Deep Body Temperature Research Articles

Physiological and perceptual responses of wearing a dryrobe for rewarming after passive cold-water immersion in men

ObjectivesTo investigate the physiological and perceptual responses to wearing a dryrobe for rewarming after passive cold-water immersion (CWI).Methods15 unhabituated healthy Caucasian men (age: 28.9 (5.4) years) attended the laboratory on...

Relationships of infrared thermography temperature with core temperature in goat.

Rectal temperature is widely used as an indicator of animal health. However, rectal temperature is conventionally measured by an invasive method, which may reduce animal welfare. So, this study aimed to determine the relationships between the deep-body (core) temperature and body surface temperatures in goats and develop a linear regression equation to establish the core temperature based on body surface temperatures. Body surface temperatures (head, eye, muzzle, horn, back, scrotum and groin) of goats were measured by infrared thermography (IRT). Ambient temperatures were measured by digital thermometer. Core temperatures were measured by a digital vet thermometer. Pearson correlation analysis was used to analyze the relationship between body surface temperatures, ambient temperature, and core temperature. Simple linear regression analysis was used to develop core temperature assessment equations. Correlation analysis showed that groin temperature was highly correlated with core temperature, and low correlated with ambient temperature. The body surface temperature of other region was low correlated with core temperature, and highly correlated with ambient temperature. Regression analysis showed that the determination coefficient of core temperature assessment equation based on groin temperature was the highest (P < 0.0001, R2 = 0.55), and those based on surface temperature of other regions were low (P < 0.01, R2 ≤ 0.16). We concluded that body surface temperatures obtained by IRT could be used for the assessment of goat core temperature. The core temperature assessment equations developed by the temperature of the body surface, which is less affected by ambient temperature, was found to have a higher determination coefficient than the equations developed using body surface temperature that is more affected by ambient temperature.

A new noninvasive technique for heat-flux-based deep body thermometry together with possible estimation of thermal resistance of the skin tissue.

A new noninvasive core-thermometry technique, based on the use of two heat flux sensors with different very low thermal resistances, is proposed. Thermodynamically derived equations, using a pair of skin temperatures and heat fluxes detected from the sensors, can give the estimated deep body temperature (DBT) together with thermal resistance of the skin tissue itself. The validity and accuracy of this method are firstly investigated through in vitro experiments using a tissue phantom model and, secondly, as in vivo comparisons with sublingual (Tsub) or rectal temperature (Trec) measurements in 9 volunteers, attaching the sensors around the upper sternum or the nape. Model experiments showed a good agreement between the measured and estimated temperatures, ranging from approximately 36 to 42 ℃. In vivo experiments demonstrated linear correlations between the estimated DBT and both Tsub and Trec values, though the estimated DBT was 0.13 ℃ higher than Tsub and 0.42 ℃ lower than Trec on average. The results also strongly suggested the possibility to estimate the tissue thermal resistance; this is discussed herein. Although further in vivo experiments under various environmental conditions are necessary, this method appears highly promising as an accurate, useful and convenient core-thermometry system for medical and healthcare settings.

Metagenomic Thermometer.

Various microorganisms exist in environments, and each of them has its optimal growth temperature (OGT). The relationship between genomic information and OGT of each species has long been studied, and one such study revealed that OGT of prokaryotes can be accurately predicted based on the fraction of seven amino acids (IVYWREL) among all encoded amino-acid sequences in its genome. Extending this discovery, we developed a 'Metagenomic Thermometer' as a means of predicting environmental temperature based on metagenomic sequences. Temperature prediction of diverse environments using publicly available metagenomic data revealed that the Metagenomic Thermometer can predict environmental temperatures with small temperature changes and little influx of microorganisms from other environments. The accuracy of the Metagenomic Thermometer was also confirmed by a demonstration experiment using an artificial hot water canal. The Metagenomic Thermometer was also applied to human gut metagenomic samples, yielding a reasonably accurate value for human body temperature. The result further suggests that deep body temperature determines the dominant lineage of the gut community. Metagenomic Thermometer provides a new insight into temperature-driven community assembly based on amino-acid composition rather than microbial taxa.

Flexible and Wireless Multipoint Epidermal Temperature Sensor

Measurement of body temperature is the most frequent medical screening performed in both hospital and domestic environments. Dual-heat-flux (DHF) thermometry provides an indirect method to estimate deep body temperature, which is unpractical and uncomfortable to be measured, from the easily accessible surface of the skin, by exploiting four temperature sampling points on a same device. This paper combines, for the first time, the DHF method with the flexible epidermal Ultra High Frequency (UHF) Radio Frequency IDentification (RFID) technology to replace bulky and wired state-of-the-art DHF devices. Four RFID Integrated Circuits (ICs) with embedded temperature sensors are used in place of the wired temperature probes so that they will be in charge of both sensing and wireless transmission of the data by means of four small antennas also embedded in the device. By integrating the antennas within elastomeric substrates, a highly conformable plaster-like device is achieved. It is flexible and soft, and can be read from a distance of more than 15 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</i> regardless of the curvature of the body region where it is placed, and also in case of moderate displacement (±5 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</i> ) with respect to the external interrogator.

Thermal modeling of the respiratory turbinates in arctic and subtropical seals

Mammals possess complex structures in their nasal cavities known as respiratory turbinate bones, which help the animal to conserve body heat and water during respiratory gas exchange. We considered the function of the maxilloturbinates of two species of seals, one arctic (Erignathus barbatus), one subtropical (Monachus monachus). By means of a thermo-hydrodynamic model that describes the heat and water exchange in the turbinate region we are able to reproduce the measured values of expired air temperatures in grey seals (Halichoerus grypus), a species for which experimental data are available. At the lowest environmental temperatures, however, this is only possible in the arctic seal, and only if we allow for the possibility of ice forming on the outermost turbinate region. At the same time the model predicts that for the arctic seals, the inhaled air is brought to deep body temperature and humidity conditions in passing the maxilloturbinates. The modeling shows that heat and water conservation go together in the sense that one effect implies the other, and that the conservation is most efficient and most flexible in the typical environment of both species. By controlling the blood flow through the turbinates the arctic seal is able to vary the heat and water conservation substantially at its average habitat temperatures, but not at temperatures around −40 °C. The subtropical species has simpler maxilloturbinates, and our model predicts that it is unable to bring inhaled air to deep body conditions, even in its natural environment, without some congestion of the vascular mucosa covering the maxilloturbinates. Physiological control of both blood flow rate and mucosal congestion is expected to have profound effects on the heat exchange function of the maxilloturbinates in seals.

Current status of active cooling, deep body temperature measurement, and face mask wearing in heat stroke and heat exhaustion patients in Japan: a nationwide observational study based on the Heatstroke STUDY 2020 and 2021.

The study aimed to determine the current status of face mask use, deep body temperature measurement, and active cooling in patients suffering from heatstroke and heat exhaustion in Japan. This was a prospective, observational, multicenter study using data from the Heatstroke STUDY 2020-2021, a nationwide periodical registry of heat stroke and heat exhaustion patients. Based on the Bouchama heatstroke criteria, we classified the patients into two groups: severe and mild-to-moderate. We compared the outcomes between the two groups and reclassified them into two subgroups according to the severity of the illness, deep body temperature measurements, and face mask use. Cramer's V was used to determine the effect sizes for a comparison between groups. Almost all patients in this study were categorized as having degree III based on the Japanese Association for Acute Medicine heatstroke criteria (JAAM-HS). However, the severe group was significantly worse than the mild-to-moderate group in outcomes like in-hospital death and modified Rankin Scale scores, when discharged. Heatstrokes had significantly higher rates of active cooling and lower mortality rates than heatstroke-like illnesses. Patients using face masks often use them during labor, sports, and other exertions, had less severe conditions, and were less likely to be young male individuals. It is suggested that severe cases require a more detailed classification of degree III in the JAAM-HS criteria, and not measuring deep body temperature could have been a factor in the nonperformance of active cooling and worse outcomes.

An Advanced Internet of Things System for Heatstroke Prevention with a Noninvasive Dual-Heat-Flux Thermometer.

Heatstroke is a concern during sudden heat waves. We designed and prototyped an Internet of Things system for heatstroke prevention, which integrates physiological information, including deep body temperature (DBT), based on the dual-heat-flux method. A dual-heat-flux thermometer developed to monitor DBT in real-time was also evaluated. Real-time readings from the thermometer are stored on a cloud platform and processed by a decision rule, which can alert the user to heatstroke. Although the validation of the system is ongoing, its feasibility is demonstrated in a preliminary experiment.

Relationship between body composition indices and changes in body temperature due to hot pack use

BackgroundHot pack application is used to reduce pain and muscle stiffness at the treated site. However, the effects of hot pack application on the whole body have not been clarified. We investigated the relationship between body composition indices and the hot pack-induced increase in body temperature.MethodsWe recruited 17 healthy men (age, 22.0 ± 3.3 years) who participated in the study on five different days and applied “dry” hot packs at four different sites (the most frequently used sites): right shoulder, lower back, both popliteal areas, and lower back plus popliteal areas. The study protocol involved the measurement of body composition followed by 10 min of bed rest, 15 min of warming with a hot pack, and 20 min of subsequent rest. Heart rate and body temperature were measured continuously, and blood pressure was recorded at 5-min intervals. Body temperature was measured at the right upper arm, precordium, abdomen, lumbus, right hallux, right femur, and right auditory canal.ResultsSkin temperature increased significantly at and near the hot pack application site, but this finding showed no relationship with body composition indices. The warmability distal to the application site was negatively correlated with the body water content index. The auditory canal temperature did not change in any of the sessions.ConclusionsHot pack usage alone did not increase the deep-body temperature and only increased the temperature around the application area. Moreover, higher body water content may allow for easier dissipation of heat from the peripheral extremities.

Kinetics of lipid indicators in response to short- and long-duration whole-body, cold-water immersion

Cold exposure-induced secretion of stress hormones activates cold-defense responses and mobilizes substrates for increased energy demands to fuel thermogenesis. However, it is unclear whether acute cold exposure-induced stress hormone response kinetics affect circulating lipid parameter kinetics. Therefore, we aimed to investigate the 2-day kinetics of stress hormones (i.e., cortisol, epinephrine, and norepinephrine) and the lipid profile (i.e., total cholesterol [TC], high-density lipoprotein [HDL] cholesterol, low-density lipoprotein [LDL] cholesterol, and triglycerides) in response to whole-body long- (intermittent 170 min; 170-CWI) or short-duration (10 min; 10-CWI) cold-water immersion (CWI; 14 °C water) in 17 healthy, young, adult men. Both CWI trials induced a marked release of the stress hormones, epinephrine, and norepinephrine, with higher concentrations detected after 170-CWI (p < 0.05) and a disrupted diurnal peak of cortisol lasting for a few hours. 170-CWI increased triglyceride levels from immediately after until 2 h after CWI, thereafter the concentration decreased at 4 h, 6 h, 1 day and 2 days after CWI (p < 0.05). Furthermore, the HDL-cholesterol level increased immediately after and at 6 h after 170-CWI (p < 0.05), while TC and LDL-cholesterol levels were not altered within 2 days. Lipid parameters were not affected within the 2 days after 10-CWI. Although both CWIs decreased deep body temperature and increased stress hormone levels for a few hours, only long-duration CWI induced changes in the circulating lipid profile within 2 days after CWI. This should be considered when discussing therapeutic protocols to improve circulating lipid profiles and ameliorate diseases associated with such profiles.

Human temperature regulation under heat stress in health, disease, and injury.

The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.

Passive Acoustic Thermometry of the Chest of a Person with COVID-19

Passive acoustic thermometry (PAT) was used to study the dynamics of changes in the chest temperature of a person with COVID-19 over the course of about two and a half weeks after quarantine. PAT, which can measure deep body temperature, showed that the integral temperature of tissues surrounding the lungs increased from 32.2 ± 0.07 to 33.0 ± 0.03°C about 10 days after the end of quarantine. This may indicate increased blood supply to the lungs, i.e., an indication of recovery. Infrared thermometry used to monitor recovery yielded no results.

Agreement of telemetric temperature capsules ingested 48 hours apart

Telemetric temperature capsules are frequently utilized to measure deep body temperature. Whereas most methods to measure temperature are conducted at a single site (e.g., rectal temperature), the location of ingested telemetry capsules varies. If distinct regions of the gastrointestinal tract have different temperatures, the measurements obtained using telemetry capsules will vary accordingly. This study examined the agreement of two telemetric temperature capsules in fifty-seven Army Ranger School students ingested 64 and 16 h before a cool weather waterborne movement. Twenty-one subjects (37%) (age: 25 ± 4, weight: 81±7 kg) retained both capsules. Subjects completed activities that could increase (e.g. exercise) and decrease (e.g. cold water immersion) body temperature. Agreement between the two capsules was assessed through concordance and Bland Altman analysis using a linear mixed model. Bias between the two capsules was low (0.01 °C, SE = 0.03, before a neck-deep immersion river crossing and −0.09 °C, SE = 0.08, after the river crossing), but there were large differences in the variance components (0.044 vs 0.155 total variance for the pre-crossing vs the post-crossing data). The 95% Limits of Agreement indicate that discordance between the two capsules was lower before the river crossing (−0.40 to +0.42 °C) than after (−0.86 to +0.68 °C). In summary, this study examined telemetry capsule agreement with more time between capsule ingestion (48 h) in a larger sample size than most previous studies on the topic, and found notable (95% LoA>0.4 °C) variability between the two capsules which was exacerbated after crossing a cold river. Differences in gastrointestinal location of telemetry capsules can introduce variability into the measurement of deep body temperature due to regional temperature differences. This variability may be acceptable for some study designs, but unacceptable when small changes in temperature are important to detect. If the convenience of telemetric temperature capsules is desired, an alternative is to use the capsule as a rectal suppository.

Application of tight-fitting half-facepiece breath-response powered air-purifying respirator for internal body cooling in occupational environment.

In dust-generating scenarios in occupational environments, it is important to take measures to prevent not only pneumoconiosis, but also heatstroke. The aim of this study was to verify whether using a tight-fitting half-facepiece breath-response powered air-purifying respirator (PAPR) in combination with a self-produced cooling device could abate the deep body temperature while performing activities. We conducted a crossover study involving 10 subjects. The subjects were subjected to three conditions: wearing a PAPR equipped with a cooling device, PAPR, or a replaceable particulate respirator. During the experiment, the rectal temperature of the subjects was measured, along with the temperature near the PAPR inlet in container with the cooling device when the PAPR equipped with the cooling device was worn. The subjects rested in a cold chamber set at a dry-bulb temperature of 28°C and relative humidity of 45% for 20 min. Then, they moved to a hot chamber set to a dry-bulb temperature of 36°C (with the same relative humidity) in 5 min and exercised on a cycle ergometer for 30 min. After that, the subjects moved to the cold chamber for 5 min and rested for 20 min. Notably, the air inhaled by the subjects wearing PAPR equipped with the cooling device was approximately 10°C cooler than the ambient air. Furthermore, 35 min after the initiation of the experiment (after the middle of the exercise period), the rectal temperature of the participants wearing the PAPR equipped with the cooling device was lower than of those wearing PAPR or replaceable particulate respirators (p <0.05). Thus, we could deduce that the self-produced cooling device was useful in abating deep body temperature. PAPR is useful for its potential applications in hot occupational environments and can save lives in working environments where heat stress can result in major medical complications.

Predicting Deep Body Temperature (Tb) from Forehead Skin Temperature: Tb or Not Tb?

There is a need to rapidly screen individuals for heat strain and fever using skin temperature (Tsk) as an index of deep body temperature (Tb). This study’s aim was to assess whether Tsk could serve as an accurate and valid index of Tb during a simulated heatwave. Seven participants maintained a continuous schedule over 9-days, in 3-day parts; pre-/post-HW (25.4 °C), simulated-HW (35.4 °C). Contact thermistors measured Tsk (Tforehead, Tfinger); radio pills measured gastrointestinal temperature (Tgi). Proximal-distal temperature gradients (ΔTforehead–finger) were also measured. Measurements were grouped into ambient conditions: 22, 25, and 35 °C. Tgi and Tforehead only displayed a significant relationship in 22 °C (r: 0.591; p < 0.001) and 25 °C (r: 0.408; p < 0.001) conditions. A linear regression of all conditions identified Tforehead and ΔTforehead–finger as significant predictors of Tgi (r2: 0.588; F: 125.771; p < 0.001), producing a root mean square error of 0.26 °C. Additional residual analysis identified Tforehead to be responsible for a plateau in Tgi prediction above 37 °C. Contact Tforehead was shown to be a statistically suitable indicator of Tgi in non-HW conditions; however, an error of ~1 °C makes this physiologically redundant. The measurement of multiple sites may improve Tb prediction, though it is still physiologically unsuitable, especially at higher ambient temperatures.

The Hypothermic Effect of Hydrogen Sulfide Is Mediated by the Transient Receptor Potential Ankyrin-1 Channel in Mice.

Hydrogen sulfide (H2S) has been shown in previous studies to cause hypothermia and hypometabolism in mice, and its thermoregulatory effects were subsequently investigated. However, the molecular target through which H2S triggers its effects on deep body temperature has remained unknown. We investigated the thermoregulatory response to fast-(Na2S) and slow-releasing (GYY4137) H2S donors in C57BL/6 mice, and then tested whether their effects depend on the transient receptor potential ankyrin-1 (TRPA1) channel in Trpa1 knockout (Trpa1−/−) and wild-type (Trpa1+/+) mice. Intracerebroventricular administration of Na2S (0.5–1 mg/kg) caused hypothermia in C57BL/6 mice, which was mediated by cutaneous vasodilation and decreased thermogenesis. In contrast, intraperitoneal administration of Na2S (5 mg/kg) did not cause any thermoregulatory effect. Central administration of GYY4137 (3 mg/kg) also caused hypothermia and hypometabolism. The hypothermic response to both H2S donors was significantly (p < 0.001) attenuated in Trpa1−/− mice compared to their Trpa1+/+ littermates. Trpa1 mRNA transcripts could be detected with RNAscope in hypothalamic and other brain neurons within the autonomic thermoeffector pathways. In conclusion, slow- and fast-releasing H2S donors induce hypothermia through hypometabolism and cutaneous vasodilation in mice that is mediated by TRPA1 channels located in the brain, presumably in hypothalamic neurons within the autonomic thermoeffector pathways.

Proof-of-Concept for the Analgesic Effect and Thermoregulatory Safety of Orally Administered Multi-Target Compound SZV 1287 in Mice: A Novel Drug Candidate for Neuropathic Pain.

SZV 1287 (3-(4,5-diphenyl-1,3-oxazol-2-yl)propanal oxime) is a novel multi-target candidate under preclinical development for neuropathic pain. It inhibits amine oxidase copper containing 3, transient receptor potential ankyrin 1 and vanilloid 1 (TRPV1) receptors. Mainly under acidic conditions, it is transformed to the cyclooxygenase inhibitor oxaprozin, which is ineffective for neuropathy. Therefore, an enterosolvent capsule is suggested for oral formulation, which we investigated for nociception, basic kinetics, and thermoregulatory safety in mice. The antihyperalgesic effect of SZV 1287 (10, 20, 50, and 200 mg/kg, p.o.) was determined in partial sciatic nerve ligation-induced traumatic neuropathy by aesthesiometry, brain and plasma concentrations by HPLC, and deep body temperature by thermometry. Its effect on proton-induced TRPV1 activation involved in thermoregulation was assessed by microfluorimetry in cultured trigeminal neurons. The three higher SZV 1287 doses significantly, but not dose-dependently, reduced neuropathic hyperalgesia by 50% of its maximal effect. It was quickly absorbed; plasma concentration was stable for 2 h, and it entered into the brain. Although SZV 1287 significantly decreased the proton-induced TRPV1-mediated calcium-influx potentially leading to hyperthermia, it did not alter deep body temperature. Oral SZV 1287 inhibited neuropathic hyperalgesia and, despite TRPV1 antagonistic action and brain penetration, it did not influence thermoregulation, which makes it a promising analgesic candidate.

Acetylcholinesterase Inhibition Attenuates Lipopolysaccharide‐Induced Hypotension in Unanesthetized Hypertensive Rats

Background Hypertension and sepsis are highly prevalent clinical risk factors for morbidity and mortality. Administration of lipopolysaccharide (LPS) induces systemic inflammation (SI) and phathophysiological changes observed during sepsis, such as exacerbated release of inflammatory markers associated with hypotension, tachycardia, and hypothermia followed by fever. We have previously shown that both LPS-induced hypothesion and hypothermia are enhanced in hypertensive rats. Increased availability of acetylcholine may reduce inflammation. However, whether acetylcholinesterase inhibition modulates SI and its cardiovascular and thermorregulatory consequences in neurogenic hypertension remains unkonwn. Aim This study aimed to investigate the putative anti-inflammatory property of pyridostigmine (PIR), an acetylcholinesterase inhibitor, on cardiovascular and thermoregulatory changes observed during LPS-induced SI (at a septic-like model) in spontaneously hypertensive rats (SHR). Methods Wistar and SHR rats were used in the present study. Forty-eight hours before cardiovascular and deep body temperature (Tb) recordings, the animals underwent the surgery for femoral artery (for direct hemodynamic recordings) and vein catheterization for PIR (0.25 mg kg-1), LPS (1.5mg kg−1), or saline administration. In the same surgical procedure, an intraperitoneal temperature data-logger capsule was inserted for Tb recordings. We combined hemodynamic and thermoregulatory recordings after LPS administration and plasma measurements of interleukin (IL)-1β and IL-6. Results SI in Wistar rats was marked by a drop in blood pressure (2 ± 2 vs. −12 ± 2 mmHg, P < 0.0001). Compared with Wistar, LPS-induced drop in blood pressure was higher in SHR (−44 ± 4 vs. 2 ± 2 mmHg, P < 0.0001). PIR attenuated LPS-induced hypotension in Wistar (-12 ± 2 vs. 4 ± 3 mmHg, P = 0.0048) and SHR rats (-44 ± 4 vs. -23 ± 4 mmHg, P = 0.0016). LPS induced hypothermia followed by fever in Wistar rats (37.5 ± 0.2 vs. 38.9 ± 0.2ºC, P < 0.0001), whereas, in SHR, a maintained hypothermia without fever was observed (36.4 ± 0.2ºC). PIR attenuated fever in Wistar rats (38.9 ± 0.2 vs. 38.0 vs. 0.2ºC, P = 0.0015), but did not affect LPS-induced hypothermia in SHR (36.6 ± 0.1ºC). After LPS administration, Wistar rats showed significant plasma IL-1β (1393 ± 218 vs. 49 ± 12 pg mL−1, P < 0.0001) and IL-6 surges (44732 ± 5870 vs. 144 ± 13, P < 0.0001), and this increase was prevented by PIR pretreatment (1393 ± 218 vs. 430 vs. 98 pg mL−1, P = 0.0018 and 44732 ± 5870 vs. 18280 vs. 4123 pg mL−1, P = 0.0438). This anti-inflammatory effect of PIR was not observed in SHR. Conclusion The findings of the present study are consistent with the notion that pretreatment with an acetylcholinesterase inhibitor (PIR) attenuates the plasma IL-1β and IL-6 surges, hypotension, and fever in Wistar rats. On the other hand, PIR attenuated hypotension without preventing hypothermia, and plasma pro-inflammatory cytokines surges in SHR. We suggest that increased acetylcholine availability reduces LPS-induced SI in Wistar, but not in SHR. These findings reveal a novel effect of acetylcholinesterase inhibition during SI in normotensive and hypertensive rats.

The effect of body surface area exposure to menthol on temperature regulation and perception in men.

In warm conditions topical application of menthol increases cool sensations and influences deep body temperature. The purpose of this experiment was to explore whether different body surface areas (BSA) exposed to menthol influence these responses. It was hypothesized that the forcing function exerted by menthol will be proportionally related to BSA. Using a within-participant design, 13 participants underwent three BSA exposures (Small [S; finger]; Medium [M; arm]; Large [L; upper/lower body]) to 4.13% menthol, and one Placebo exposure. During each exposure participants rested supine in a tent (30°C, 50%rh) for 30-min before their intervention and 30-min thereafter. Measures included thermal sensation, thermal comfort, irritation, skin blood flow (finger SkBF; laser Doppler flowmetry), rectal temperature (Tre), and skin temperature (chest, forearm, thigh, calf). The Area Under the Curve from minute 30 to 60 was calculated and analyzed using a one-way ANOVA or Friedman's test with post-hoc testing (0.05 alpha level). There was no significant difference in any measure of thermometry (p>0.05), while SKBF was significantly lowered in L, M, and S vs. P respectively (p<0.05). Participants in L felt cooler vs. P and S (p<0.05). Losses in thermal comfort were noted in L and M vs. P and S (p<0.05), along with increased irritation in L vs. S (p<0.05). Despite similar skin temperatures, larger BSA's exposed to menthol caused cooler sensations, likely due to the activation of a larger pool of menthol-sensitive neurons. This occurred in the absence of thermal discomfort and without perceptions of irritation exceeding 'weak'. Larger BSA's also exhibited greater alterations in Tre, likely driven by a reduction in SkBF, but despite this mean body temperature was regulated suggesting the thermoregulatory system can cope with the range of BSA exposures studied herein.

Perceived Thermal Response of Stone Quarry Workers in Hot Environment

Introduction: Impact of heat on health of workers goes unrecognized by the virtue of the indispensable fact that every individual has varied perception and tolerance capacity. The present study determine the physiological signs with perceived subjective responses under the thermal stress.Materials and Methods: The study was spread on open field stone quarry workers (N = 934) during the summer (May to June), post monsoon (September to October), and winter (December to January).Results: In the summer months, dry bulb temperature range from 36.1 to 43.2°C and the distribution of Wet Bulb Globe temperature (WBGT) outdoor values were outlier-prone than normal distribution indicated heat vulnerability. The environmental effect on weighted average skin temperature (Tsk) local segmental Tsk and deep body temperature (Tcr) were greater than the effects that might be attributed to work severity. The tolerance time level in summer months (65 ± 13 min at WBGT 35 ± 2.3°C) was less than in other two season. About 85% of workers in summer, 68% in post monsoon and 79% in winter recorded working heart rate greater than 90 beats/min. Physiological and subjective responses to heat stress indicated that during summer month the workers complained of excessive sweating (93.5%), feeling of thirst/dry mouth (88.7%), elevated Core temperature (Tcr) (58.7%) and decreased working capacity (75.6%). The observation found that around 14% workers were vulnerable to heat stress and the workers had no knowledge to mitigate the heat related illnesses.Discussion and Conclusions: The stone quarry work as compared to other outdoor workers have environmental adversaries which becomes confounding variables in the study of such occupations. There was significant difference (p &amp;lt; 0.001) as far as the physiological and thermoregulatory responses were concerned in three different months of investigation.