m⁻², resulting in an estimated 40–50% reduction in heat-related ambulance calls. These findings advance current understanding of the relationship between the urban landscape and human health and suggest straightforward design strategies to positively influence urban heat-health.

Heterogeneity in individually experienced temperatures (IETs) within an urban neighborhood: insights from a new approach to measuring heat exposure

Urban environmental health hazards, including exposure to extreme heat, have become increasingly important to understand in light of ongoing climate change and urbanization. In cities, neighborhoods are often considered a homogenous and appropriate unit with which to assess heat risk. This manuscript presents results from a pilot study examining the variability of individually experienced temperatures (IETs) within a single urban neighborhood. In July 2013, 23 research participants were recruited from the South End neighborhood of Boston and equipped with Thermochron iButtons that measured the air temperatures surrounding individuals as they went about their daily lives. IETs were measured during a heat wave period (July 17-20), which included 2 days with excessive heat warnings and 1 day with a heat advisory, as well as a reference period (July 20-23) in which temperatures were below seasonal averages. IETs were not homogeneous during the heat wave period; mean IETs were significantly different between participants (p < 0.001). The majority of participants recorded IETs significantly lower than outdoor ambient temperatures (OATs), and on average, the mean IET was 3.7 °C below the mean OAT. Compared with IETs during the reference period, IETs during the heat wave period were 1.0 °C higher. More than half of participants did not experience statistically different temperatures between the two test periods, despite the fact that the mean OAT was 6.5 °C higher during the heat wave period. The IET data collected for this sample and study period suggest that (1) heterogeneity in individual heat exposure exists within this neighborhood and that (2) outdoor temperatures misrepresent the mean experienced temperatures during a heat wave period. Individual differences in attributes (gender, race, socioeconomic status, etc.), behaviors (schedules, preferences, lifestyle, etc.), and access to resources are overlooked determinants of heat exposure and should be better integrated with group- and neighborhood-level characteristics. Understanding IETs for the population at large may lead to innovative advances in heat-health intervention and mitigation strategies.

Children's health and vulnerability in outdoor microclimates: A comprehensive review

BACKGROUND

Children are routinely identified as a vulnerable population in environmental health risk assessments, experiencing adverse health outcomes due to exposure to a suite of atmospheric constituents.

OBJECTIVE

To provide a substantive overview of the research literature pertaining to biometeorological effects on children. Key information areas within urban environmental health research related to atmospheric variables (heat, air pollution, radiation) are assessed and integrated to better understand health outcomes and vulnerabilities in children. Critical avenues for improvement and understanding of children's health related to such biophysical parameters are also identified.

METHODS

This comprehensive review assesses past and current primary studies, organizational reports, educational books, and review articles. Emphasis is placed on the differential ambient exposures to temperature, air pollution, and radiation within urban microclimates commonly used by children (e.g., schoolyards, urban parks), and the resulting health impacts.

DISCUSSION

Exposure to heat, air pollution, and radiation are often enhanced in urban areas, specifically under the current design of the majority of outdoor child play places. Many heat indices, energy budget models, and health outcome studies fail to adequately parameterize children, yet those that do find enhanced vulnerability to ambient stressors, particularly heat and air pollution. Such environmental exposures relate strongly to behavior, activity, asthma, obesity, and overall child well-being. Current research indicates that a changing climate, growing urban population, and unsustainable design are projected to pose increasing complications.

CONCLUSIONS

Evidence-based research to link children's health, physiology, and behavior to atmospheric extremes is an important future research avenue, underscoring the fact that children are among the population groups disproportionately affected by ambient extremes. However, current methods and population-based models lack child-specific inputs and outputs, as well as designated thresholds for accurate predictions of child health impacts. More substantive evidence is needed for applicable child-specific policies and guidelines.

Improved predictive ability of climate-human-behaviour interactions with modifications to the COMFA outdoor energy budget model

The purpose of this paper is to implement current and novel research techniques in human energy budget estimations to give more accurate and efficient application of models by a variety of users. Using the COMFA model, the conditioning level of an individual is incorporated into overall energy budget predictions, giving more realistic estimations of the metabolism experienced at various fitness levels. Through the use of VO(2) reserve estimates, errors are found when an elite athlete is modelled as an unconditioned or a conditioned individual, giving budgets underpredicted significantly by -173 and -123 W m(-2), respectively. Such underprediction can result in critical errors regarding heat stress, particularly in highly motivated individuals; thus this revision is critical for athletic individuals. A further improvement in the COMFA model involves improved adaptation of clothing insulation (I (cl)), as well clothing non-uniformity, with changing air temperature (T (a)) and metabolic activity (M (act)). Equivalent T (a) values (for I (cl) estimation) are calculated in order to lower the I (cl) value with increasing M (act) at equal T (a). Furthermore, threshold T (a) values are calculated to predict the point at which an individual will change from a uniform I (cl) to a segmented I (cl) (full ensemble to shorts and a T-shirt). Lastly, improved relative velocity (v (r)) estimates were found with a refined equation accounting for the degree angle of wind to body movement. Differences between the original and improved v (r) equations increased with higher wind and activity speeds, and as the wind to body angle moved away from 90°. Under moderate microclimate conditions, and wind from behind a person, the convective heat loss and skin temperature estimates were 47 W m(-2) and 1.7°C higher when using the improved v (r) equation. These model revisions improve the applicability and usability of the COMFA energy budget model for subjects performing physical activity in outdoor environments. Application is possible for other similar energy budget models, and within various urban and rural environments.