Thermophysiological Responses Research Articles

Optimizing personal comfort: Short-term personalized heating impact on sanitation workers' thermo-physiological responses

The potential of Personal Comfort Systems (PCS) in outdoor applications, particularly their short-term efficacy in cold environments, is pivotal for enhancing thermo-physiological safety among sanitation workers. Our study evaluated four heating modalities—Continuous Heating (CH), Continuous Heating under Windproof Tent (CHW), Intermittent Heating (IH), and Intermittent Heating under Windproof Tent (IHW)—to determine their impact on thermal-physiological responses in winter conditions. We constructed initial temperature response models to refine PCS performance, yielding four key insights: 1) Thermal sensation vote (TSV), Thermal comfort vote (TCV), and Local thermal sensation vote (LTSV) varied across heating modes, with CH and CHW eliciting greater increases than IH and IHW. 2) Chest skin temperature rose consistently during personalized heating, whereas upper arm and lower calf skin temperatures were influenced by the integrated thermal environment. 3) Personalized adjustments led to optimal heating states, with CHW achieving the highest mean final heating temperature at waist, buttocks, and thighs, and CH at the upper back. 4) Machine learning algorithms, particularly Random Forest Regression models, were instrumental in developing predictive models, demonstrating high accuracy (R2 > 0.9) for initial temperature optimization.

Predicting the thermophysiological response in hot environment when using protective clothing

Predicting the thermophysiological response in hot environment when using protective clothing

Impact of a simulated multiday heatwave on nocturnal physiology, behavior, and sleep: a 10-day confinement study.

This study investigated the impact of a multiday heatwave on nocturnal physiology, behavior, and sleep under controlled conditions with comprehensive monitoring of environmental factors and participant activities. Seven young healthy males were confined for 10 days in controlled conditions that ranged between hot-to-warm (day: 35.4°C, night: 26.3°C) during nights 4-6 and temperate (day: 25.4°C, night: 22.3°C) before (nights 1-3) and after (nights 7-10) the heatwave. Measurements included core and skin temperatures, heart rate, sympathovagal balance, vasomotion indicators, urine samples, blanket coverage, subjective sleep assessments, and partial polysomnography. The average nocturnal core temperature was 0.2°C higher during and after the heatwave compared to the pre-heatwave period, with this difference being more pronounced (+0.3°C) in the first 2 h of sleep (p<0.001). For every 0.1°C rise in overnight core temperature, the total sleep time decreased by 14 min (pseudo-R2=0.26, p=0.01). The elevated core temperatures occurred despite the participants exhibiting evident thermoregulatory behavior, as they covered 30% less body surface during the heatwave compared to pre- and post-heatwave periods (p<0.001). During the heatwave, mean skin temperature at bedtime was 1.3°C higher than pre-heatwave and 0.8°C higher than post-heatwave periods (p<0.001). No differences in other responses, including heart rate and vasomotion indicators, were observed. The paper details a 20-min sleepwalking episode that was coupled with marked changes in sleepwalker's thermophysiological responses. In conclusion, the simulated heatwave resulted in higher overnight core temperature which was associated with reduced total sleep time. Behavioral thermoregulation during sleep may serve as a defense against these effects, though more research is needed.

Thermophysiological responses and thermal comfort of occupants in indoor spaces under different speaking and non-speaking conditions

As speaking is one of the fundamental behaviours in human activities, understanding the thermal comfort of occupants during speaking is crucial to providing a satisfactory environment. To further strengthen this understanding and identify how occupant thermal responses change during speaking activities, this study performs an experiment to examine the thermophysiological parameters and thermal comfort of occupants across three different speaking and non-speaking conditions: (1) silent (i.e., non-speaking); (2) speech (i.e., continuous speaking); and (3) conversation (i.e., intermittent speaking). During the experiment, thermophysiological parameters, including skin temperature, electrodermal activity, and heart rate, were collected using smart wristbands from 30 subjects at three different temperature settings to represent three distinct thermal environmental conditions: (1) Cold: 20 °C; (2) Neutral: 24 °C; and (3) Hot: 28 °C. Subjects were also required to report their thermal comfort perceptions in terms of thermal sensation votes, thermal preference votes, and thermal satisfaction votes. Repeated measures ANOVA test and Friedman test were used to analyse the thermophysiological parameters and thermal comfort perceptions. The null hypothesis, which suggests no significant differences in thermal responses and comfort across the three speaking conditions, will be rejected at a significance level of 0.05 (two-tail). The results revealed significant differences in all three thermophysiological parameters between speaking conditions at all temperature settings, while the thermal comfort perception did not consistently show statistically significant differences between speaking conditions. The findings contribute to our understanding of the relationship between communication and thermal responses, highlighting the importance of contextual factors in designing comfortable environments for speaking-related activities.

Proposing a strategy based on body-thermal status to improve the welfare of heat-stressed and water-deprived goats (Capra hircus).

Despite the considerable body of research on the effects of heat stress coupled with water scarcity (either through restriction or deprivation) on goats, aimed at enhancing their welfare, there remains a notable gap in the literature regarding the subsequent period following water restoration, during which the cumulative impact is fully alleviated. In response to this gap, we propose a strategy grounded in the assessment of body-thermal status to improve the welfare of heat-stressed and water-deprived goats. Specifically, our strategy seeks to determine the minimally required recovery interval necessary to completely mitigate the residual effects of water deprivation endured for a duration of 72 hours. Eight healthy Aardi bucks, aged 10 months and weighing 30 kg, were subjected to three distinct stages: euhydration, dehydration, and rehydration. Each stage spanned for 72 hours except for the rehydration stage, which was left unrestricted. Various meteorological, biophysiological, and thermophysiological measurements were subsequently recorded. Exposure of heat-stressed goats, as indicated by the temperature-humidity index values, to a 72 hours deprivation period resulted in noticeable (p<0.05) alterations in their biophysiological (daily feed intake, body weight, and feces water content) and thermophysiological responses (core, rectal, skin, and surface temperatures, respiratory and heart rates, internal, external, and total body-thermal gradients, heat tolerance and adaptability coefficients, heterothermial total body-heat storage, and total water conservation). Remarkably, our findings demonstrate that all assessed variables, whether measured or estimated, returned to their baseline euhydration levels within 10 days of commencing the rehydration phase. In order to improve the welfare of heat-stressed and 72 hours water-deprived goats, it is imperative to allow a recovery period of no less than 10 days following the restoration of water access prior to initiating any subsequent experiments involving these animals. Such experiments, addressing these critical aspects, serve to advance our understanding of goat welfare and obviously hold promise for contributing to future food security and economic viability.

Thermophysiological responses of ginseng to abnormal season-long high temperature

Thermophysiological responses of ginseng to abnormal season-long high temperature

Sex differences in thermophysiological responses of elderly to low-intensity exercise during uncompensable heat strain

PurposeThe rising frequency of extreme heat events poses an escalating threat of heat-related illnesses and fatalities, placing an additional strain on global healthcare systems. Whether the risk of heat-related issues is sex specific, particularly among the elderly, remains uncertain.Methods16 men and 15 women of similar age (69 ± 5 years) were exposed to an air temperature of 39.1 ± 0.3 °C and a relative humidity (RH) of 25.1 ± 1.9%, during 20 min of seated rest and at least 40 min of low-intensity (10 W) cycling exercise. RH was gradually increased by 2% every 5 min starting at minute 30. We measured sweat rate, heart rate, thermal sensation, and the rise in gastrointestinal temperature (Tgi) and skin temperature (Tsk).ResultsTgi consistently increased from minute 30 to 60, with no significant difference between females and males (0.012 ± 0.004 °C/min vs. 0.011 ± 0.005 °C/min; p = 0.64). Similarly, Tsk increase did not differ between females and males (0.044 ± 0.007 °C/min vs. 0.038 ± 0.011 °C/min; p = 0.07). Females exhibited lower sweat rates than males (0.29 ± 0.06 vs. 0.45 ± 0.14 mg/m2/min; p < 0.001) in particular at relative humidities exceeding 30%. No sex differences in heart rate and thermal sensation were observed.ConclusionElderly females exhibit significantly lower sweat rates than their male counterparts during low-intensity exercise at ambient temperatures of 39 °C when humidity exceeds 30%. However, both elderly males and females demonstrate a comparable rise in core temperature, skin temperature, and mean body temperature, indicating similar health-related risks associated with heat exposure.

Projection of future heat-related morbidity in three metropolitan prefectures of Japan based on large ensemble simulations of climate change under 2 °C global warming scenarios

Recently, global warming has become a prominent topic, including its impacts on human health. The number of heat illness cases requiring ambulance transport has been strongly linked to increasing temperature and the frequency of heat waves. Thus, a potential increase in the number of cases in the future is a concern for medical resource management. In this study, we estimated the number of heat illness cases in three prefectures of Japan under 2 °C global warming scenarios, approximately corresponding to the 2040s. Based on the population composition, a regression model was used to estimate the number of heat illness cases with an input parameter of time-dependent meteorological ambient temperature or computed thermophysiological response of test subjects in large-scale computation. We generated 504 weather patterns using 2 °C global warming scenarios. The large-scale computational results show that daily amount of sweating increased twice and the core temperature increased by maximum 0.168 °C, suggesting significant heat strain. According to the regression model, the estimated number of heat illness cases in the 2040s of the three prefectures was 1.90 (95%CI: 1.35–2.38) times higher than that in the 2010s. These computational results suggest the need to manage ambulance services and medical resource allocation, including intervention for public awareness of heat illnesses. This issue will be important in other aging societies in near future.

Thermo-Physiological Responses of Sailors in a Disabled Submarine With Interior Cabin Temperature and Humidity Slowly Rising As Predicted by Computer Simulation Techniques &lt;br&gt;

Thermo-Physiological Responses of Sailors in a Disabled Submarine With Interior Cabin Temperature and Humidity Slowly Rising As Predicted by Computer Simulation Techniques &lt;br&gt;

Comparison of biophysical characteristics and predicted thermophysiological responses of three prototype body armor systems versus baseline U.S. Army body armor systems &lt;br&gt;

Comparison of biophysical characteristics and predicted thermophysiological responses of three prototype body armor systems versus baseline U.S. Army body armor systems &lt;br&gt;

Thermographic ranges of dromedary camels during physical exercise: applications for physical health/welfare monitoring and phenotypic selection.

Despite the relatively wide knowledge of camel biomechanics, research into the immediate functional response that accompanies the execution of physical exercise remains unapproached. Therefore, selective breeding programs lack an empirical basis to achieve genetic improvement of physical stress tolerance traits and monitor camel welfare in this regard. Given the fact that physical exercise increases net heat production, infrared thermography (IRT) was selected to study the temperature changes at the skin surface of the different body areas in clinically normal dromedary camels, mostly relegated to leisure activities. Specifically, a lower dispersion at the individual level of the surface temperature at the scapular cartilage region, shoulder joint, and pelvis region, as well as lower values for Tmax and Tmin at the region of the ocular region, pectoral muscles, semimembranosus-semitendinosus muscles, and hind fetlock after exercise, have to be considered as breeding criteria for candidate selection. Such thermophysiological responses can be used as indirect measures of tissue activity in response to exercise and hence are reliable indicators of animal tolerance to physical exercise-induced stress. Additionally, sex, castration, age, and iris pigmentation significantly impacted the thermo-physiological response to exercise in the study sample, which can be attributed to hormones, general vigor, and visual acuity-mediated effects. These specific factors' influence has to be considered for the evaluation of physical performance and the design of selection schemes for physical-related traits in dromedaries.

Mitigating heat effects in the workplace with a ventilation jacket: Simulations of the whole-body and local human thermophysiological response with a sweating thermal manikin in a warm-dry environment

Climate change is increasingly affecting human well-being and will inevitably impact on occupational sectors in terms of costs, productivity, workers’ health and injuries.Among the cooling garment developed to reduce heat strain, the ventilation jacket could be considered for possible use in workplaces, as it is wearable without limiting the user's mobility and autonomy.In this study, simulations with a sweating manikin are carried out to investigate the effects of a short-sleeved ventilation jacket on human thermophysiological responses in a warm-dry scenario.Simulations were performed in a climatic chamber (air temperature = 30.1 °C; air velocity = 0.29 m/s; relative humidity = 30.0 %), considering two constant levels of metabolic rate M (M1 = 2.4 MET; M2 = 3.2 MET), a sequence of these two (Work), and three levels of fan velocities (lf = 0; lf=2; lf=4).The results revealed a more evident impact on the mean skin temperature (Tsk) compared to the rectal temperature (Tre), with significant decreases (compared to fan-off) at all M levels, for Tsk from the beginning and for Tre from the 61st minute. Skin temperatures of the torso zones decreased significantly (compared to fan-off) at all M levels, and a greater drop was registered for the Back.The fans at the highest level (lf=4) were significantly effective in improving whole-body and local thermal sensations when compared to fan-off, at all M levels.At the intermediate level (lf=2), the statistical significance varied with thermal zone, M and time interval considered.The results of the simulations also showed that the Lower Torso needs to be monitored at M2 level, as the drop in skin temperature could lead to local overcooling and thermal discomfort.Simulations showed the potential effectiveness of the ventilation jacket, but human trials are needed to verify its cooling power in real working conditions.

Thermoregulation of human hands in cold environments and its modeling approach: A comprehensive review

Cold environments pose significant risks to human health, well-being, and productivity, with hands being particularly vulnerable to cold stress and injuries. Mathematical models of hand thermoregulation have emerged as valuable tools for understanding and predicting hand performance and injuries, especially in extremely cold environments. While significant progress has been made in mathematical modeling, a systematic review of these models is currently lacking. This paper aims to fill this knowledge gap by conducting a comprehensive review of the existing literature on hand thermoregulation models in cold environments. It begins with an introduction to the unique thermophysical and thermophysiological characteristics of the hand. It then summarizes the historical evolution of hand thermoregulation models. The essential principles for developing hand-specific thermoregulation models are outlined, encompassing modeling of hand anatomy and geometry, thermophysiological responses, and heat transfer between the hand and its surroundings. This review presents prediction methods for cold injuries and hand performance. The need for future advancements in hand thermoregulation modeling is emphasized. Specifically, achieving a more realistic representation of hand anatomy and geometry, as well as incorporating location-dependent thermophysical properties and physiological behaviors of the hand, are identified as crucial areas for improvement to enhance prediction accuracy. This review will contribute to a deeper understanding of hand thermoregulation mechanisms and their interaction with cold environments, as well as the development of more reliable and applicable models.

A multi-segment thermoregulatory model for predicting thermophysiological responses of sleeping body in various thermal conditions

This study presented a multi-segment thermoregulatory model to depict temperature distribution across the sleeping body. Taking into account the physiological characteristics during sleep, adjustments were made to a classical multi-segment model, including physiological parameters (i.e., metabolism, blood flow, set points of local skin and core temperatures) and thermoregulatory mechanisms (i.e., cutaneous vasomotion, sweating and shivering) considering the cycles of sleep stages and circadian rhythm. This sleeping thermoregulatory model was later validated against experimental data from published studies, encompassing a wide range of thermal conditions such as ambient temperature (3–32 °C), relative humidity (38–80 %) and bedding insulation (1.64–4.30 clo) including constant and transient environments. Results demonstrated the sleeping model's accurate perdition of whole-night local and mean skin temperatures under various thermal conditions. The average root-mean-square deviations of predicted mean skin temperatures for cold/cool, neutral, warm/hot, and transient conditions were 0.20 °C, 0.29 °C, 0.20 °C, and 0.19 °C, compared to the average standard deviations in the experimental data of 0.65 °C, 0.76 °C, 0.34 °C, and 0.61 °C, respectively. The sleeping model also showed significantly improved accuracy compared to the standard wake-state model with only adjustments in the basal metabolic rates and thermal insulations. In conclusion, this sleeping thermoregulatory model can effectively analyze the thermophysiological responses of the sleeping body, serving as a useful tool for evaluating thermal comfort of indoor environments and bedding settings.

Towards intelligent workstations: Investigating the feasibility of Doppler radar sensors for personal respiratory quantification in thermal comfort

Along the line of research efforts utilizing occupant thermophysiological responses in operation of Heating, Ventilation, and Air-Conditioning (HVAC), this study assessed feasibility of Doppler Radar Sensors (DRSs) in quantifying respiration. Respiration has been known as one of the physiological processes which gets adjusted based on metabolic rate and DRSs are capable of capturing characteristics of periodic movements of chest/abdomen area induced by respiration. Accordingly, we have devised two approaches of quantifying respiration in context of thermoregulation states – by checking (1) frequency and intensity of the signal representing respiration (i.e., respiration state) and (2) ratio between exhale and inhale (i.e., respiratory ratio). With these, two experimental studies have been conducted with human subjects to evaluate reliability, applicability/sensitivity. Results showed that 60 s of a measurement time could provide reliability, which opens a chance to eliminate a validation process and respiration might not be a physiological response that rapidly gets activated for heat adjustment. Also, it has been shown that, with sufficient acclimation time (20 min), five out of eight participants increased respiration states in a high temperature setup and seven out of eight participants raised their respiratory ratios. In other words, individuals have different ways of utilizing respiration to deal with heat adjustment and acclimation time plays a key role in the use of respiration. Given DRSs' conventional application is occupancy detection, the versatility of DRSs has been shown and it contributes to realizing an intelligent workstation that is capable of contextualizing user's behaviors and perceptions.

Topical application of isolated menthol and combined menthol-capsaicin creams: Exercise tolerance, thermal perception, pain, attentional focus and thermoregulation in the heat

ABSTRACT We determined the effects of topically applied (i) isolated menthol cream, (ii) menthol and capsaicin co-application or (iii) placebo cream on exercise tolerance, thermal perception, pain, attentional focus and thermoregulation during exercise in the heat. Ten participants cycled at 70% maximal power output until exhaustion in 35°C and 20% relative humidity after application of (i) 5% isolated menthol, (ii) 5% menthol and 0.025% capsaicin co-application or (iii) placebo cream. Thermo-physiological responses were measured during exercise, with attentional focus and pain determined post-exercise on a 0-to-10 scale. Across the three conditions, time to exhaustion was 13.4 ± 4.8 min, mean ± SD infrared tympanic and skin temperature was 37.2 ± 0.6°C and 35.1 ± 1.2°C, respectively, and heart rate was 152 ± 47 bpm, with no changes between conditions (p > 0.05). Perceived exertion was lower in the isolated menthol vs. all other conditions (p < 0.05, ηp2 = 0.44). Thermal sensation was higher in menthol-capsaicin co-application vs. isolated menthol (p < 0.05, d = 1.1), while sweat rate was higher for capsaicin and menthol co-application compared to menthol (p < 0.05, d = 0.85). The median and interquartile range scores for pain were lower (p < 0.05) in the menthol condition (8, 7-8) compared to both menthol and capsaicin (10, 9-10) and placebo (9, 9-10), which was coupled with a greater distraction (p < 0.05) in the menthol condition (9, 7-10) compared to placebo (6, 5-7). Despite no performance effects for any topical cream application condition, these data reiterate the advantageous perceptual and analgesic role of menthol application and demonstrate no advantage of co-application with capsaicin. Highlights Topical application of isolated menthol cream to cold-sensitive areas of the body during exhaustive exercise in the heat, elicited reduced perception of pain and enhanced sensation of cooling. While this reduction in generally unpleasant feelings (i.e. pain and heat) were coupled with lower RPE scores in the menthol condition and could be considered beneficial, there was no apparent ergogenic effect in an exercise tolerance test. Co-application of capsaicin and menthol appeared to inhibit the positive sensory effects elicited by menthol. Isolated menthol can induce changes in cognitive processes related to pain and exertion, while also reducing thermal sensation; however, the decision to use menthol creams must be balanced with the limited performance or thermoregulatory effects reported herein during exercise in hot environments.

Whole-Body Exposure System Using Horn Antennas With Dielectric Lens at 28 GHz

In the revised international guidelines and standard for human protection from electromagnetic fields, the permissible specific absorption rate (SAR) for whole-body exposure has been extended from 3 or 10 GHz to 300 GHz. The rationale for this revision is the extrapolation from findings of conventional radio-frequency exposure and infrared radiation. However, experiments of whole-body exposure in human subjects are limited to a few studies, which were conducted below 6 GHz. In this study, an exposure system at 28 GHz targeting a wide area of the human back was developed, which consists of two horn antennas with a dielectric lens. The effectiveness of the proposed exposure system was evaluated by computational dosimetry and experiments. The computed power absorption and measured distributions in the wave absorber and the back of the human subject were in good agreement. Under the compliance with the local exposure limits, the whole-body average SAR was 0.35 W/kg, which is comparable to the limit for whole-body exposure of 0.4 W/kg for occupational exposure in the international guidelines and standard. The developed exposure system would be useful to evaluate the thermophysiological response to whole-body exposure above 6 GHz.

Thermo-physiological responses and oxidative status of West African dwarf rams fed diets containing supplemental Tetrapleura tetraptera fruit meal

Plant secondary metabolites in Tetrapleuratetraptera fruit meal (TTFM) could be exploited as natural safe feed additives alternative to non- nutritive chemical and antibiotics to enhance rumen fermentation and feed utilization efficiency with negative oxidative stress. The study investigated the responses of West African Dwarf (WAD) rams to the diets containing varying levels of supplemental Tetrapleura tetraptera fruit meal on the oxidative status and thermo-physiological parameters. Thirty five (35) WAD rams with an average live weight of 13.20±0.2 kg were used in a completely randomized design for 140 days. Five concentrate diets containing varying levels (0, 0.5, 1.0, 1.5 and 2.0 %) of TTFM were formulated while Panicum maximum was fed as a basal diet. The rectal temperature, pulse rate and respiratory rate were measured at two week intervals while blood was collected through jugular veins at the onset and at the end of feeding trial to determine oxidative status parameters in terms of superoxide dismutase (SOD), glutathione peroxidase, thiobarbituric acid reactive substance (TBARS).Data collected were subjected to one way Analysis of Variance (ANOVA). No significant difference observed (p&gt;0.05) in the rectal temperature while the pulse rate and breathing rate increased significantly (p&lt;0.05) till 12th week of the experiment. Increased glutathione peroxidase, superoxide dismutase and lowered thiobarbituric acid reactive substance were recorded on the rams at the end of the feeding trial. It was therefore concluded that inclusion of Tetrapleura tetraptera up to 2 % level reduced the oxidative stress in the experimental animals coupled with better thermo-physiological responses

Estimation of the number of heat illness patients in eight metropolitan prefectures of Japan: Correlation with ambient temperature and computed thermophysiological responses.

The number of patients with heat illness transported by ambulance has been gradually increasing due to global warming. In intense heat waves, it is crucial to accurately estimate the number of cases with heat illness for management of medical resources. Ambient temperature is an essential factor with respect to the number of patients with heat illness, although thermophysiological response is a more relevant factor with respect to causing symptoms. In this study, we computed daily maximum core temperature increase and daily total amount of sweating in a test subject using a large-scale, integrated computational method considering the time course of actual ambient conditions as input. The correlation between the number of transported people and their thermophysiological temperature is evaluated in addition to conventional ambient temperature. With the exception of one prefecture, which features a different Köppen climate classification, the number of transported people in the remaining prefectures, with a Köppen climate classification of Cfa, are well estimated using either ambient temperature or computed core temperature increase and daily amount of sweating. For estimation using ambient temperature, an additional two parameters were needed to obtain comparable accuracy. Even using ambient temperature, the number of transported people can be estimated if the parameters are carefully chosen. This finding is practically useful for the management of ambulance allocation on hot days as well as public enlightenment.

Analysis of gravity effect on human blood flow and skin temperature through postural change

The blood flow of human body has much impact on the thermo-physiological response. When person change the posture, the gravity acts changes its direction and thus the blood flow can be changed. It is hypothesized that the gravitational effects of postural changes affect blood flow and skin temperature, which in turn affect comfort. To verify this, in the present study, a subject experiment focusing on postural changes was conducted for two conditions (Case 1 and Case 2). In the Case 1 experiment, the subjects were asked to raise their hands for 10 minutes after 30 minutes of rest in the chair-sitting position. As a result, significant skin temperature change were observed in the upper arm, forearm, and hand. The largest skin temperature change was observed in the hands, which showed a decrease in skin temperature of approximately 1.2 °C. The change had influence on the whole-body average value. In Case 2, the subjects were placed in the supine position for 10 minutes after 30 minutes of rest in the chair position. As a result, a decrease in skin temperature of approximately 1 °C was observed on the hands and 0.5 °C in the foot was observed.