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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]

Heat waves are becoming increasingly common due to climate change, making it crucial to identify and understand the capacities for insect pollinators, such as honey bees, to avoid overheating. We examined the effects of hot, dry air temperatures on the physiological and behavioral mechanisms that honey bees use to fly when carrying nectar loads, to assess how foraging is limited by overheating or desiccation. We found that flight muscle temperatures increased linearly with load mass at air temperatures of 20 or 30 °C, but, remarkably, there was no change with increasing nectar loads at an air temperature of 40 °C. Flying, nectar-loaded bees were able to avoid overheating at 40 °C by reducing their flight metabolic rates and increasing evaporative cooling. At high body temperatures, bees apparently increase flight efficiency by lowering their wingbeat frequency and increasing stroke amplitude to compensate, reducing the need for evaporative cooling. However, even with reductions in metabolic heat production, desiccation likely limits foraging at temperatures well below bees critical thermal maxima in hot, dry conditions.

An ectotherm's performance and physiological function are strongly tied to environmental temperature, and many ectotherms thermoregulate behaviourally to reach optimum body temperatures. Tropical ectotherms are already living in environments matching their thermal tolerance range and may be expected to conform to environmental temperatures. We tracked the body temperatures (Tb) of 163 estuarine crocodiles across 13 years and compared Tb of 39 crocodiles to water temperature gathered using fish-borne sensors (Tw) across 3 years (2015–2018). While Tb largely conformed closely to Tw, we found inter- and intra-individual differences in relative body temperature (Tb–Tw) that depended on sex and body size as well as the time of day and year. Deviations from Tw, especially during the warm parts of the year, suggest that thermoregulatory behaviour was taking place: we found patterns of warming and cooling events that seemed to mediate this variation in Tb. Thermoregulatory behaviour was observed most frequently in larger individuals, with warming events common during winter and cooling events common during summer. By observing free-ranging animals across multiple years, we found that estuarine crocodiles show yearly patterns of active cooling and warming behaviours that modify their body temperature, highlighting their resilience in the face of recent climate warming. Our work also provides the first evidence for thermal type in large-bodied reptiles. [ABSTRACT FROM AUTHOR]

Heat stress poses a substantial challenge to poultry production worldwide, highlighting the urgent need for effective management strategies. This study investigated the efficacy of probiotics (Saccharomyces cerevisiae) and ascorbic acid as antistress agents using cloacal and body surface temperatures (CT and BST) as heat stress biomarkers in broiler chickens. A total of 56 broiler chicks were used for the experiment and were divided into four distinct groups: control, probiotics (1 g/kg of feed), ascorbic acid (200 mg/kg of feed) and the combination of probiotics and ascorbic acid (1 g/kg and 200 mg/kg of feed, respectively). The study lasted 35 days; measurements were taken for ambient temperature (AT), CT, and BST. The ambient temperature in the pens consistently exceeded the thermoneutral zone (TNZ) established for broiler chickens. The CT values for broiler chickens in the probiotic group were significantly lower (p < 0.05) compared to the control group. Additionally, the BST values in the probiotic and probiotic + ascorbic acid groups were significantly lower (p < 0.05) than those in the control group. The findings suggest that incorporating probiotics, with or without ascorbic acid, can effectively reduce CT and BST values in broiler chickens thereby, enhancing thermoregulation when compared to the control group. This implies that using probiotics in poultry diets may enhance health and growth performance, potentially leading to better feed efficiency and reduced reliance on antibiotics. Implementing these dietary strategies could improve the productivity and welfare of broiler chickens in commercial settings. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the effect of using naturally shaded pastures on scrotal thermoregulatory capacity, testicular echotexture, and sperm morphology of Nelore (Bos indicus) and Canchim (5/8 Bos taurus x 3/8 Bos indicus) bulls in a tropical climate region. Sixty-four adult Nelore and Canchim bulls were used, equally allocated in Full Sun (FS, n = 32) or Crop-Livestock-Forestry (CLF, n = 32) pasture systems. During five consecutive climate seasons, the bulls underwent monthly breeding soundness evaluations and the biometeorological variables in the systems were continuously monitored. Microclimate was significantly different between systems. CLF system had lower BGHI than FS throughout the experimental period. No triple interaction (Season x Breed x Treatment, P > 0.05) was observed for any of the variables. Animals in CLF showed lower body temperature in Summer (FS:39.41 ± 0.05 vs. CLF:39.30 ± 0.05 °C; P = 0.005) and in Autumn (FS:39.54 ± 0.05 vs. CLF:39.35 ± 0.05 °C; P = 0.005). Access to shading did not determine differences in the evolution of scrotal biometry, temperatures, and scrotal thermal gradients (P > 0.05). Regardless of breed, animals in CLF showed greater right testicular volume (FS:247.5 ± 5.7 vs. CLF:259.0 ± 5.7 cm³; P < 0.05), more suitable parenchyma echotexture, and fewer microlithiasis spots in the Spring and Summer. Testosterone concentration was higher in FS (FS:2.6 ± 0.2 vs. CLF:2.1 ± 0.2 ng/mL; P = 0.035). Canchim bulls presented higher total sperm defects during the Autumn and Winter (P = 0.010), but the total defects levels for Canchim and Nelore bulls were in normal range for adult bulls. Thus, the natural shade in CLF system was effective in improving the microclimate of pastures and minimizing adverse environmental effects on some reproductive features of interest in beef cattle. [ABSTRACT FROM AUTHOR]

In this study, we conducted a literature review to deepen our understanding of the sweating response of the thermoregulatory system, focusing on the influence of individual characteristics and local body functions. Among the factors related to individual characteristics, improvement in aerobic fitness had a positive effect on the sweating response, whereas aging exerted an inhibitory effect. Short-term artificial acclimation and seasonal heat acclimatization promoted sweating, whereas long-term geographical acclimatization suppressed sweating. Male exhibited higher sweat rates than female when the metabolic heat production was high. Individuals with smaller surface area-to-mass ratios tended to have higher sweat rates than those with larger ratios. Regarding local body functions, sweat distribution in the resting state showed high regional sweat rates in the lower limbs and torso, with higher values in the lower limbs when in the supine position and higher values in the torso when in the seated position. During exercise, the regional sweat rates was high in the torso, whereas the limbs exhibited relatively low sweat rates. These differences in sweat distribution stem from the thermoregulatory potential of each body region, which aims to efficiently regulate body temperature. Local effects have only been examined in the thigh and forearm, with temperature coefficient Q10 ranging from 2 to 5. Only the forehead showed significantly high thermosensitivity among all body regions. [ABSTRACT FROM AUTHOR]

Purpose: The current study investigated whether sustained mild dehydration affects thermoregulatory function and cognitive performance during prolonged exercise. Methods: Twelve young adults performed a test consisting of three sets of 20-min exercise with 2-min intervals under euhydrated (control, CON) and mildly dehydrated conditions (MDEH) at an ambient temperature of 30 °C and 60% relative humidity. MDEH was established by restricting water intake for 24 h, resulting in urine specific gravity of ≥ 1.020. Heart rate (HR), mean arterial blood pressure (MAP), skin blood flow (SkBF), sweat rate (SR) on the chest and forearm, and ear canal and mean skin surface temperatures (Tear and mean Tskin, respectively) were continuously recorded. For each exercise set, thermal and humid sensations and thermal discomfort were assessed using visual analog scales (VAS), and the rating of perceived exertion (RPE) was estimated. Cognitive performance on the Go/No-Go (easy) and incongruent Stroop (difficult) tasks was assessed before and after the test. Results: No differences were observed in HR, MAP, SkBF, SR, Tear, and mean Tskin between the CON and MDEH. Thermal and humidity sensations, thermal discomfort, and RPE were higher in MDEH than in CON. Moreover, response time to the Stroop task was prolonged in MDEH. Conclusion: These findings suggest that sustained mild dehydration does not affect autonomic thermoregulation during exercise. Augmented thermal perception and perceived exertion, which are necessary for behavioral thermoregulation, were noted; however, cognitive function may be attenuated under MDEH. [ABSTRACT FROM AUTHOR]

Monitoring environmental conditions over time is essential for understanding how species regulate those conditions to satisfy their physiological needs. Variation in ultraviolet (UV) light exposure, for instance, is crucial for numerous taxa, influencing behaviour as well as essential physiological processes like vitamin D3 synthesis. Yet, despite these considerations, no commercially available data loggers exist to record UV exposures over time, preventing inquiry into this important but neglected fitness demand.To overcome this challenge, I designed the first UV data logger, custom built on the open‐source Arduino platform. This device logs UV exposures (in voltage or converted to UV index) and date‐time information for each UV reading, at user‐defined intervals. The integration of a low‐power timer into the assembly, and its weather‐resistant housing, enables long‐term use (at least several months). The cost of one device (including housing) is under £45/$55 USD.Calibration and performance tests reveal that this device is reliable under various weather conditions and produces accurate UV readings under both artificial lighting and sunlight. Both the device and its customised housing can be easily replicated and expanded upon (e.g. inclusion of additional sensors).Overall, this device represents a crucial first step in our ability to better characterise UV exposure patterns in habitats for physiological ecology studies. Exposure to UV light is adaptive for many types of organisms, both in the wild and in captivity (e.g. zoos and private hobbyists), and so I expect a broad array of scientific and public users alike to benefit from using this device. [ABSTRACT FROM AUTHOR]

In a year-long research study, we delved into the thermoregulation and performance of twenty-one honey bee colonies situated in three distinct landscape settings: 1- Urban, 2- Agricultural (AG), and 3- Non-agricultural (Non-AG) environments. All colonies, consistent in size, were equipped with sensors designed to record inner hive temperature and humidity. Additionally, colonies were placed on precision electronic scales for weight monitoring. Varroa mite infestations were documented at seven different time points throughout the experiment. Colonies were genetically analyzed for subspecies and haplotype identification using the in silico DraI mtDNA COI-COII test. Our results unveiled an overall significant (p < 0.001) weight gain (5.76 kg) in colonies located within the urban setting, in stark contrast to both AG and Non-AG locations. Notably, colonies situated in the natural refuge center (Non-AG) experienced a weight loss of −0.05 kg, signaling a lack of sustainable forage resources in such a setting. Similarly, the inner hive temperature was significantly (p < 0.001) higher in the urban area (33.65 °C) with a significantly lower relative humidity (61.2%) compared to both other locations. Among the locations, the temperature variable displayed the strongest significant correlation (p < 0.001) with a positive correlation coefficient (r = 0.95). Two distinct mtDNA haplotypes were identified: C1 and C2j, characterizing the ligustica and carnica maternal origin, respectively. These haplotypes consistently demonstrated significant differences in their thermoregulation and weight gain, irrespective of the landscape compositions. The C1 haplotype displayed significantly higher weight gain alongside lower inner hive temperature and humidity levels compared to the C2j haplotype. No differences in mite infestation were observed between the various locations or haplotypes. Our data underscores the substantial impact of landscape composition on honey bee performance. It also unveils significant variations in thermoregulation and adaptation between haplotypes, shedding light on the multifaceted relationship between environmental factors, genetics, and bee colony dynamics. [ABSTRACT FROM AUTHOR]

Purpose: Maintaining normothermia during the perioperative period is crucial for preventing complications, such as surgical site infections, prolonged hospital stays, and adverse cardiovascular events. This study aimed to elucidate methods of perioperative temperature management by integrating Western and traditional Chinese medicine (TCM) approaches. By combining advanced techniques of Western medicine with holistic and preventative practices of TCM, we aimed to provide a comprehensive strategy for effective perioperative thermal regulation. Methods: And a comprehensive literature review was conducted to analyze the causes of perioperative hypothermia and methods of perioperative temperature management from both Western and traditional Chinese medicine (TCM) perspectives. Special emphasis was placed on evaluating the underlying factors contributing to perioperative hypothermia, as well as the effectiveness, selection criteria, indications, contraindications, adverse reactions, and potential complications associated with various temperature management techniques. Results: Effective prevention and management strategies include preoperative risk assessment, physical warming measures, environmental temperature control, pharmacological interventions, perioperative temperature monitoring, comprehensive warming protocols, and postoperative warming and monitoring. Integrating traditional Chinese medicine provides additional methods to enhance overall effectiveness and patient outcomes. By combining these approaches, healthcare providers can significantly reduce the incidence of inadvertent perioperative hypothermia (IPH) and its associated complications, improving patient safety and recovery. Conclusion: For IPH, a complex and challenging medical condition, both traditional Chinese medicine and Western medicine have established their own theoretical bases and developed corresponding prevention and treatment methods. However, it is important to note that although each of these methods has unique value and potential, they also have specific indications and unavoidable limitations. Therefore, by integrating and combining the complementary strengths and resources of traditional Chinese medicine and Western medicine, we can achieve a more comprehensive and effective prevention of IPH, ultimately improving the health and well-being of those affected. [ABSTRACT FROM AUTHOR]

Introduction: Indoor cycling at home has grown rapidly in recent years facilitated by advances in technology and gamification. However, there is limited data on individual's training practices when cycling indoors. Methods: Using a single-time point, cross-sectional questionnaire, we gathered information on equipment, environmental considerations, training practices and nutrition during indoor cycling. Results: Following 492 responses, external variables (weather; 88.4%, lack of daylight; 56.3%), time efficiency (81.9%) and general fitness (70.9%) were most frequently cited as reasons to engage in indoor cycling. "Smart" turbo trainers linked to a mixed-reality cycling software were most frequently reported in equipment set-up. 78% of participants attempted to control temperature with 96% of these participants using at least 1 fan to control airflow. The volume of indoor training differed between seasons (winter: 6h10 ± 3 h 30, summer 2h52 ± 2h57, p < 0.001), and structured (61.9%) and unstructured work-outs (64.7%) were completed more than once a week with fewer participants engaging in competitive/racing events (20.9%). 98% percent of participants consumed fluids with an average fluid intake of 0.74 ± 0.28 L/h. Dependent on type of work-out, participants reported less planning of carbohydrate and protein intake during short-duration work-outs (~40%-60%) relative to longer-duration work-outs (~56%-80%). Caffeine use was the most frequently reported ergogenic aid. Conclusion: Together we report indoor cycling practices with respect to training equipment, considerations of environmental and nutritional strategies and training habits. Our findings could be used to support the development of future research and indoor training guidelines. [ABSTRACT FROM AUTHOR]

Atlantic salmon Salmo salar typically enter fresh water several months prior to spawning and just as pools can provide areas of refuge in river systems, lakes may also provide important refuge habitat during the spawning migration. Using acoustic telemetry we examined the spatial and temporal movements of wild and a ranched strain of Atlantic salmon in a freshwater lake where the main spawning areas were located upstream of the lake. Over the study period (2011–2014), returning adult wild salmon spent an average of 228 days in fresh water and 90% of that time in the lake. On entering the lake, most wild salmon moved quickly to the northern part of the lake, close to the main inflow, spending an average 76% of the time in this location. The average number of days wild fish were absent from the lake during the main spawning period varied between years, ranging from 10 to 26 days for females and 32 to 35 days for males. Seventy four per cent (17/23) of salmon spawners returned to the lake and two salmon subsequently died in the lake post‐spawning. Atypically, two salmon were resident in the lake for the whole period in 2013/14. During the study, wild salmon were detected at depths within the top 5 m for 73% of the time. Median depths post‐spawning were greater than in the pre‐spawning period, when salmon were found to spend extensive periods at depths in excess of 10 m. In July 2013, when the lake was stratified, thermal regulation behaviour was observed in wild salmon, whereby salmon moved to cooler deeper water when water temperatures at 1 m exceeded 20°C. In contrast to wild salmon, the majority of ranch salmon returned to the traps downstream of the lake prior to the spawning period, which would be expected as they were released as smolts below the freshwater lake. Ranch fish spent an average 80% of the time in the vicinity of receivers in the south of the lake and an average 98% of the time within the top 5 m. However, two ranch females were resident in the lake until the following spring and one ranch female moved upstream into the river during the spawning period. Clearly, in this catchment the lake provides an important habitat for migrating adult salmon. In the context of climate change, where thermal and hydrological regimes in rivers are expected to change in response to changes in air temperature and precipitation patterns, the availability of deep lakes that stratify in the summer and cool water refuges in river systems is likely to play a key role in the sustenance and conservation of salmonid species. Information about the migration patterns of Atlantic salmon in undisturbed freshwater systems may also assist in resolving issues associated with fish passage in impacted rivers and inform management decisions. [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]

Introduction: Diving in SCUBA modality modifies human physiology in many ways. These modifications have been studied since Paul Bert in a seminal work. This area of research is very sensible to technological development. At now, it is possible to record heart rate (HR) continuously while diving. The study of HR changes in SCUBA diving at different depths in a constant temperature of thermal water is the objective of the present paper. Methods: 18 healthy subjects were enrolled and HR was recorded while SCUBA diving in thermal water at a constant temperature of 33.6°C in the deepest Italian pool at Montegrotto (Padova, Italy). Three depths were investigated: -20, -30 and -40 meters. The HR has been recorded with a Galileo SOL diving computer. The dive was subdivided into three phases: descent (DSC), steady on depth (STD), post-dive (RSF), and average HR was evaluated in each phase. Moreover, considering the DSC and STD time duration, a statistical linear regression of HR and relative parameters, intercept and slope, were here assessed. Results: In STD phase, HR slope obtained by regression decreased with depth. A significant difference was found between the slope during STD at -20 vs. -40 m (p = 0.05). Discussion: Present results emphasized different HR physiological adjustments among diving phases. Firstly, during the DSC, a rapid HR decrease is recognized as probably due to a vagal response; secondly, at STD, the inward blood redistribution requires another physiological adjustment. This latter is depth-dependent because of a reduction of cardiac variability. Present data highlight the important cardiac stress need to counteract the diving activity. [ABSTRACT FROM AUTHOR]

In order to enhance the application of thermoregulated materials, magnetic phase change microcapsules were prepared using a self-assembly method. Paraffin wax was chosen for its fine thermoregulation properties as the core material, while Fe3O4 nanoparticles doped in calcium carbonate served as the hybrid shell material. The microcapsules were then blended with sodium alginate and processed into seaweed fibers through wet spinning. The microstructure, thermal, and magnetic properties of the microcapsules were analyzed using scanning electron microscopy, energy dispersive X-ray spectroscopy, a laser particle size analyzer, an X-ray diffractometer, a differential scanning calorimeter, a thermogravimetric analyzer, and a vibrating sample magnetometer. The thermoregulation of the fibers was evaluated using a thermal infrared imager. The results indicated that the microcapsules had a uniform size distribution and good thermal properties. When the mass fraction of Fe3O4 nanoparticles was 8%, the microcapsules exhibited a saturation magnetization of 2.44 emu/g and an enthalpy value of 94.25 J/g, indicating effective phase change and magnetic properties. Furthermore, the thermoregulated seaweed fibers showed a high enthalpy value of 19.8 J/g with fine shape, offering potential for developing multifunctional fiber products. [ABSTRACT FROM AUTHOR]

Context: The coat is the first defense layer protecting animals from direct sunlight, influencing radiant-heat absorption and loss. Dark coat colour may increase animal heat impact because of higher absorption of solar radiation. Aims: We investigated the impact of pigmentation intensity on the heads of animals and their thermal responses to solar radiation. Furthermore, we compared the thermal responses between dark and light brown-coloured animals, to determine whether the duration of sun and shade exposure (3 h each) is sufficient to differentiate the heat gain and losses between the two groups. Methods: The effect of coat colour on rectal and surface temperatures in Boer goats, classified according to their head pigmentation pattern as dark (DB, N = 11) or light brown (LB, N = 11), exposed to sun and shade, was evaluated. The animals' body and head surface temperatures were measured the same day before, during, and after sun exposure by using infrared thermography. Individual thermographic images were analysed by body regions (rump, leg, neck) and head areas (eye, ear, upper and lower part of the head, and the muzzle). Key results: During solar radiation, all measured variables increased. In the shade, the rump, leg, and neck surfaces remained elevated, whereas the head area cooled down faster, with the highest temperature changes measured for the ear of about 10%. Most surface cooling occurred within 30 min after returning to the shade. Coat colour groups differed only in higher overall muzzle temperature of DB than that of LB goats (P = 0.048). Correlations between rectal and surface temperatures were low to medium, ranging from −0.02 (eye) to 0.31 (muzzle). Conclusions: The head area is suggested as the important thermal window for heat dissipation and selective brain cooling. Light brown-headed animals were more efficient in eliminating the heat gained from solar radiation when returned to shade. Implications: The colouration of the animal's head may play an important role for its heat tolerance. As an easy-to-recognise characteristic, coat colour can serve as a selection trait for local goat populations. In view of global warming, selection for lighter coat colour in domestic ruminants may also become important even under temperate climates. Coat colour plays an important role in heat tolerance of livestock, because dark coat colour may increase animal heat stress as a result of higher absorption of solar radiation. We focused on the influence of head pigmentation of Boer goats and found light brown-headed animals to be more efficient in eliminating the solar heat gained during outdoor grazing when returned to the shade. In view of global warming, breeding for light coat colour in domestic ruminants could alleviate heat stress. [ABSTRACT FROM AUTHOR]

In mammals, the central circadian oscillator is located in the suprachiasmatic nucleus (SCN). Hypothalamus–pituitary–thyroid axis components exhibit circadian oscillation, regulated by both central clock innervation and intrinsic circadian clocks in the anterior pituitary and thyroid glands. Thyroid disorders alter the rhythmicity of peripheral clocks in a tissue‐dependent response; however, whether these effects are influenced by alterations in the master clock remains unknown. This study aimed to characterize the effects of hypothyroidism on the rhythmicity of SCN, body temperature (BT) and metabolism, and the possible mechanisms involved in this signalling. C57BL/6J adult male mice were divided into Control and Hypothyroid groups. Profiles of spontaneous locomotor activity (SLA), BT, oxygen consumption (V̇O2${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$) and respiratory quotient (RQ) were determined under free‐running conditions. Clock gene expression, and neuronal activity of the SCN and medial preoptic nucleus (MPOM) area were investigated in light–dark (LD) conditions. Triiodothyronine (T3) transcriptional regulation of Bmal1 promoter activity was evaluated in GH3‐transfected cells. Hypothyroidism delayed the rhythmicity of SLA and BT, and altered the expression of core clock components in the SCN. The activity of SCN neurons and their outputs were also affected, as evidenced by the loss of circadian rhythmicity in V̇O2${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and RQ and alterations in the neuronal activity pattern of MPOM. In GH3 cells, T3 increased Bmal1 promoter activity in a time‐dependent manner. Thyroid hormone may act as a temporal cue for the central circadian clock, and the uncoupling of central and peripheral clocks might contribute to a wide range of metabolic and thermoregulatory impairments observed in hypothyroidism. Key points: Hypothyroidism alters clock gene expression in the suprachiasmatic nucleus (SCN).Thyroid hypofunction alters the phase of spontaneous locomotor activity and body temperature rhythms.Thyroid hormone deficiency alters the daily pattern of SCN and medial preoptic nucleus neuronal activities.Hypothyroidism alterations are extended to daily oscillations of oxygen consumption and metabolism, which might contribute to the development of metabolic syndrome.Triiodothyronine increases Bmal1 promoter activity acting as temporal cue for the central circadian clock. [ABSTRACT FROM AUTHOR]

The spatial configuration of thermal habitats constrains the thermoregulatory performance of ectotherms. Thermal landscapes also vary through time, which is particularly relevant in seasonal environments such as temperate lakes. Indeed, elevated temperatures in the epilimnion of dimictic lakes during summer could substantially reduce the use of this habitat by cold‐stenothermic fish during the stratified period. The main objective of this study was to evaluate whether thermal habitat fragmentation in stratified lakes modulates accessibility to resources that brook charr, Salvelinus fontinalis, which is a mobile consumer, can track across seasons. More specifically, we hypothesize that reduced access to the littoral habitat during summer enhances foraging opportunities in this habitat during winter. We used an automatic acoustic telemetry system offering full coverage of the lake to continuously record brook charr locations across seasons, and we estimated zoobenthos abundances in the littoral habitat using image processing and semi‐automatic classification. While brook charr concentrate in the metalimnion of the pelagic habitat in summer, most individuals in winter shift to a shallow bay that is unexploited in summer due to thermal constraints. In this habitat, zoobenthos abundance is more than twice as high at the end of the summer compared to littoral habitats close to the thermal refuge in the pelagic habitat. Surprisingly, brook charr showed strong within‐lake site fidelity between two consecutive summers, which suggests that spatial memory could be a key driver of seasonal habitat use in this lacustrine population. Overall, our results suggest that thermal barriers create fragmentation between littoral and pelagic habitats that in turn produces resource opportunities that brook charr can track across seasons. [ABSTRACT FROM AUTHOR]

The objective was to assess if post‐exercise ingestion of carbonated water in a hot environment ameliorates hypotension, enhances cerebral blood flow and heat loss responses, and positively modulates perceptions and mood states. Twelve healthy, habitually active young adults (five women) performed 60 min of cycling at 45% peak oxygen uptake in a hot climate (35°C). Subsequently, participants consumed 4°C carbonated or non‐carbonated (control) water (150 and 100 mL for males and females regardless of drink type) at 20 and 40 min into post‐exercise periods. Mean arterial pressure decreased post‐exercise at 20 min only (P = 0.032) compared to the pre‐exercise baseline. Both beverages transiently (∼1 min) increased mean arterial pressure and middle cerebral artery mean blood velocity (cerebral blood flow index) regardless of post‐exercise periods (all P ≤ 0.015). Notably, carbonated water ingestion led to greater increases in mean arterial pressure (2.3 ± 2.8 mmHg vs. 6.6 ± 4.4 mmHg, P < 0.001) and middle cerebral artery mean blood velocity (1.6 ± 2.5 cm/s vs. 3.8 ± 4.1 cm/s, P = 0.046) at 20 min post‐exercise period compared to non‐carbonated water ingestion. Both beverages increased mouth exhilaration and reduced sleepiness regardless of post‐exercise periods, but these responses were more pronounced with carbonated water ingestion at 40 min post‐exercise (mouth exhilaration: 3.1 ± 1.4 vs. 4.7 ± 1.7, P = 0.001; sleepiness: −0.7 ± 0.91 vs. −1.9 ± 1.6, P = 0.014). Heat loss responses and other perceptions were similar between the two conditions throughout (all P ≥ 0.054). We show that carbonated water ingestion temporarily ameliorates hypotension and increases the cerebral blood flow index during the early post‐exercise phase in a hot environment, whereas it enhances mouth exhilaration and reduces sleepiness during the late post‐exercise phase. What is the central question of this study?Post‐exercise hypotension can cause syncope, and an established practical countermeasure to mitigate this response is currently lacking: does ingestion of carbonated water restore post‐exercise hypotension and positively modulate mood states?What is the main finding and its importance?Carbonated water ingestion transiently increased blood pressure and cerebral blood flow index post‐exercise in the heat. Additionally, carbonated water ingestion increased exhilaration for the mouth and decreased sleepiness post‐exercise. Thus, carbonated water ingestion may mitigate post‐exercise hypotension, increase cerebral perfusion and improve mood states. [ABSTRACT FROM AUTHOR]

Lors de l'activité physique, les sportifs atteints d'une lésion de la moelle épinière doivent faire face à des problèmes de thermorégulation. En fonction des conditions climatiques et du niveau de la lésion médullaire, les répercussions sur la température corporelle sont différentes. Cette étude a pour objectif d'obtenir une vue d'ensemble sur les techniques de refroidissement et de réchauffement mise en place par les paraplégiques et les tétraplégiques lors de la pratique d'une activité physique. Utilisation de la méthode PICO (participants, intervention/exposition, comparaison, outcomes) afin de mettre en évidence les termes à utiliser pour la recherche des articles scientifiques. Lors d'une activité physique en ambiance chaude, différentes techniques de refroidissement ont été mises en évidence : vestes de refroidissement, pulvérisation d'eau sur le corps, ingestion de substances froides, refroidissement des mains et des pieds ou combinaison de plusieurs de ces techniques. Toutes ces techniques permettent de freiner l'augmentation de la température centrale comparée à un groupe contrôle. En ambiance froide, les sportifs tentent de se réchauffer à l'aide de vêtements chauds ou par la mise en place de stratégies efficaces pour maintenir leur température centrale entre la période de l'échauffement et la compétition. En ce qui concerne le sport en ambiance chaude, il existe différentes stratégies de refroidissement qui sont utilisées. Cependant, il y a un manque de preuves quant à la plus efficace. Pour le sport en ambiance froide, il n'y a que très peu d'études qui traitent de ce sujet. Des recherches doivent encore être réalisées afin de pouvoir objectiver quelles sont les meilleures techniques pour se réchauffer. During physical activity, athletes with a spinal cord injury have to face thermoregulation problems due to an alteration of their nervous system. The repercussion of the core body temperature depends on the climate. The aim of this revue was to obtain an overview of the cooling and warming techniques used by paraplegics and tetraplegics when practicing a physical activity. We used the PICO (participants, intervention/exposition, comparison, outcomes) method to highlight the terms we need for the search of scientific articles. During a physical activity in a hot environment, different cooling techniques have been demonstrated: cooling jackets, spraying water on the body, ingestion of cold substances, cooling of hands and feet or a combination of several of these techniques. All of these techniques have been shown to slow down the increase in core temperature compared to a control group. In a cold environment, athletes try to warm-up with warm clothes or by implementing effective strategies to maintain their core temperature between the warm-up period and the competition. Regarding sports in hot environments, there are different cooling strategies that are used. However, there is a lack of evidence as to which is most effective. For sport in a cold environment, there are very few studies that deal with this subject. Research is still needed to establish which techniques are the best to warm-up. [ABSTRACT FROM AUTHOR]

Exercise mechanical efficiency typically falls within the range of approximately 20 to 25%. This means that a great part of the metabolic energy converted to generate movement is released as heat. Therefore, the rise in core temperature during endurance exercise in humans is proportional to generated work. Cutaneous vasodilation occurs when the core temperature threshold is reached. The rise in heart rate in response to thermal stress is a cardiovascular response that increases cardiac output and skin blood flow. The cardiovascular response during endurance exercise is a complex phenomenon potentially influenced by the involvement of nitric oxide in active thermoregulatory vasodilation. Excessive exercise can create high oxidative stress by disrupting the balance between free radicals' production and scavenging, resulting in impaired cardiovascular function. The above considerations are related to the severity and duration of endurance exercise. The first focus of this narrative review is to provide an updated understanding of cardiovascular function during endurance exercise. We aim to explore the potential role of oxidative stress in causing cardiovascular dysfunction during endurance exercise from a fresh perspective. Additionally, we aim to identify the primary factors contributing to cardiovascular risk during strenuous prolonged exercise by highlighting recent progress in this area, which may shed light on previously unexplained physiological responses. To ascertain the effect of endurance exercise on cardiovascular function and dysfunction, a narrative review of the literature was undertaken using PubMed, ScienceDirect, Medline, Google Scholar, and Scopus. The review highlighted that high oxidative stress (due to high levels of catecholamines, shear stress, immune system activation, and renal dysfunction) leads to a rise in platelet aggregation during endurance exercise. Importantly, we clearly revealed for the first time that endothelial damage, vasoconstriction, and blood coagulation (inducing thrombosis) are potentially the primary factors of cardiovascular dysfunction and myocardial infarction during and/or following endurance exercise. [ABSTRACT FROM AUTHOR]

This article describes the development and validation of accurate whole body sweat rate prediction equations for individuals performing indoor cycle ergometer and treadmill exercise, where power output can be measured or derived from simple inputs. For cycle ergometry, 112 trials (67 participants) were used for model development and another 56 trials (42 participants) for model validation. For treadmill exercise, 171 trials (67 participants) were used for model development and another 95 trials (63 participants) for model validation. Trials were conducted over a range of dry-bulb temperature (20°C to 40°C), relative humidity (14% to 60%), and exercise intensity (∼40% to 85% of peak aerobic power) conditions, which were matched between model development and model validation. Whole body sweat rates were measured, and proprietary prediction models were developed (accounting for all relevant biophysical factors) and then validated. For model validation, mean absolute error for predicted sweating rate was 0.01 and 0.02 L·h−1 for cycle and treadmill trials, respectively. The 95% confidence intervals were modest for cycle ergometer (+0.25 and −0.22 L·h−1) and treadmill exercise (+0.33 and −0.29 L·h−1). The accounted for variance between predicted and measured values was 92% and 78% for cycle and treadmill exercise, respectively. Bland–Altman analysis indicated that zero and one predicted value exceeded the a priori acceptable level of agreement (equivalent to ±2% of total body mass in 3 h) for cycle and treadmill exercise, respectively. There were fewer trials with female subjects, but their values did not differ from those expected for males. This is the foremost study to develop and validate whole body sweat rate prediction equations for indoor treadmill and cycle ergometer exercise of moderate to high intensity. These prediction equations are publicly available for use (https://sweatratecalculator.com). NEW & NOTEWORTHY: This study presents the development of new proprietary whole body sweat rate prediction models for people exercising indoors on a cycle ergometer or treadmill using simple input parameters and delivered through a publicly available online calculator: https://sweatratecalculator.com. In an independent validation group, the predictive models for both indoor cycling and treadmill exercise were accurate across moderate to high exercise intensities in temperate to hot conditions. These equations will enable individualized hydration management during physical training and exercise physiology experiments. [ABSTRACT FROM AUTHOR]

Thermo-regulating textiles incorporating Phase-Change Materials (PCMs) have emerged as innovative substances that automatically adapt to changes in environmental and body temperature. This paper presents an approach to develop a PCM-loaded composite yarn for potential use in medical textiles. Paraffin wax-based PCM nanocapsules were synthesized and integrated into cotton fibers during the ring spinning process. Subsequently, a composite core–shell-structured yarn was fabricated using electrospinning, comprising a cotton/PCM core and a poly (l-lactic acid) (PLLA)/PCM nanofibrous shell. Morphological analysis confirmed the successful formation of the core–shell structure and the uniform distribution of PCM nanocapsules within the fibers. The composite yarns exhibited reduced diameters with increasing PCM nanocapsule content. Thermal analysis revealed that the incorporation of PCMs resulted in decreased glass transition and cold crystallization temperatures of the PLLA nanofibers. Additionally, the presence of PCMs increased the crystallinity of PLLA fibers. According to the thermoregulation test results, the presence of PCM in its structure affected the heating and cooling behavior of the yarns. The composite yarns were further functionalized by incorporating Vancomycin as an antibiotic agent for medical dressing applications. This progress signifies an improved thermoregulation, offering potential applications in wound care and other medical settings. [ABSTRACT FROM AUTHOR]

Hypothermia during obstetric spinal anaesthesia is a common and important problem, yet temperature monitoring is often not performed due to the lack of a suitable, cost-effective monitor. This study aimed to compare a noninvasive core temperature monitor with two readily available peripheral temperature monitors during obstetric spinal anaesthesia. We undertook a prospective observational study including elective and emergency caesarean deliveries, to determine the agreement between affordable reusable surface temperature monitors (Welch Allyn SureTemp® Plus oral thermometer and the Braun 3-in-1 No Touch infrared thermometer) and the Dräger T-core© (using dual-sensor heat flux technology), in detecting thermoregulatory changes during obstetric spinal anaesthesia. Predetermined clinically relevant limits of agreement (LOA) were set at ± 0.5 °C. We included 166 patients in our analysis. Hypothermia (heat flux temperature < 36 °C) occurred in 67% (95% CI 49 to 78%). There was poor agreement between devices. In the Bland-Altman analysis, LOA for the heat flux monitor vs. oral thermometer were 1.8 °C (CI 1.7 to 2.0 °C; bias 0.5 °C), for heat flux monitor vs. infrared thermometer LOA were 2.3 °C (CI 2.1 to 2.4 °C; bias 0.4 °C) and for infrared vs. oral thermometer, LOA were 2.0 °C (CI 1.9 to 2.2 °C; bias 0.1 °C). Error grid analysis highlighted a large amount of clinical disagreement between methods. While monitoring of core temperature during obstetric spinal anaesthesia is clinically important, agreement between monitors was below clinically acceptable limits. Future research with gold-standard temperature monitors and exploration of causes of sensor divergence is needed. [ABSTRACT FROM AUTHOR]

Animal coloration serves a variety of visually related functions in nature (e.g. mate choice, aposematism and camouflage) but the pigments in integumentary tissues such as skin, scales and feathers may also serve functions unrelated to the visual environment (e.g. temperature regulation, detoxification and pollutant protection). Our understanding of the significance of the non‐visual functions of animal integumentary pigments, as well as how they interact with the visually related functions to shape animal visual systems, remains limited. Furthermore, due to their important roles in shaping species interactions and mediating interactions in the environment, animal colour traits are likely to be impacted by global change (e.g. increased temperatures, altered habitat quality and quantity, increased environmental stochasticity, pollutants and novel species assemblages). Considering the effects of global change on both visual and non‐visual functions is important for understanding whether the selection is acting directly on the pigment or on coloration. Since changing the trait distributions can then lead to changes in visual systems, we advocate for studies to consider all potential functions of integumentary pigments, both visual and non‐visual functions and their interaction. Towards this goal, we first highlight common functions of pigments with a focus on non‐visual functions across animal systems. Then we synthesize our current understanding of how global change can impact pigmentation and discuss factors that can modify the interactions between climate change and pigment function. Lastly, we discuss how changes in colour traits can impact visual systems and provide an example using amphibians and their responses to climate change as a model. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Thermoregulation is impaired in individuals with a spinal cord lesion (SCI), affecting sweat capacity, heat loss, and core temperature. This can be particularly problematic for athletes with SCI who exercise in hot and humid conditions, like those during the Tokyo 2020 Paralympic Games. Heat acclimation can support optimal preparation for exercise in such challenging environments, but evidence is limited in endurance athletes with SCI. We evaluated whether seven consecutive days of exercise in the heat would result in heat acclimation. Five elite para-cycling athletes with SCI participated (two females, three males, median (Q1-Q3) 35 (31–51) years, four with paraplegia and one with tetraplegia). All tests and training sessions were performed in a heat chamber (30°C and 75% relative humidity). A time-to-exhaustion test was performed on day 1 (pretest) and day 7 (posttest). On days 2–6, athletes trained daily for one hour at 50–60% of individual peak power (PPeak). Comparing pretest and posttest, all athletes increased their body mass loss (p=0.04), sweat rate (p=0.04), and time to exhaustion (p=0.04). Effects varied between athletes for core temperature and heart rate. All athletes appeared to benefit from our heat acclimation protocol, helping to optimize their preparation for the Tokyo 2020 Paralympic Games. [ABSTRACT FROM AUTHOR]

Summary: Current estimates of temperature effects on plants mostly rely on air temperature, although it can significantly deviate from leaf temperature (Tleaf). To address this, some studies have used canopy temperature (Tcan). However, Tcan fails to capture the fine‐scale variation in Tleaf among leaves and species in diverse canopies.We used infrared radiometers to study Tleaf and Tcan and how they deviate from air temperature (ΔTleaf and ΔTcan) in multispecies tropical tree plantations at three sites along an elevation and temperature gradient in Rwanda.Our results showed high Tleaf (up to c. 50°C) and ΔTleaf (on average 8–10°C and up to c. 20°C) of sun‐exposed leaves during 10:00 h–15:00 h, being close to or exceeding photosynthetic heat tolerance thresholds. These values greatly exceeded simultaneously measured values of Tcan and ΔTcan, respectively, leading to strongly overestimated leaf thermal safety margins if basing those on Tcan data. Stomatal conductance and leaf size affected Tleaf and Tcan in line with their expected influences on leaf energy balance.Our findings highlight the importance of leaf traits for leaf thermoregulation and show that monitoring Tcan is not enough to capture the peak temperatures and heat stress experienced by individual leaves of different species in tropical forest canopies. [ABSTRACT FROM AUTHOR]

Background and Purpose: We extend the characterization of the TRPM8 antagonist VBJ103 with tests of selectivity, specificity and distribution, therapeutic efficacy of systemic administration against oxaliplatin‐induced cold hyperalgesia and the impact of systemic administration on core body temperature (CBT). Experimental Approach: Selectivity at human TRPA1 and TRPV1 as well as in vitro safety profiling was determined. Effects of systemic administration of VBJ103 were evaluated in a model of oxaliplatin‐induced cold hyperalgesia. Both peripheral and centrally mediated effects of VBJ103 on CBT were assessed with radiotelemetry. Key Results: VBJ103 had no antagonist activity at TRPV1 and TRPA1, but low potency TRPA1 activation. The only safety liability detected was partial inhibition of the dopamine transporter (DAT). VBJ103 delivered subcutaneously dose‐dependently attenuated cold hypersensitivity in oxaliplatin‐treated mice at 3, 10 and 30 mg·kg−1 (n = 7, P < 0.05). VBJ103 (30 mg·kg−1) antinociception was influenced by neither the TRPA1 antagonist HC‐030031 nor the DAT antagonist GBR12909. Subcutaneous administration of VBJ103 (3, 10 and 30 mg·kg−1, but not 100 or 300 mg·kg−1, n = 7) decreased CBT (2°C). Intraperitoneal (i.p.) administration of VBJ103 (3, 10 and 30 mg·kg−1) dose‐dependently decreased CBT to an extent larger than that detected with subcutaneous administration. Intracerebroventricular (i.c.v.) administration (306 nmol/1 μL; n = 5) did not alter CBT. Conclusions and Implications: We achieve therapeutic efficacy with subcutaneous administration of a novel TRPM8 antagonist that attenuates deleterious influences on CBT, a side effect that has largely prevented the translation of TRPM8 as a target. [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]

Sunscreens may affect thermoregulation and sweating during exercise in warm climates. In this study, we compared the effects of three sunscreens on local sweating rate (LSR) during exercise under controlled conditions (32°C, relative humidity 55%). Fifteen subjects (8 men, 7 women) underwent 20-min cycles in four randomized conditions: control (CON), sunscreen A (SSA), sunscreen B (SSB) and sunscreen C (SSC). LSR was measured by a patch on the scapular region (p < .001). CON showed higher LSR (182.21 μL/min·dm2, CI95% 168 to 195 μL/min·dm2) compared to SSA (142.10 μL/min·dm2, CI95% 128 to 155 μL/min·dm2), SSB (158.06 μL/min·dm2, CI95% 144 to 171 μL/min·dm2), and SSC (159.00 μL/min·dm2, CI95% 145 to 172 μL/min·dm2). In men, SSA showed lower LSR compared to CON, SSB, and SSC (p < .05). On the other hand, no statistically significant differences were found in LSR between SSB, SSC, and CON conditions. In women, CON was superior to all sunscreens in LSR (p < .001), and there was no difference between them (SSA, SSB, SSC, p > .05). Sunscreen reduced LSR during moderate exercise in a hot and moderate humidity environment compared to CON, especially SSA in men and all sunscreens in women. [ABSTRACT FROM AUTHOR]

We assessed newborn lambs from two hair-coat sheep breeds, the black Santa Ines (n = 29) and white Dorper (n = 26), to determine how they behaviourally and physiologically respond to the prevailing thermal conditions in an equatorial semi-arid environment. Measurements of hair-coat surface temperature, rectal temperature and the lambs' exposure to sun were recorded across the first 24 h of life every hour, after the lambs had received colostrum. Lambs and ewes were kept in a lambing pen and could freely move between a shaded area or be exposed to sun. During the study period, the air temperature ranged between 20 ºC and 34 ºC. When exposed to sun, lambs and ewes could experience as much as 1200 W m-2 of solar irradiance. Santa Ines lambs exhibited higher (highest density interval at 95%, HDI) hair-coat surface temperatures than did Dorper lambs. Overall, both Santa Ines and Dorper lambs sustained homeothermy, with a mean rectal temperature ranging from 38.7 ºC to 39.1 ºC between night and daytime phase, and a mean amplitude of ~ 0.8 ºC. Nevertheless, from 10:00 to 15:00, some lambs were found to be moderately hyperthermic. Five Santa Ines and three Dorper lambs had rectal temperatures above 40 ºC, and one Santa Ines lamb, while exposed to sun, had a rectal temperature of 41.3 ºC. Over this time period, lambs were more likely to move to shade (HDI at 95%). From 00:00 to 06:00, despite the air temperature being lower than the hair-coat surface, favouring high rates of sensible heat loss to the environment, no lamb exhibited signs of hypothermia (rectal temperature < 37.5 ºC). In conclusion, haired newborn lambs coped well with high levels of radiant heat during the daytime and lower temperatures at night. However, providing access to shade during the daytime is important to improve the welfare of newborn lambs delivered in equatorial semi-arid regions. [ABSTRACT FROM AUTHOR]

Simple Summary: Warm-blooded animals (like mammals and birds) living in colder climates (higher latitudes or elevations) tend to have larger bodies compared to their relatives in warmer areas. This pattern has been interpreted in terms of heat budget: since the surface area-to-volume ratio decreases with increasing size, larger animals need to produce relatively less heat to maintain stable body temperatures (Bergmann's rule). This mechanism cannot operate in cold-blooded animals, like most insects, as they do not produce heat. In these animals, a reverse pattern is frequently observed, as an increased surface area-to-volume ratio may allow for more rapid heating and cooling. However, selection for more stable internal temperatures might lead to smaller surface area-to-volume ratios also in cold-blooded animals, leading to a negative correlation between body size and temperature. An analysis conducted on tenebrionids along an elevational gradient in Central Italy revealed that, on average, their surface area-to-volume ratios decline with increasing elevation, thus indicating the importance of heat conservation. However, while in species living under bark or in rotten wood, body size (mass and volume) tends to increase with elevation, in ground-dwelling species, it declines up to about 1000 m and then increases. This suggests that a reduction in resource availability with increasing elevation limits body size in ground-dwelling species up to a certain elevation but not in those living under bark, which benefit from more microclimatically stable conditions and constant resources and need energy for overwintering. In endotherms, body size tends to increase with elevation and latitude (i.e., with decreasing temperatures) (Bergmann's rule). These patterns are explained in terms of heat balance since larger animals need to produce less heat relative to their size to maintain stable body temperatures. In ectotherms like most insects, where this mechanism cannot operate, a reverse pattern is frequently observed, as a higher surface area-to-volume ratio in colder climates may allow for more rapid heating and cooling. However, patterns of increasing body size with decreasing temperatures can also be observed in ectotherms if selection for more stable internal temperatures leads to smaller surface area-to-volume ratios. Data on tenebrionids from Latium (Central Italy) were used to model elevational variations in average values of body size (total length, mass and volume) and surface area-to-volume ratio. Analyses were performed by considering the whole fauna and two ecological groups separately: ground-dwelling species (geophilous) and arboreal (xylophilous) species. The surface area-to-volume ratios declined with increasing elevation in all cases, indicating that the need for heat conservation is more important than rapid heating and cooling. However, in xylophilous species (which typically live under bark), body size increased with increasing elevation, and in geophilous species, an opposite pattern was observed up to about 1000 m, followed by an increasing pattern. This suggests that a reduction in resource availability with elevation limits body size in geophilous species up to a certain elevation but not in xylophilopus species, which benefit from more climatically stable conditions and constant resources and need energy for overwintering. [ABSTRACT FROM AUTHOR]

Body temperature is primarily regulated by the hypothalamus, ensuring proper metabolic function. Envenomation by Phoneutria nigriventer can cause symptoms such as hypothermia, hyperthermia, sweating, and shivering, all related to thermoregulation. This study aims to analyze and identify components of the venom that affect thermoregulation and to evaluate possible mechanisms. Rats were used for thermoregulation analysis, venom fractionation by gel filtration and reverse-phase chromatography (C18), and sequencing by Edman degradation. The venom exhibited hypothermic effects in rats, while its fractions demonstrated both hypothermic (pool II) and hyperthermic (pool III) effects. Further separations of the pools with C18 identified specific peaks responsible for these effects. However, as the peaks were further purified, their effects became less significant. Tests on U87 human glioblastoma cells showed no toxicity. Sequencing of the most active peaks revealed masses similar to those of the Tachykinin and Ctenotoxin families, both known to act on the nervous system. The study concludes that molecules derived from venom can act synergistically or antagonistically. Additionally, toxins that affect thermoregulation are poorly studied and require further characterization. These toxins could potentially serve as sources for the development of new thermoregulatory drugs. [ABSTRACT FROM AUTHOR]

Elite football requires comprehensive monitoring to optimize player performance and minimize injury risk. In this sense, thermography is a validated way to monitor football players' load, when using this technology is essential to realize an acclimatization for assessing thermal asymmetry, a crucial variable for injuries. This study aimed to investigate the impact of acclimatization on thermal patterns in elite junior football players. For this purpose, a four-week study was conducted with an elite youth team, involving thermography sessions at three distinct stages: immediately upon arrival, after 5 min, and after 10 min in a room with temperature and humidity set at the same values (20°C and 50%). Results indicated that while temperature decreased over time, significant differences in thermal asymmetry were observed only in some muscles; the most significant ones were in the hamstrings. This discrepancy in hamstring asymmetry may be attributed to uneven sedentary postures preceding the first thermographic photograph and players arriving either by running or by walking briskly to the test. In conclusion, while acclimatization may be crucial for hamstrings evaluation, it might not be as significant for other muscle groups or joints. The potential acclimatization difference for each muscle underscores the need for future investigations. [ABSTRACT FROM AUTHOR]

Simple Summary: Perinatal twin lamb mortality reduces productivity and reproductive efficiency in Australian sheep meat and wool enterprises. This study investigated whether supplementing 4 g of betaine into the diets of twin-bearing Merino ewes during late pregnancy would improve lamb viability measures and survival to weaning under field conditions. The results indicated that dietary supplementation with betaine increased plasma creatine concentrations in ewes at day 130 of gestation and lamb rectal temperature within 4–24 h following birth. While the findings of this study provide some new, promising results, more research in the field is required before supplementation with betaine during late gestation can be used as an on-farm strategy to improve lamb viability and survival. Twin lamb mortality is a significant economic problem impacting the Australian sheep industry. Maternal betaine supplementation improved lamb vigour and early post-natal survival when ewes and lambs were housed indoors, suggesting that betaine may be beneficial to feed under extensive pasture systems. This study investigated whether maternal betaine supplementation during late gestation would improve Merino twin lamb live weight, thermoregulation, vigour and survival to weaning under field conditions. Ewes received dietary betaine at either 0 g/day (CTL; n = 115) or 4 g/day from day 110 of gestation (dG 110) until ~49 days post-partum (pp) (BET; n = 115). Measures indicative of lamb viability and survival were collected within 4–24 h of birth and at ~49 days pp and ~93 days pp. BET ewes had higher creatine and creatinine concentrations at dG 130 than CTL ewes (p < 0.05). BET lambs had a higher rectal temperature within 4–24 h following birth than CTL lambs (p < 0.05). CTL lambs were heavier at ~49 days pp and grew faster from birth to ~49 days pp than BET lambs (both p < 0.05). The time taken after release from the researcher to first suckling was quicker in the CTL lambs than BET lambs (p < 0.05). This study demonstrated that supplementing betaine increased creatine concentration in twin-bearing ewes and thermoregulatory capacity in neonatal lambs under extensive grazing systems. [ABSTRACT FROM AUTHOR]

It is commonly thought that steady-state thermoregulatory responses are achieved within 30–90 min of compensable heat stress. However, this assumption is based on measurements of whole body heat exchange during exercise, which stabilize (equilibrate) more rapidly than deep body temperatures, especially under resting conditions. To support the design of ecologically relevant heat exposure studies, we quantified equilibrium times for deep body temperature, as indexed by rectal temperature, in young and older adults resting in the heat. We also evaluated the lag in rectal temperature equilibrium relative to whole body heat storage (direct calorimetry). Equilibrium times were estimated with data from two laboratory-based trials (NCT04353076 and NCT04348630) in which 83 adults aged 19–80 yr (34 female) were exposed to simulated heat-wave conditions for 8–9 h. When assessed at the group level, it took rectal temperature 3.3 [bootstrap 95% confidence interval: 2.9–3.9] h to reach thermal equilibrium (<0.05°C/h rate of change) in young adults exposed to 40°C, 9% relative humidity (RH). In older adults, who were exposed to a greater range of conditions (31°C–40°C, 9–45% RH), equilibrium times were longer, ranging from 4.4 [3.8–5.3] to 5.2 [4.9–5.4] h. Furthermore, rectal temperature equilibrium was delayed 0.9 [0.5–1.4] and 1.8 [0.9–2.7] h compared with whole body heat storage in young and older adults, respectively (only assessed in 40°C, 9% RH). Individual-level equilibrium times ranged from 1 to 8 h. These findings highlight the importance of ecologically relevant exposure durations in translational research assessing the physiological impacts of hot weather. NEW & NOTEWORTHY: Deep body (rectal) temperature took 3–5 h on average and up to 6–8 h at the individual level to reach thermal equilibrium in young and older adults resting in the heat. Furthermore, stable rectal temperatures were delayed by up to 2 h relative to the achievement of heat balance (0 kJ/min rate of heat storage). We provide the first quantification of the temporal profiles of thermal strain during extended rest in conditions simulating hot weather. [ABSTRACT FROM AUTHOR]

Individuals over the age of 65 yr are the most vulnerable population during severe environmental heat events, experiencing worse health outcomes than any other age cohort. The risk is greater in older women than in age-matched men; however, whether that reflects a greater susceptibility to heat in women, or simply population sex proportionality, is unclear. Seventy-two participants (29 M/43 F) aged 40–92 yr were exposed to progressive heat stress at a metabolic rate designed to reflect activities of daily living. Experiments were conducted in both hot-dry (HD; up to 53°C; ≤25% rh) and warm-humid (WH; ∼35°C; ≥50% rh) environments. After critical limits were determined for each condition, forward stepwise multiple linear regression analyses were conducted with net metabolic rate (Mnet) and age entered into the model first, followed by sex, body mass (mb), maximal oxygen consumption (V̇ o 2max), body surface area, and LDL cholesterol. After accounting for Mnet and age, sex further improved the regression model in the HD environment ( R adj 2 = 0.34, P < 0.001) and the WH environment ( R adj 2 = 0.36, P < 0.005). Sex explained ∼15% of the variance in critical environmental limits in HD conditions and 12% in WH conditions. Heat compensability curves were shifted leftward for older women, indicating age- and sex-dependent heat vulnerability compared with middle-aged women and older men in WH (P = 0.007, P = 0.03) and HD (P = 0.001, P = 0.01) environments. This reflects the heterogeneity of thermal-balance thresholds associated with aging relative to those seen in young adults and suggests that older females are more vulnerable than their age-matched male counterparts. NEW & NOTEWORTHY: In contrast to young adults, there are sex differences in critical environmental limits in middle-aged and older adults. Older women exhibit lower critical environmental limits in both humid and dry extreme environments demonstrated by a leftward shift in heat compensability curves. These data confirm a true sex difference in heat vulnerability of older adults and support the epidemiological mortality data from environmental heat waves. [ABSTRACT FROM AUTHOR]

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. In countries with pasture-based dairy systems and relatively cold winters, such as New Zealand, it is common to manage pregnant, nonlactating cows on forage crop paddocks rather than pasture, due to slow pasture growth rates. Wintering dairy cattle on grazed crops can compromise welfare if wet and muddy underfoot conditions occur, which can reduce lying. This study investigated behavioral and physiological indicators of welfare of cows under 2 wintering practices: cows managed on and grazed kale crop (Brassica oleracea), and cows managed on pasture with baled hay. Following dry-off (d 0), 80 cows were randomly assigned to 1 of the 2 wintering practices (40 cows/practice) and monitored between d 4 and 32 (phase 1). During this period, lying and stepping behavior was continuously recorded using leg-based accelerometers. Blood samples were obtained at d 0 and 32 for measurements of thyroxine (T4), nonesterified fatty acids (NEFA), white blood cells (WBC), and red blood cells. All data for phase 1 were presented descriptively due to the lack of treatment replication. Daily mean air temperature during this period was 5.2°C (range: 0.0–10.7°C), and rainfall was 1.1 mm/d (range: 0–5.6mm/d). Between d 4 and 32, cows in both groups spent similar amounts of time lying (pasture with hay cows: 8.9 h/24 h ± 2.57, kale crop cows: 8.7 h/24 h ± 3.06, mean ± SEM). Both groups reduced their lying on wet and cold days, and there was evidence of rebound lying once unfavorable weather conditions stopped. Cows on kale crop had numerically higher NEFA and lower WBC compared with cows managed on pasture, although most physiological values were within normal ranges. In a second phase of the study (d 34 and 35), cows were managed under controlled, replicated conditions in the 2 wintering practices using typical on-farm stocking rates (2 or 4 cows per group in the pasture with hay and kale crop treatments, respectively; n = 10 groups/treatment). During this period, cow behavior, skin and surface temperatures, hygiene scores, feed intakes, and ground conditions were measured. Weather conditions during the 48-h exposure were mostly cold and dry (mean air temperature: 7.8°C, range: −2.2 to 20.5°C). Cows managed on pasture with hay spent more time lying down on the first day of exposure; however, this was likely due to less space being available to kale cows on this day. Cows managed on pasture with hay ruminated more than cows on kale crop on both days of observations (d 1: 37.9% vs. 30.9% of observations, d 2: 36.8% vs. 28.7% of observations for pasture with hay and kale crop groups, respectively) and were lying more often in postures indicative of greater thermal comfort. Cows managed on pasture with hay had higher skin and surface temperatures compared with cows on kale crop, whereas cows on kale crop had dirtier coats. Results suggest that opportunities for thermal comfort were greater for cows managed on pasture with hay bales, which may be due to increased rumination activities and more insulated lying areas. [ABSTRACT FROM AUTHOR]

Purpose: To determine the effect of taurine supplementation on sweating and core temperature responses, including the transition from compensable to uncompensable heat stress, during prolonged low-intensity exercise of a fixed-heat production (~ 200W/m2) in hot conditions (37.5 °C), at both fixed and incremental vapour-pressure. Methods: Fifteen females (n = 3) and males (n = 12; 27 ± 5 years, 78 ± 9 kg, V ˙ O2max 50.3 ± 7.8 mL/kg/min), completed a treadmill walking protocol (~ 200W/m2 heat production [Ḣprod]) in the heat (37.5 ± 0.1 °C) at fixed-(16-mmHg) and ramped-humidity (∆1.5-mmHg/5-min) following 1 week of oral taurine supplementation (50 mg/kg/bm) or placebo, in a double-blind, randomised, cross-over design. Participants were assessed for whole-body sweat loss (WBSL), local sweat rate (LSR), sweat gland activation (SGA), core temperature (Tcore), breakpoint of compensability (Pcrit) and calorimetric heat transfer components. Plasma volume and plasma taurine concentrations were established through pre- and post-trial blood samples. Results: Taurine supplementation increased WBSL by 26.6% and 5.1% (p = 0.035), LSR by 15.5% and 7.8% (p = 0.013), SGA (1 × 1 cm) by 32.2% and 29.9% (p < 0.001) and SGA (3 × 3 cm) by 22.1% and 17.1% (p = 0.015) during the fixed- and ramped-humidity exercise periods, respectively. Evaporative heat loss was enhanced by 27% (p = 0.010), heat-storage reduced by 72% (p = 0.024) and Pcrit was greater in taurine vs placebo (25.0-mmHg vs 21.7-mmHg; p = 0.002). Conclusion: Taurine supplementation increased sweating responses during fixed Ḣprod in hot conditions, prior to substantial heat strain and before the breakpoint of compensability, demonstrating improved thermoregulatory capacity. The enhanced evaporative cooling and reduced heat-storage delayed the subsequent upward inflection in Tcore—represented by a greater Pcrit—and offers a potential dietary supplementation strategy to support thermoregulation. [ABSTRACT FROM AUTHOR]

Blood lactate concentration during exercise is a reliable indicator of energy metabolism and endurance performance. Lactate is also present in sweat, and sweating plays an important role in thermoregulation, especially in hot conditions. Recently, wearable sensors have enabled the real-time and noninvasive measurement of sweat lactate concentration, potentially serving as an alternative indicator of blood lactate response. However, the evidence regarding the relationship between sweat and blood lactate responses during incremental exercise in hot conditions is lacking. In a randomized cross-over design, six highly trained male runners completed two incremental treadmill tests under normal (20°C/50%RH) or hot (30°C/50%RH) conditions. The tests include 3-min running stages and 1-min recovery, starting at 12 km/h and increasing by 1 km/h at each stage. Blood and sweat lactate concentrations were measured at each stage to determine blood and sweat lactate thresholds (LT). Blood lactate concentrations were higher under hot conditions (p < 0.01), but there was no difference in the response pattern or velocity at blood LT between conditions. Significant early increase (p < 0.01) in sweat lactate and low velocity at sweat LT (p < 0.05) were observed under hot conditions. A significant correlation between blood and sweat lactate concentrations was found under normal conditions (p < 0.001) but not under hot conditions, and no significant correlations were observed between the velocity at blood and sweat LT. In conclusion, sweat lactate concentration does not consistently reflect blood lactate concentration during incremental exercise. [ABSTRACT FROM AUTHOR]

The likelihood of exposure to overheated indoor environments is increasing as climate change is exacerbating the frequency and severity of hot weather and extreme heat events (EHE). Consequently, vulnerable populations will face serious health risks from indoor overheating. While the relationship between EHE and human health has been assessed in relation to outdoor temperature, indoor temperature patterns can vary markedly from those measured outside. This is because the built environment and building characteristics can act as an important modifier of indoor temperatures. In this narrative review, we examine the physiological and behavioral determinants that influence a person's susceptibility to indoor overheating. Further, we explore how the built environment, neighborhood-level factors, and building characteristics can impact exposure to excess heat and we overview how strategies to mitigate building overheating can help reduce heat-related mortality in heat-vulnerable occupants. Finally, we discuss the effectiveness of commonly recommended personal cooling strategies that aim to mitigate dangerous increases in physiological strain during exposure to high indoor temperatures during hot weather or an EHE. As global temperatures continue to rise, the need for a research agenda specifically directed at reducing the likelihood and impact of indoor overheating on human health is paramount. This includes conducting EHE simulation studies to support the development of consensus-based heat mitigation solutions and public health messaging that provides equitable protection to heat-vulnerable people exposed to high indoor temperatures. [ABSTRACT FROM AUTHOR]

The thermosensory system is relevant to both the conceptualization and treatment of depression. There is evidence that depression is associated with changes in thermoregulatory functioning, and that thermosensory pathways can be recruited to influence affect and reduce depressive symptoms. In this study, we investigated the relationship between severity of depressive symptoms and changes to measures of subjective experiences associated with thermoregulatory processes as well as the relationship between severity of depressive symptoms and affective responses to warm stimuli, specifically frequency of warmth-seeking behavior. Participants (N = 529) completed measures of depressive symptoms, subjective experiences associated with thermoregulatory processes (i.e., perceived sweating and preferred ambient temperature) and frequency of warmth-seeking behavior (e.g., long hot baths, saunas, etc.). We demonstrate that, controlling for age and gender, greater severity of depressive symptoms is associated with greater perceived sweating and lower preferred ambient temperature. Furthermore, we demonstrate that greater severity of depressive symptoms is associated with more frequent warmth-seeking behavior, and that something other than thermal preference (i.e., stated preference for warmer temperature) is driving this behavior. These data highlight the importance of incorporating the thermoregulatory system in our conceptualization of the pathophysiology of depression and support the potential to recruit thermosensory pathways to target depressive symptoms. [ABSTRACT FROM AUTHOR]

This study aimed to investigate seasonal heat acclimatization in active adolescents following summer. Fifteen (5 females) active adolescents (14.6 ± 1.0 y) completed a 45-min heat response test (HRT) walking at 60% $\dot {\rm V}$ V ˙ O2peak in 40°C and 30% relative humidity before and after summer (i.e. November 2022 and March 2023). During the HRT, gastro-intestinal temperature (Tgi), skin temperature (Tsk), heart rate, local sweat rate (LSR) and whole-body sweat loss (WBSL) were recorded. Carbon monoxide rebreathing and dual-energy X-ray absorptiometry scans determined resting hematological measures and body composition. Participants completed physical activity (PA) diaries and wore an accelerometer for two one-week periods (pre- and post-summer). Daytime wet-bulb globe temperature (WBGT) was calculated for each summer day. Data are presented as posterior mean and 90% credible intervals. Participants reported 7 ± 4 h·wk−1 of outdoor PA, and daytime WBGT was 21.2 ± 4.6°C. Following summer, resting Tgi and heart rate were reduced by 0.2°C [−0.3, −0.1; probability of direction = 99%] and 7 beats·min−1 [−10, −3; 100%], respectively. During the HRT, there was an earlier onset of sweating (−0.2°C [−0.3, −0.0; 98%]), an attenuated rise of Tgi (0.2°C [−0.5, 0.0; 92%]) and mean Tsk changed by −0.2°C [−0.5, 0.1; 86%]. There was minimal evidence for heat adaptations in LSR or WBSL, hematological parameters or perceptual measures. This is the first study to demonstrate seasonal heat adaptations in active adolescents. Reductions in resting Tgi and exercising Tsk and a lower Tgi at the onset of sweating were associated with a smaller rise in Tgi during the HRT following summer. [ABSTRACT FROM AUTHOR]

Background and Purpose: The mechanistic target of rapamycin (mTOR) signalling pathway is a key regulator of cell growth and metabolism. Its deregulation is implicated in several diseases. The macrolide rapamycin, a specific inhibitor of mTOR, has immunosuppressive, anti‐inflammatory and antiproliferative properties. Recently, we identified tacrolimus, another macrolide immunosuppressant, as a novel activator of TRPM8 ion channels, involved in cold temperature sensing, thermoregulation, tearing and cold pain. We hypothesized that rapamycin may also have agonist activity on TRPM8 channels. Experimental Approach: Using calcium imaging and electrophysiology in transfected HEK293 cells and wildtype or Trpm8 KO mouse DRG neurons, we characterized rapamycin's effects on TRPM8 channels. We also examined the effects of rapamycin on tearing in mice. Key Results: Micromolar concentrations of rapamycin activated rat and mouse TRPM8 channels directly and potentiated cold‐evoked responses, effects also observed in human TRPM8 channels. In cultured mouse DRG neurons, rapamycin increased intracellular calcium levels almost exclusively in cold‐sensitive neurons. Responses were markedly decreased in Trpm8 KO mice or by TRPM8 channel antagonists. Cutaneous cold thermoreceptor endings were also activated by rapamycin. Topical application of rapamycin to the eye surface evokes tearing in mice by a TRPM8‐dependent mechanism. Conclusion and Implications: These results identify TRPM8 cationic channels in sensory neurons as novel molecular targets of the immunosuppressant rapamycin. These findings may help explain some of its therapeutic effects after topical application to the skin and the eye surface. Moreover, rapamycin could be used as an experimental tool in the clinic to explore cold thermoreceptors. [ABSTRACT FROM AUTHOR]

Background: Energy expenditure may be difficult to assess when hiking difficult trails. Case presentation: We measured physical activity exercise energy expenditure (PAEE) directly from oxygen uptake using a mobile device (cardiopulmonary exercise testing, CPET), and by using a formula based on heart rate (HR), or metabolic equivalent values from the Compendium of Physical Activity, and other physiological outcomes. Outcomes and implications: Total PAEE (1342 kcal) using CPET showed a two-fold difference between ascending and descending (887 vs. 455 kcal) during a 124-min hike. For HR, PAEE was 1893kcal (+551 kcal overreporting), while compendium-based scenarios ranged from 1179 to 1446 kcal, which was in closer range (−163 to +104 kcal/min) compared to the CPET data. Fluid consumption was 1300 mL/hour, with 1.1% bodyweight loss, peak skin temperature of 35.2°C and core body temperature of 39.2°C. Recommendations: Tables reasonably predict energy expenditure while not precisely reflecting the actual situation. [ABSTRACT FROM AUTHOR]