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Purpose: This study aimed to characterize core-temperature (Tc) responses of swimmers competing at the 2024 3-km World Aquatics Masters Open Water Swimming Championships. Methods: Within a cross-sectional observational study design, swimmers (n = 48 [23 male, 25 female]) ingested a telemetric Tc pill 4 hours before their race. Water temperatures were 20.9 °C (male; mean wet-bulb-globe temperature 25.9 °C) and 20.5 °C (female; mean wet-bulb-globe temperature: 25.4 °C). Linear mixed models determined differences between males and females for race-start, mean in-race, and peak Tc. Random coefficient models determined relationships between (1) sex, race time, body mass index (BMI), body-mass change or age, and Tc peak; (2) sex, race time, BMI, body-mass change or age, and Tc nadir; (3) sex, Tc peak, BMI, body-mass change or age, and race time, and (4) sex, Tc peak, BMI, body-mass change, or age and race ranking. Results: The mean in-race Tc was 37.8 °C (36.1–38.8 °C); however, there were highly variable individual Tc responses (−3.1 to +2.7 °C). One swimmer experienced mild hypothermia (Tc ≤ 35.0 °C), and 5 exceeded 39.0 °C, a risk factor for heat-related illness. There were no statistical differences between males and females for race-start, mean, and peak Tc (P ≥.243). Higher peak Tc was associated with faster race time (P =.05), higher race rank (P =.027), and higher BMI (P =.001). Conclusions: Highly variable Tc responses (−3.1 to +2.7 °C) were observed, demonstrating that organizers of mass-participation open-water swimming events should always be prepared for, and provide facilities to treat, swimmers experiencing cold-/heat-related health incidents during competition. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated associations between environmental temperatures and match running performance in 4 professional football leagues. Methods: Running performance indicators including total, high-speed, and sprint distances were collated from 1610 matches from the German Bundesliga 1 and 2, Japanese J-League, and Turkish SüperLig. Environmental data for each of these matches were obtained for dry-bulb and wet-bulb globe temperatures (WBGT) retrospectively from public sources. Linear regressions were used to determine relationships between running performance indicators and both temperature and WBGT for individual leagues. Furthermore, linear mixed models were used to determine associations across all 4 leagues, accounting for differences between them as random effects. Bonferroni corrections were applied to account for multiple tests. Results: Overall, combined-league data showed that total distance (95% CI, −0.50 to 0.37; β: −0.36), number of high-speed runs (95% CI, −4.57 to 2.93; β: −0.29), high-speed distances (95% CI, −0.07 to 0.05; β: −0.28), number of sprints (95% CI, −2.72 to 2.07; β: −0.39), and sprint distances (95% CI, −0.05 to 0.03; β: −0.22) were all lower when WBGT was higher (P <.001), whereas the peak speed recorded per match (95% CI, 0.01 to 0.03; β: 0.18) was higher when WBGT was higher (P <.001). Models with temperature instead of WBGT derived similar results. Conclusion: Warmer environmental conditions were associated with lower total, high-speed, and sprint distances covered. These responses may result from an increased thermoregulatory load or indirectly from an adapted individual or team-tactical pacing strategy in warmer conditions. Teams should consider strategies to counter such effects to avoid lower distances covered at high intensities that are related to success in football. [ABSTRACT FROM AUTHOR]

Purpose: The current study aimed to determine the effect of a synthetic-grass sport surface on core body temperature, skin temperature, heart rate, thermal sensation, thermal comfort, and rating of perceived exertion (RPE) during intermittent exercise in hot conditions. Methods: Using a randomized crossover design, 13 trained/developmental team-sport athletes completed two 50-minute standardized intermittent running protocols on a synthetic and a natural-grass surface, on separate days (control-condition air temperature 32.6 °C [1.3 °C], relative humidity 43.2% [5.3%]). Results: Final skin temperature was significantly higher on synthetic compared with natural grass at the calf (40.1 °C [2.5 °C] vs 33.4 °C [0.6 °C]; P <.001), shoulder (36.6 °C [1.7 °C] vs 33.7 °C [0.7 °C]; P <.001), and chest (33.2 °C [1.1 °C] vs 31.8 °C [1.2 °C]; P =.02). Thermal sensation (median: 2.3; interquartile range [0.5] vs 2.2 [0.5], P =.03) and sweat rate (1.5 [0.4] L·h−1 vs 1.2 [0.3] L·h−1; P =.02) were also significantly higher on synthetic grass. While final core body temperature was significantly higher on the natural than synthetic grass (38.4 °C [0.3 °C] vs 38.2 °C [0.4 °C]), there were no significant differences in delta core temperature, as well as heart rate, thermal comfort, or RPE. Conclusions: Higher skin temperatures, thermal sensation, and sweat rates suggest that exercising on synthetic grass in hot conditions may increase some markers of heat strain during exercise. However, delta core body temperature, heart rate, thermal comfort, and RPE remained unaffected. [ABSTRACT FROM AUTHOR]

The detrimental impact of extreme heat exposure on the health and well-being of children is widely acknowledged. The direct and indirect effects of climate change have led to an increased risk of certain cardiovascular events which may be particularly harmful to children who are born with, or develop, heart disease. Purpose: To highlight the worrying paucity of investigative research aimed at differentiating how higher ambient temperatures further tax an already compromised cardiovascular system in children. Methods: This commentary describes basic thermoregulatory concepts relevant to the healthy pediatric population and summarizes common heart diseases observed in this population. Results: We describe how heat stress and exercise are important factors clinicians should more readily consider when treating children with heart disease. Countermeasures to physical inactivity are suggested for children, parents, clinicians, and policymakers to consider. Conclusions: As sudden, excessive heat exposures continue to impact our rapidly warming world, vulnerable populations like children with underlying heart conditions are at greater heat health risk, especially when coupled with the negative physical activity and fitness trends observed worldwide. [ABSTRACT FROM AUTHOR]

This study sought to investigate the effect of cold ambient temperature on subcutaneous abdominal adipose tissue (SCAAT) lipolysis and blood flow during steady-state endurance exercise in endurance-trained cyclists. Ten males (age: 23 ± 3 years; peak oxygen consumption: 60.60 ± 4.84 ml·kg−1·min−1; body fat: 18.4% ± 3.5%) participated in baseline lactate threshold (LT) and peak oxygen consumption testing, two familiarization trials, and two experimental trials. Experimental trials consisted of cycling in COLD (3 °C; 42% relative humidity) and neutral (NEU; 19 °C; 39% relative humidity) temperatures. Exercise consisted of 25 min cycling at 70% LT and 25 min at 90% LT. In situ SCAAT lipolysis and blood flow were measured via microdialysis. Heart rate, core temperature, carbohydrate and fat oxidation, blood glucose, and blood lactate were also measured. Heart rate, core temperature, oxygen consumption, and blood lactate increased with exercise but were not different between COLD and NEU. SCAAT blood flow did not change from rest to exercise or between COLD and NEU. Interstitial glycerol increased during exercise (p <.001) with no difference between COLD and NEU. Fat oxidation increased (p <.001) at the onset of exercise and remained elevated thereafter with no difference between COLD and NEU. Carbohydrate oxidation increased with increasing exercise intensity and was greater at 70% LT in COLD compared to NEU (p =.030). No differences were observed between conditions for any other variable. Cycling exercise increased SCAAT lipolysis but not blood flow. Ambient temperature did not alter SCAAT metabolism, SCAAT blood flow, or fat oxidation in well-trained cyclists, though cold exposure increased whole-body carbohydrate oxidation at lower exercise intensities. [ABSTRACT FROM AUTHOR]

The aim of this audit was to quantify female representation in research on heat adaptation. Using a standardized audit tool, the PubMed database was searched for heat adaptation literature from inception to February 2023. Studies were included if they investigated heat adaptation among female and male adults (≥18–50 years) who were free from noncommunicable diseases, with heat adaptation the primary or secondary outcome of interest. The number and sex of participants, athletic caliber, menstrual status, research theme, journal impact factor, Altmetric score, Field-Weighted Citation Impact, and type of heat exposure were extracted. A total of 477 studies were identified in this audit, including 7,707 participants with ∼13% of these being female. Most studies investigated male-only cohorts (∼74%, n = 5,672 males), with ∼5% (n = 360 females) including female-only cohorts. Of the 126 studies that included females, only 10% provided some evidence of appropriate methodological control to account for ovarian hormone status, with no study meeting best-practice recommendations. Of the included female participants, 40% were able to be classified to an athletic caliber, with 67% of these being allocated to Tier 2 (i.e., trained/developmental) or below. Exercise heat acclimation was the dominant method of heat exposure (437 interventions), with 21 studies investigating sex differences in exercise heat acclimation interventions. We recommend that future research on heat adaptation in female participants use methodological approaches that consider the potential impact of sexual dimorphism on study outcomes to provide evidence-based guidelines for female athletes preparing for exercise or competition in hot conditions. [ABSTRACT FROM AUTHOR]

Background: Repeated exposure to heat (ie, plasma volume expansion) or altitude (ie, increase in total hemoglobin mass), in conjunction with exercise, induces hematological adaptations that enhance endurance performance in each respective environment. Recently, combining heat and altitude training has become increasingly common for athletes preparing to compete in temperate, sea-level conditions. Purpose: To review the physiological adaptations to training interventions combining thermal and hypoxic stimuli and summarize the implications for temperate, sea-level performance. Current Evidence: To date, research on combining heat and hypoxia has employed 2 main approaches: simultaneously combining the stressors during training or concurrently training in the heat and sleeping at altitude, sometimes with additional training in hypoxia. When environmental stimuli are combined in a training session, improvements in aerobic fitness and time-trial performance in temperate, sea-level conditions are generally similar in magnitude to those observed with heat, or altitude, training alone. Similarly, training in the heat and sleeping at altitude does not appear to provide any additional hematological or nonhematological benefits for temperate; sea-level performance relative to training in hot, hypoxic, or control conditions. Conclusions: Current research regarding combined heat and altitude interventions does not seem to indicate that it enhances temperate, sea-level performance to a greater extent than "traditional" (heat or hypoxia alone) training approaches. A major challenge in implementing combined-stressor approaches lies in the uncertainty surrounding the prescription of dosing regimens (ie, exercise and environmental stress). The potential benefits of conducting heat and altitude exposure sequentially (ie, one after the other) warrants further investigation. [ABSTRACT FROM AUTHOR]

The physiological mechanisms involved in augmented cholinergic agonist-induced sweating in exercise-trained individuals remain unclear. This study hypothesizes that nitric oxide synthase (NOS) contributes to augmented pilocarpine-induced sweating in habitually exercise-trained individuals. Endurance-trained and untrained men (n = 15 each) iontophoretically received 1% L-NAME, a NOS inhibitor, and saline (control) in the forearm and then administered 0.001% and 1% pilocarpine to evaluate sweat rate. L-NAME administration attenuated pilocarpine-induced sweating by 10% in the exercise-trained (P = 0.004) but not in untrained (P = 0.764) groups independent of pilocarpine concentrations. Results indicate that NOS partially contributes to increased cholinergic sweating in exercise-trained men. [ABSTRACT FROM AUTHOR]

Understanding physiological mechanisms of tolerance to heat exposure, and potential ways to improve such tolerance, is increasingly important in the context of ongoing climate change. We discuss the concept of heat tolerance in humans and experimental models (primarily rodents), including intracellular mechanisms and improvements in tolerance with heat acclimation. [ABSTRACT FROM AUTHOR]

Factors explaining individual variations in whole body sweat sodium ion concentration ([Na+]) during exercise are not fully understood. Galvanic skin conductance (GSC) reflects the electrical properties of the skin influenced by sweat rate (SR) and the presence of ions. Initiation of increases in this response to elevating sweating may reflect exceeding the maximal capacity of sweat ion reabsorption in sweat glands. We investigated whether the SR threshold for increasing GSC, an indirect measure of maximum ion reabsorption rates of sweat glands, explains the variations in whole body sweat [Na+]. Thirty young healthy males cycled for 90 min at incremental exercise intensities of 30, 45, and 60% peak oxygen uptake (30 min each) in the heat (32°C, 50% relative humidity). Whole body sweat [Na+] was measured using a whole body washdown technique. The SR threshold for increasing GSC was determined from the relationship between the local SR (ventilated capsule) and GSC on the forearm and chest. The average whole body sweat [Na+] was 42.8 ± 18.9 (range: 14.4–81.0) mmol L−1, and the SR threshold for increasing GSC was 0.29 ± 0.20 (range: 0.02–0.62) and 0.35 ± 0.30 (range: 0.01–1.40) mg cm−2 min−1 for the forearm and chest, respectively. Whole body sweat [Na+] was not correlated with the SR threshold for increasing GSC in the forearm or chest (r2 ≤ 0.001, P ≥ 0.921). We conclude that the SR threshold for increasing GSC at the forearm and chest does not explain the individual variation in whole body sweat [Na+] during exercise in the heat. NEW & NOTEWORTHY: Galvanic skin conductance is influenced by sweat rate and sweat ions, and the sweat rate at which this response begins to increase may reflect the exceeding capacity of sweat ion reabsorption in sweat glands. However, we show that this indirect measure of the sweat gland's capacity of ion regulation on the forearm and chest does not correlate with whole body sweat sodium concentration during exercise, excluding its role as a determinant of systemic sweat sodium loss. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate changes in the thermoregulatory mechanisms of juvenile yellowfin tuna, Thunnus albacares, with increasing body size by using archival tag data from 28 fish released in Japanese waters (fork length [FL] 35–92 cm). Fish with a body size of 35 cm FL remaining within the surface waters had lower thermal excess (0.4 °C), and fish with a body size of 40–60 cm FL undertaking brief diving at depths > 100 m had higher thermal excess (0.5–1.0 °C). However, the thermal excess did not consistently increase with body size, as has been reported for bigeye tuna. Heat budget models indicated inconsistent trends of decreased or increased heat production with body size. Yellowfin tuna regulate body temperatures by controlling the whole-body heat-transfer coefficient (λ) by 1.2–2.0 fold during descents and ascents, independent of body size, restricting λ for thermo-conservation during descent and increasing λ to absorb ambient heat during ascent. Compared with bigeye tuna, the vertical distributions of juvenile yellowfin tuna were limited to surface waters because of less efficient physiological thermoregulatory mechanisms. However, deep dives exceeding 1000 m, probably for predator avoidance, accompanied by rest in surface waters to recover from unusually higher behavioral activity, and vertical behavior similar to bigeye tuna "characteristic behavior" were observed. Compared to the thermoregulatory mechanisms of other tunas, those of juvenile yellowfin tuna are considered to be adaptive to tropical and subtropical shallower waters. [ABSTRACT FROM AUTHOR]

Purpose: Cold water immersion (CWI) is the most effective treatment for exertional heat stroke (EHS). However, knowledge on core temperature response during CWI treatment and the relation with patient characteristics (i.e., sex, anthropometrics) is limited. Therefore, the current study aimed to examine the core temperature response (in °C) during CWI treatment of recreational athletes participating in large running events and investigate the impact of sex and anthropometric characteristics on the cooling rate (in °C·min−1). Methods: This observational study includes 57 athletes (n = 22 females; 39%) who suffered from EHS during an exercise event in the Netherlands. After admission to the medical facilities, a rectal temperature (T rec) probe was inserted and all clothing was removed before immersion in an ice bath (6.4 ± 1.6°C). Rectal temperature was continuously measured throughout treatment, and treatment was continued until T rec ≤ 38.9°C or based on the decision of the emergency physician. Results: Initial T rec did not differ between males (41.3 ± 0.9°C) and females (41.2 ± 0.8°C, P = 0.83). A nonlinear response to CWI was observed, with the decrease in T rec beginning after 6 min of CWI. The decrease in T rec did not differ between both sexes (ptime*sex = 0.96). The cooling rate did not differ between males (0.21 ± 0.15°C·min−1) and females (0.19 ± 0.08°C·min−1, P = 0.55), and was not related to body mass, body surface area and body surface area to mass ratio (all P values >0.05). Conclusions: We demonstrated that the cooling rate during CWI did not differ between men and women suffering from EHS, and that the T rec response to CWI is nonlinear and not dependent on anthropometric characteristics. This suggests that no sex differentiation is needed in the EHS treatment guidelines and confirms the necessity to continuously monitor T rec during treatment. [ABSTRACT FROM AUTHOR]

The purpose of this study is to compare the effects of two different ways of stopping incubator humidification on episodes of hypothermia, hyperthermia, hyponatraemia, hypernatraemia, or skin injury. The design is a single site, two-armed, parallel, randomised, clinical trial conducted between April 2019 and March 2022. The setting was a quaternary referral and teaching hospital in Queensland, Australia. There were 140 extremely preterm infants, born < 28 weeks gestational age (GA). Intervention groups were (1) cease humidity: incubator humidification turned from 80% to off at 00.01am on day 8 of life (n = 70); or (2) gradually reduce humidity: incubator humidification reduced by 5% at 00:01 of each day from day 8 until ceased on day 14 (n = 70). The primary outcome was episodes of temperature instability: defined as either hypothermia < 36.5 °C or hyperthermia > 37.5 °C. Secondary outcomes included episodes of hyponatraemia: hypernatraemia or skin injury. One hundred forty infants were enrolled, 70 in each group. No statistically significant differences for any outcomes. Hyperthermia: 77% (n = 54) in the cease group and 73% (n = 51) in the gradual reduction group (P = 0.70). Hypothermia: 53% (n = 37) in the cease group and 37% (n = 26) in the gradual reduction group (P = 0.09). The number of hyponatraemic events was similar for both groups (P = 0.73), as for hypernatraemic events (P = 0.3). Skin injury in week 2 of life: 63% in the cease group and 67% in the gradual reduction group (P = 0.72). Conclusions: Ceasing or gradually reducing incubator humidification after day 7 of life had no effect on the number of episodes of hypothermia or hyperthermia in this cohort of extremely preterm infants (EPTI). There was also no effect on the number of episodes of hyponatraemia or hypernatraemia. Trial registration: ANZCTR.org.au (Australia New Zealand Clinical Trials Registry). ACTRN 1261 9000 266167 Registered 21/2/2019. What is Known: • Incubator humidification is a widely accepted and routine practice in the management of EPTI as it influences transepidermal water loss (TEWL) and supports thermoregulation. However, weaning practices remain varied and inconsistent across the globe. • There remains a paucity of data to inform specific evidenced-based humidification practices. What is New: • Ceasing or gradually reducing incubator humidification after 7 days had no effect on temperature stability, serum sodium levels, or frequency of skin injury in this cohort of EPTI between day 8 and day 14. • There is no apparent benefit in prolonging incubator humidity beyond day 7 of life in these EPTI. [ABSTRACT FROM AUTHOR]

This study investigated the impact of multiple nerve block methods (local anesthesia, conventional radiofrequency thermocoagulation [CRF], and pulsed radiofrequency [PRF]) on thermoregulation. Focusing on hypothalamic function, the effects of local anesthesia, CRF, and PRF on central and peripheral temperatures were analyzed and compared. Our findings revealed that all three nerve block groups cause a decrease in central temperature, with the CRF group exhibiting the most pronounced effect. Furthermore, immunostaining analysis showed decreased neural activity in the preoptic area, suggesting that nerve blocks may influence central thermoregulatory mechanisms. This study provides valuable insights into the effects of peripheral nerve blocks on thermoregulation and may contribute to the development of therapeutic strategies to managing perioperative hypothermia and enhancing pain management, especially in patients undergoing surgeries with high risks of thermoregulatory complications, such as on-pump surgery and laparoscopic surgery. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the association between circulating amino acids and central and peripheral body temperature in subjects with and without fibromyalgia syndrome (FMS). A total of 47 patients with FMS and 59 healthy subjects were included in the study. The concentration of amino acids was determined in serum samples using a fluorimeter coupled with a high-performance liquid chromatography system. An infrared thermography camera was used to estimate peripheral hand temperatures. The core temperature of the body was estimated using an infrared thermometer, which was applied to the axillary and tympanic areas. Correlations between several thermographic variables of the hands and tryptophan, methionine, 3-methylhistidine, histidine, glutamic acid, and tyrosine were identified exclusively within the FMS group. In contrast, correlations between aminoadipic acid and serine and thermographic variables were observed only in the healthy control group. The concentrations of asparagine and lysine correlated with thermographic variables in both groups. The essential amino acid leucine was found to correlate with axillary temperature in FMS patients. However, it should be noted that the observed associations between aminoadipic acid and tryptophan blood concentrations and axillary temperature were limited to the control group. Several correlations were identified between circulating amino acids and different body temperatures in both healthy controls and patients with FMS. However, the correlation pattern differs significantly between FMS patients and healthy controls. These findings suggest the possibility of a change in the function of several amino acids in the thermoregulatory process in patients with FMS. [ABSTRACT FROM AUTHOR]

Simple Summary: Many reptiles actively regulate their body temperature and during thermoregulation, they lose water from the body. The amount of body water lost in maintaining an adequate body temperature can vary from species to species. In this study, we compared the preferred body temperatures and the amount of water loss in males of two lacertid lizard species—the meadow lizard (Darevskia praticola) and the common wall lizard (Podarcis muralis)—that share the habitat at the western edge of the meadow lizard's distribution area. We hypothesized that the meadow lizard would exhibit higher water loss than the common wall lizard, as it generally prefers humid and forested places. However, the results showed that, at this locality, water loss is similar for both species, although the meadow lizard preferred lower ambient temperatures than the common wall lizard. We concluded that the meadow lizard has developed mechanisms to control water loss. Its preference for lower temperatures could be due to both historical factors and local adaptations. This information could help us to better understand how lizards cope with environmental changes and, more importantly, what we should do to prevent the species' decline in the wake of climate change. Many reptiles actively regulate their body temperature. During thermoregulation, they suffer evaporative water loss (EWL). Since evaporation increases with temperature, EWL could limit the activity of ectotherms when water is not available. In this study, we compared the preferred body temperatures (Tp) and EWL of two lacertid lizard species, Darevskia praticola and Podarcis muralis, at the western edge of D. praticola's range, where they live in syntopy. We hypothesized that D. praticola, a species that inhabits forested and humid environments, would have a higher EWL than the more widespread P. muralis. Our results show that D. praticola prefers lower temperatures (mean Tp = 28.1 °C) than P. muralis (mean Tp = 30.6 °C). Despite the differences in their thermal preferences, both species showed similar total EWL (2.76% for D. praticola and 2.67% for P. muralis), although their daily patterns of water loss differed. Our results suggest that D. praticola has developed mechanisms to control water loss and that its lower thermal preference may be due to both historical factors and local adaptations. These results contribute to the understanding of how environmental factors influence the physiology of lizards, which in turn has implications for predicting the effects of climate change on species distribution. [ABSTRACT FROM AUTHOR]

Heat stress is a problem that negatively affects animal welfare, health, and the productive efficiency of pigs. The objective of the study was to evaluate the effect of the trailer microclimate on some physiological, behavioral, and meat pH of fattening pigs during short‐duration journeys. Eight journeys (n = 216 pigs) of short duration (51.6 km and 1.5 h), originating from the same farm, were evaluated with a stocking density of 0.57 (±0.04) m2/100 kg (mean BW: 116.1 ± 7.52 kg). The thermal profile of the load (THI) was recorded in the four compartments of the truck. Upon arrival at the slaughterhouse, unloading was evaluated, and the percentage of nonambulatory pigs, mortality, and body temperature were recorded. Blood samples were obtained during exsanguination and the pH45 was measured. Overall, THI values recorded in all four compartments were below the threshold considered conducive to heat stress in pigs (23.9°C and THI ≤ 74). Serum concentrations of cortisol and the neutrophil/lymphocyte (N/L) ratio were above concentrations considered normal for the species (p < 0.05) and no significant differences were observed in average meat pH45 values according to the truck compartment (p > 0.05). The planning of transport in the morning hours and the consideration of the thermal environment of the truck is essential to reduce heat stress, economic losses, and negative effects on meat quality. [ABSTRACT FROM AUTHOR]

The commentary discusses the impact of climate change on epilepsy, focusing on insights from the 15th European Epilepsy Congress. It highlights the potential risks associated with rising global temperatures, such as increased seizure frequency and challenges in managing antiseizure medications. The commentary emphasizes the need for further research to understand the relationship between climate change and epilepsy, especially in vulnerable populations like individuals with developmental and epileptic encephalopathies. The authors call for more studies to develop prevention and mitigation strategies to protect individuals with epilepsy from the effects of climate change. [Extracted from the article]

The European Leaf-toed Gecko, Euleptes europaea, a rock-dwelling nocturnal gecko characteristic of Mediterranean Islands, is facing local extinctions and population decline at the margins of its range. Population monitoring through artificial retreat-sites (ARS) was implemented on French's Grand Rouveau and If islands to study the effects of management measures. We used Generalized Linear Models to identify: (i) the environmental variables (such as substrate, vegetation, and exposure to wind and sun) influencing the maximum number of individuals observed in ARS (studied in both islands); and (ii) the factors influencing ARS daily use (occupancy), including individual attributes such as age and weight, external temperature, and disturbance (Grand Rouveau only). The maximum number of geckos appeared to be determined by the thermal properties of ARS, as mediated by exposure to the dominant wind and sunlight, rather than by the structure of the habitat and nearby vegetation. An individual gecko's presence in an ARS was positively related to its presence in the same ARS on the previous day and negatively related to its age, the temperature of the previous night, and the number of days of disturbance. These results provide insights into the factors governing the selection and use of ARS by the European leaf-toed gecko and open perspectives on the use of ARS for the monitoring and conservation of this and other elusive terrestrial reptiles. [ABSTRACT FROM AUTHOR]

Background: Ambient temperature is one of the important factors affecting the survival of small mammals in the wild and different animals have different ways of regulating when face the same environmental temperature and different temperatures will also make the same species adjust the energy budget. Therefore, it is helpful to further understand the survival and adaptation patterns of different animals to study the different adjustment modes of animals in the same region in the face of high temperature environment. Methods: In the present study, three rodents, Apodemus chevrieri, Eothenomys miletus and E. olitor, were exposed to a high temperature (Ta) of 30℃ for 28 days. And then body mass, body temperature (Tb), resting metabolic rate (RMR) and thermal conductance (C) were measured at Ta from 5℃ to 35℃. Result: The results showed that Tb of all three mammals increased significantly with the increase of Ta. And thermal neutral zones (TNZ) among three animals were all 25℃-30℃. Moreover, RMR increased with the increase of Ta above the upper critical temperature Within the range of 30℃ to 35℃. C values in three mammals maintained stable within the Ta of 5℃-25℃, which increased with the increase of Ta above 25℃. All of the results suggested that three sympatric rodent species raised their Tb, narrowed their TNZ and changed C values to adapt to the high temperature. Moreover, change amplitudes of thermoregulation characteristics in E. olitor were small, indicating that E. olitor may have the strong adaptability under high temperature acclimation. [ABSTRACT FROM AUTHOR]

Animals are predicted to shrink and shape‐shift as the climate warms, declining in size, while their appendages lengthen. Determining which types of species are undergoing these morphological changes, and why, is critical to understanding species responses to global change, including potential adaptation to climate warming. We examine body size and bill length changes in 25 shorebird species using extensive field data (> 200,000 observations) collected over 46 years (1975–2021) by community scientists. We show widespread body size declines over time, and after short‐term exposure to warmer summers. Meanwhile, shorebird bills are lengthening over time but shorten after hot summers. Shrinking and shape‐shifting patterns are consistent across ecologically diverse shorebirds from tropical and temperate Australia, are more pronounced in smaller species and vary according to migration behaviour. These widespread morphological changes could be explained by multiple drivers, including adaptive and maladaptive responses to nutritional stress, or by thermal adaptation to climate warming. [ABSTRACT FROM AUTHOR]

Dogs, unlike humans, are equipped with a reduced number of sweat glands, which makes it difficult for them to dissipate heat, especially in conditions of intense activity that lead to a significant increase in body temperature. The study aims to investigate the metabolic differences between canine and human red blood cells (RBCs) and the hemoglobin (Hb) functionality focusing on their roles in heat dissipation. In detail, we evaluated the Band 3 protein (AE1) kinetic flux by observing that in canine red blood cells the anion exchange rate is higher than in humans (Rate Constant: 0.0438 min−1 and 0.012 min−1, respectively). Furthermore, we investigated the rate of ATP production and release to evaluate the possible variation of nucleotide concentration in the two species, observing a lower intracellular ATP concentration (101.80 μM and 297.90 μM) but a higher ATP release (3 μM and 2.65 μM) in canine RBCs compared to humans respectively. Subsequently, we evaluated the involvement of canine hemoglobin in heat dispersion; in detail, the ΔH= −5.15 Kcal/mol recorded in dog hemolysate at pH 7.5 shows an exothermic Hb-O2 bond that may be useful for further dispersing heat from the lungs. The peculiar oxygen-binding properties of dog Hb may also promote oxygen release in hyperventilation characterized by alkaline pH. [ABSTRACT FROM AUTHOR]

Basal metabolic rates (BMRs) increase with temperature and body mass. Environmental temperatures rapidly change in tropical mountains due to elevation (macro scale) and vegetation structure (micro scale). Thus, tropical mountains are good settings for testing the effects of temperature on BMRs. We measured the BMRs at four temperature ranges on six territorial and closely related species of Rubyspot damselflies (Hetaerina, Calopterygidae), which also share very similar behavior and morphology and are segregated by habitat and elevation across the Western Colombian Andes. We analyzed the effects of body mass, habitat, elevation, temperature, and sex on their BMRs, using a phylogenetic framework. We found that the main factors regulating their niche partition seemed to be environmental temperature, body size, and BMR. We found differences in their BMRs related to elevation when the temperatures were close to those experienced by the damselflies at their elevational range. As predicted, the larger species associated with colder habitats, forests, and highlands had higher BMRs. However, at high stressful temperatures, only the body mass was positively related to the BMR, showing that smaller individuals can keep their BMRs lower under high temperatures compared to bigger ones. Habitat use was not associated with changes in the BMR. Finally, phylogenetic reconstruction showed all species clustered in three clades. Each clade in the phylogenetic tree shares similar habitat preferences, pointing to a mixture of evolutionary history, thermal adaptations, and body mass differences as a possible explanation for the great diversity of these damselflies in a small area. Under the global warming scenario, we expect Rubyspots with smaller body sizes to be favored since they will tolerate higher temperatures, which would ultimately lead to populations with smaller body sizes overall, which could negatively affect their fitness. [ABSTRACT FROM AUTHOR]

Simple Summary: The tongues of vertebrates reflect their adaptations to various feeding strategies, the types of food they consume, and the environments they inhabit. In cetacean, the macro- and microanatomical aspects of the tongues of few species have been studied. Here, we analyzed, for the first time, the morphology of the tongues of two porpoise species (Spectacled and Burmeister's Porpoises; juvenile and adults), whose biology is little known. We describe a range of novel aspects related to ontogenetic morphological differences and document the finding of thermoregulatory structures and components of the immune system. Differences between juvenile and adult individuals of the same species, as well as between juveniles and adults of both species, may be related to their feeding types and/or geographical distribution. Additionally, we found a lingual vascular system, which has only been mentioned for baleen whales and the sperm whale (but never for smaller-toothed cetaceans), that may participate in the thermoregulation of these individuals. Both species have marginal papillae, but only in Burmeister's Porpoise were small taste buds, possibly vestigial, found. A better understanding of the biology of these two porpoise species will help to develop useful strategies that contribute to their protection in the near future. Vertebrates' tongues reflect part of their adaptations to diverse feeding strategies, the types of food items they eat, and the environments where they live. Our contribution was to analyze the macro- and microscopic morphology of the tongues of two porpoise species (Phocoena dioptrica and Phocoena spinipinnis; juveniles and adults), whose biology is little known. Macroscopic and microscopic studies (conventional histology, scanning electron microscopy, immunohistochemistry, and morphometry) were performed. Differences between juvenile and adult individuals of the same species, as well as between juveniles and adults of both species, were found, probably related to their feeding and/or geographical distribution. In addition, novel aspects related to ontogenetic morphological differences, thermoregulation, and immune system components were described. We found a lingual countercurrent vascular system (periarterial venous retia), only mentioned for mysticetes and Physeter macrocephalus (never for smaller odontocetes). In addition, we identified mechanoreceptors (lamellar corpuscles). Both species showed marginal papillae, but only in P. spinipinnis were small (probably vestigial) taste buds observed. Finally, lingual lymphoid aggregates were found. [ABSTRACT FROM AUTHOR]

Simple Summary: Japanese macaques, also known as snow monkeys, are known for their ability to huddle together in cold weather to stay warm. However, the size of these huddling groups can vary greatly across different regions, with exceptionally large clusters observed on Shodoshima Island compared to smaller groups in colder areas. This study used computer simulations to understand the factors influencing these huddling behaviours. By modelling individual decisions to join or leave a huddle based on temperature, group size, and other simple rules, we found that environmental conditions and local social dynamics play key roles in determining huddle size. Larger groups tend to form more clusters, but individual preferences and social tolerance also shape these behaviours. Our findings highlight how simple behaviours at the individual level can lead to complex group patterns. Understanding these dynamics not only helps us learn more about how animals survive in extreme conditions but also provides insights into the social structures and adaptability of Japanese macaques, which could inform conservation strategies and studies on animal behaviour. Huddling behaviour is observed across various mammalian and avian species. Huddling, a behaviour wherein animals maintain close physical contact with conspecifics for warmth and social bonding, is widely documented among species in cold environments as a crucial thermoregulatory mechanism. Interestingly, on Shodoshima, Japanese macaques form exceptionally large huddling clusters, often exceeding 50 individuals, a significant deviation from the smaller groups observed in other populations (Arashyama, Katsuyama, and Taksakiyama) and climates. This study aims to uncover the mechanisms behind the formation and size of these huddling clusters, proposing that such behaviours can be explained by simple probabilistic rules influenced by environmental conditions, the current cluster size, and individual decisions. Employing a computational model developed in Netlogo, we seek to demonstrate how emergent properties like the formation and dissolution of clusters arise from collective individual actions. We investigate whether the observed differences in huddling behaviour, particularly the larger cluster sizes on Shodoshima compared to those in colder habitats, reflect variations in social tolerance and cohesion. The model incorporates factors such as environmental temperature, cluster size, and individual decision-making, offering insights into the adaptability of social behaviours under environmental pressures. The findings suggest that temperature plays a crucial role in influencing huddling behaviour, with larger clusters forming in colder climates as individuals seek warmth. However, the study also highlights the importance of joining and leaving a cluster in terms of probability in the dynamics of huddling behaviour. We discussed the large clusters on Shodoshima as a result of a combination of environmental factors and a unique social tolerance and cohesion among the macaques. This study contributes to our understanding of complex social phenomena through the lens of self-organisation, illustrating how simple local interactions can give rise to intricate social structures and behaviours. [ABSTRACT FROM AUTHOR]

Ischemic preconditioning (IPC) is a strategy that may enhances endurance performance in thermoneutral environments. Exercising in the heat increases thermoregulatory and cardiovascular strain, decreasing endurance performance. The current study aimed to determine whether IPC administration improves endurance performance in the heat. In a randomized crossover design, 12 healthy subjects (VO2max: 54.4 ± 8.1 mL⋅kg-1⋅min-1) underwent either IPC administration (220 mmHg) or a sham treatment (20 mmHg), then completed a moderate-intensity 6-min running (EX1) and a high-intensity time-to-exhaustion running test (EX2) in a hot environment (35 °C, 50 % RH). Cardiac function, oxygen consumption (VO2), and core body temperature (TCORE) were measured. During EX2, IPC administration increased the total running time in the heat compared to the sham treatment (IPC: 416.4 ± 61.9 vs. sham 389.3 ± 40.7 s, P = 0.027). IPC administration also increased stroke volume (IPC: 150.4 ± 17.5 vs. sham: 128.2 ± 11.6 ml, P = 0.008) and cardiac output (IPC: 27.4 ± 1.7 vs. sham: 25.1 ± 2.2 ml⋅min-1, P = 0.007) during 100% isotime of EX2. End-exercise VO2 (IPC: 3.72 ± 0.85 vs. sham: 3.54 ± 0.87 L⋅min-1, P = 0.017) and slow phase amplitude (IPC: 0.57 ± 0.17 vs. sham: 0.72 ± 0.22 L⋅min-1, P = 0.016) were improved. When compared with the baseline period, an increase in TCORE was less in the IPC condition during EX1 (IPC: 0.18 ± 0.06 vs. sham: 0.22 ± 0.08 °C, P = 0.005) and EX2 (IPC: 0.87 ± 0.10 vs. sham: 1.03 ± 0.10 °C, P < 0.001). IPC improves high-intensity endurance performance in the heat by 6.9 %. This performance benefit could be associated with improved cardiac and thermoregulatory function engendered by IPC administration. [ABSTRACT FROM AUTHOR]

The rapid advancements in advanced textile technology and artificial intelligence have laid a robust technological foundation for the continuous innovation of smart and functional clothing products meeting the diverse dressing needs in everyday life work and study. In particular temperature regulating clothing designed for human body temperature modulation plays a crucial role in industries exposed to extreme working conditions such as firefighting and rescue construction operations border patrol and specialized emergency response. As the market demand for temperature regulating clothing grows the volume of scholarly research in this field has also increased. However most studies focus on specific areas such as cooling garments heating garment or textile materials and rely primarily on literature reviews for analyzing the current status and future prospects. There is a notable lack of visual analysis in the field of temperature regulating clothing. With the rise of bibliometric methods in the textile and apparel sector more scholars are now using visualization tools to analyze trends in their research areas. Therefore to explore the current research status and development trends in the field of temperature-regulating clothing this paper systematically reviews academic literature in both Chinese and English using bibliometric analysis and literature review methods from a multidimensional perspective. In order to ensure the timeliness accuracy and authority of the data with the help of VOSviewer and CiteSpace a multidimensional metrological and visual analysis of 1 384 Chinese and English documents closely related to the field of temperature regulating clothing in the CNKI and WOS core collection databases from January 1 2000 to March 1 2024 is made in this paper. This study primarily conducts a knowledge mapping analysis and descriptive statistical analysis of key aspects related to temperature regulating clothing including the annual publication volume contributing authors publishing institutions countries/ regions keyword co-occurrence and clustering and keyword timelines. Using bibliometric and literature review methods the research systematically examines the current progress and development trends in temperature regulating clothing from a visual analysis perspective. The findings indicate that the number of Chinese and English publications on temperature regulating clothing showed steady growth before 2021. However with continuous advancements in international temperature regulating materials and cutting-edge technologies the field has attracted more attention from international scholars leading to a significant gap in the number of English publications compared to Chinese ones in recent years. China and the United States dominate the field of temperature regulating clothing with Donghua University and The Hong Kong Polytechnic University being the leading institutions in terms of publication volume. These two institutions also have the closest collaborative relationship in this field. Scholars such as Li Jun Wang Faming Psikuta A Rossi Rene M and Fan Jintu are identified as core researchers in the area. Since 2000 the research on temperature regulating clothing at home and abroad can be roughly divided into three stages namely the initial stage 2000 2006 the exploration and development stage 2007 2016 and the diversified development stage 2017 to present . The research on temperature regulating clothing at home and abroad is mainly used in the fields of fire rescue medical protection coal mine and tunnel construction and other industries in extreme working environment. At present more attention is paid to the exploration of performance optimization of temperature regulating clothing from human physiological reaction data and gradually focus on the wearer. Through the comparative analysis of keyword clustering and high-frequency keywords in Chinese and English literature it is found that there is a high degree of overlap in the structure and content of research topics at home and abroad. The research hotspots in temperature-regulating clothing can be summarized into three main themes the first is the study of temperature regulation methods the second is the performance evaluation of temperature-regulating clothing and the third is the interaction between temperature-regulating clothing and individual physiological indicators. In summary this article provides a systematic review of temperature regulating clothing research both domestically and internationally and outlines the future research directions in the field of temperature regulating clothing. Firstly it is necessary to enhance the research and development of lightweight high-efficiency exogenous equipment and new thermoregulation materials. Secondly it is necessary to establish and improve industry standards and production specifications related to thermoregulation garments. Thirdly it is necessary to optimize experimental testing programs for thermoregulation garments and develop a multi-dimensional performance evaluation system. Finally it is necessary to develop multifunctional and integrated intelligent thermoregulation garments based on digital-intelligent synergism. The study aims to facilitate the further development of temperature regulating clothing so as to provide valuable insights and recommendations for future advancements towards enhanced digital intelligence flexibility comfort and functional integration in temperature-regulating garments. [ABSTRACT FROM AUTHOR]

Colonisation of novel habitats are important events in evolution, but the factors that initially prompt such ecological transitions are often unknown. The invasion of land by fish is an extreme habitat transition that offers an opportunity to empirically investigate the causes of major ecological transitions.The intertidal ecotone—and rock pools in particular—have been an important staging ground for transitions onto land. Classic hypotheses focus on the adverse abiotic conditions of rock pools at low tide as the instigator of fish voluntarily stranding themselves out of water, which can then lead to the evolution of an amphibious lifestyle. To test these hypotheses, we studied the abiotic conditions of 54 rock pools on the island of Guam where there are various species of aquatic, amphibious and terrestrial blenny fishes.We found little support for the expected deterioration of abiotic conditions in standing pools at low tide (salinity, pH and oxygen), and fish were not seen to be excluded from those pools that were found to exhibit poor abiotic conditions (temperature, salinity and pH). Hypoxia was the only factor that might account for the absence of blennies from certain rock pools.Next, we experimentally measured oxygen depletion by an aquatic, mildly amphibious and highly amphibious species of blenny found on Guam in a simulated rockpool to infer the proportion of rock pools at low tide outside the tolerable range of blennies. Rock pools were found to have oxygen levels within the requirements of most blennies and those of other marine fishes reported in the literature.We conclude that the abiotic environment of rock pools alone was unlikely to have instigated the evolution of amphibious behaviour in blennies, at least on Guam. Instead, the broad range of abiotic conditions experienced in rock pools suggests these conditions could have primed amphibious blennies to better endure the novel conditions on land. Any ecotone typified by fluctuations or gradients in abiotic conditions is likely a key transitional environment for the invasion of novel habitats and, as such, are an important location for adaptive evolution and species diversification. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

We compared two methods of partitional calorimetry to calculate heat storage and heat debt during cold air (0°C) exposure causing mild core cooling. Twelve participants performed a 5 min baseline in thermoneutral conditions (∼22.0°C, ∼50% relative humidity) followed by cold air exposure (∼0°C) until rectal temperature was reduced by ∆−0.5°C. Partitional calorimetry was used to calculate avenues of heat exchange (radiative, convective, and evaporative), heat storage, and heat debt continuously throughout cold exposure. We compared deriving these variables using prediction equations based on environmental and participant characteristics (PCALEquation Method) versus using measurement tools such as humidity sensors and heat flux discs (PCALHeat Flux Method). There were significant differences between methods (all p ≤ 0.001) for determining heat exchange, heat storage, and heat debt. At ∆−0.5°C, PCALHeat Flux Method had greater levels of radiative and convective heat exchange (PCALHeat Flux Method: −143.0 ± 16.8 W∙m2 vs PCALEquation Method: −123.0 ± 12.9 W∙m2, p ≤ 0.001), evaporative heat exchange (PCALHeat Flux Method: −9.0 ± 1.7 W∙m2 vs PCALEquation Method: −4.1 ± 0.0 W∙m2, p ≤ 0.001), heat storage (PCALHeat Flux Method: −15.0 ± 31.0 W∙m2 vs PCALEquation Method: +6.0 ± 25.9 W∙m2, p = 0.020), and heat debt (PCALHeat Flux Method: −692.0 ± 315.0 kJ vs PCALEquation Method: −422.0 ± 136.0 kJ, p ≤ 0.001). Overall, this study found the largest discrepancies between the two methods were when the environmental conditions and skin temperature were in high flux, as well as when core temperature was reduced by ∆−0.5°C. The use of PCALHeat Flux Method may be more advantageous to use in the cold to provide a higher resolution measurement of cold strain. [ABSTRACT FROM AUTHOR]

Wet clothing is less insulative than dry clothing and consequently increases heat loss in cold air. Tactical necessity can render removal of wet clothing impossible and/or require Warfighters to remain static to avoid detection, limiting heat production and posing a threat of hypothermia (core temperature <35 °C). This study aimed to characterize body temperatures and evaluate hypothermia risk while statically exposed to 5 °C air wearing three wet military uniforms. Further, low-speed loaded walking was evaluated as a strategy to raise end-static temperatures. Twelve adults (11 M, 1 F) randomly completed three wet-cold trials wearing either the Improved Hot Weather Combat Uniform (IHWCU), Army Combat Uniform (ACU), or ACU with silk-weight base layer (ACU+). Each trial involved 180 min of cold air (5.3 ± 0.3 °C, 0.8 m·s−1) exposure after a clothed 2 min head-out immersion (34.0 ± 0.2 °C). Volunteers were static for 60 min followed by 120 min of walking with a rucksack. Rectal temperature (Tre) area under the curve did not differ among the three wet uniforms when static (p = 0.431) with Tre increasing, rather than decreasing, across the 60 min (IHWCU: +0.26 ± 0.19 °C, ACU: +0.37 ± 0.21 °C, ACU+: +0.36 ± 0.20 °C). Hypothermia risk with 60 min static wet-cold exposure therefore appears minimal, regardless of the military uniform worn, in an otherwise low stress cohort. End-static finger temperatures (IHWCU: 9.48 ± 2.30 °C, ACU: 9.99 ± 1.82 °C, ACU+: 9.27 ± 1.66 °C, p > 0.999) were reduced by ∼20–23 °C posing a considerable dexterity concern. Heat production of ∼210 W·m2 appeared sufficient to begin to reverse negative cumulative heat storage and initiate slight elevations of rectal and peripheral temperatures, although finger temperatures increased <2 °C after 120 min. ClinicalTrials.gov ID: NCT05409937. [ABSTRACT FROM AUTHOR]

While foot immersion and neck cooling have been recommended for protecting heat-vulnerable groups, recent evidence does not support their efficacy for mitigating increases in physiological heat strain in older adults. However, their influence on self-reported environmental symptoms and mood-state remains unclear. Seventeen older adults (nine females, median [interquartile range] age: 72 [69–74]) completed three randomized heat exposures (6-h; 38°C, 35% relative humidity) with no cooling (control), foot immersion to mid-calf in 20°C water for the final 40-min of each hour (foot immersion), or foot immersion with a wet towel (20°C) around the neck (foot immersion with neck cooling). Core temperature, skin temperature, and heart rate areas under the curve (AUC) were assessed as indicators of cumulative physiological strain. Environmental symptom scores (68-item environmental symptoms questionnaire) and mood disturbance (40-item profile of mood states questionnaire) were evaluated at end-heating (adjusted for pre-exposure). Core temperature AUC was not different between conditions (p = 0.418). However, the skin temperature and heart rate AUCs were 11.8°C · h [95% confidence interval: 8.1, 15.5] and 12.5 bpm · h [0.1, 24.8] lower for foot immersion and 16.6°C · h [12.9, 20.3] and 19.6 bpm · h [7.2, 32.0] lower for foot immersion with neck cooling compared to control (p ≤ 0.032). Environmental symptom scores were 0.8-fold [0.6, 1.0] lower for both foot immersion with and without neck cooling, compared to control (both p = 0.036). Mood disturbance was not different between conditions (both p ≥ 0.275). Foot immersion with and without neck cooling reduces self-reported environmental symptoms in older adults despite having little effect on physiological heat strain. [ABSTRACT FROM AUTHOR]

The International Olympic Committee recently introduced a consensus statement on recommendations for outdoor sports in the heat. However, indoor sports such as fencing whereby athletes are required to wear full body protective clothing when competing have received no recommendations. Such scenarios could cause high thermoregulatory demands particularly as competition progresses into latter rounds (direct elimination; DE). Therefore, the aim of this study was to determine the thermoregulatory responses of épée fencing across different phases of competition (Poule and DE). Seven well-trained fencers competed in a simulated competition comprising of seven Poule and seven DE fights. Gastrointestinal temperature (Tgast), skin temperature (Tskin), mask temperature (Tmask), heart rate (HR), thermal sensation, differentiated ratings of perceived exertion (RPE), and movement characteristics were collected for all fights. There was a moderate thermoregulatory demand during Poule rounds shown by post-fight Tgast (38.1 ± 0.4°C), Tskin (34.4 ± 0.7°C), and thermal sensation ratings (6 ± 1). A greater thermoregulatory and perceptual demand observed during DE rounds evidenced by Tgast (38.7 ± 0.3°C post fight), Tskin (35.1 ± 0.7°C), thermal sensation (7 ± 1), increases in Tmask across DE rounds (~1.1°C), and RPE (~15). Furthermore, a significant (p < 0.05) reduction in distance covered from DE 1 to DE 7 suggests a thermoregulatory based impact on performance. This is the first study demonstrating the thermoregulatory demands of épée fencing, highlighting the need to develop heat exertion guidelines within fencing. [ABSTRACT FROM AUTHOR]

Wet bulb globe temperature (WBGT) is a commonly used measure to predict heat strain in workers. Different combinations of environmental conditions can create equivalent WBGT, yet it remains unknown whether biophysical, physiological, and perceptual responses vary when working in different but equivalent hot conditions. The purpose of the study was to compare body heat storage and physiological and perceptual strain during walking in hot-dry and warm-wet conditions of the same WBGT. Twelve subjects (age: 22 ± 2 y) walked for 90 min at 60% maximum heart rate in a 27.8°C WBGT environment of hot-dry (HD: 40°C, 19% relative humidity) or warm-wet (WW: 30°C, 77% relative humidity) conditions. Partitional calorimetry was used to estimate heat storage. Core temperature at 90 min (HD: 38.5 ± 0.5°C; WW: 38.4 ± 0.3°C, p = 0.244) and cumulative heat storage (HD: 115 ± 531 Kj; WW: 333 ± 269 Kj, p = 0.242) were not different. At 90 min, heart rate was not different (HD: 160 ± 19 bpm; WW: 154 ± 15 bpm, p = 0.149) but skin temperature (HD: 36.6 ± 0.9°C; WW: 34.7 ± 0.6°C, p < 0.001), thirst (HD: 6.8 a.u.; WW: 5.3 a.u. p = 0.043), and sweat rate (HD: 15.1 ± 4.4 g·min−1; WW: 10.0 ± 4.1 g·min−1, p < 0.001) were greater in HD compared to WW. Hot environments of equivalent 27.8°C WBGT created equivalent core temperature despite differences in physiological strain during exercise, including earlier onset of cardiovascular strain, greater sweat rate, and higher skin temperature compared to a WW environment. ClinicalTrials.gov ID NCT04624919. [ABSTRACT FROM AUTHOR]