Effects of Medications on Heat Loss Capacity in Chronic Disease Patients: Health Implications Amidst Global Warming.

Pharmacological agents used to treat or manage diseases can modify the level of heat strain experienced by chronically ill and elderly patients via different mechanistic pathways. Human thermoregulation is a crucial homeostatic process that maintains body temperature within a narrow range during heat stress through dry (i.e., increasing skin blood flow) and evaporative (i.e., sweating) heat loss, as well as active inhibition of thermogenesis, which is crucial to avoid overheating. Medications can independently and synergistically interact with aging and chronic disease to alter homeostatic responses to rising body temperature during heat stress. This review focuses on the physiologic changes, with specific emphasis on thermolytic processes, associated with medication use during heat stress. The review begins by providing readers with a background of the global chronic disease burden. Human thermoregulation and aging effects are then summarized to give an understanding of the unique physiologic changes faced by older adults. The effects of common chronic diseases on temperature regulation are outlined in the main sections. Physiologic impacts of common medications used to treat these diseases are reviewed in detail, with emphasis on the mechanisms by which these medications alter thermolysis during heat stress. The review concludes by providing perspectives on the need to understand the effects of medication use in hot environments, as well as a summary table of all clinical considerations and research needs of the medications included in this review. SIGNIFICANCE STATEMENT: Long-term medications modulate thermoregulatory function, resulting in excess physiological strain and predisposing patients to adverse health outcomes during prolonged exposures to extreme heat during rest and physical work (e.g., exercise). Understanding the medication-specific mechanisms of altered thermoregulation has importance in both clinical and research settings, paving the way for work toward refining current medication prescription recommendations and formulating mitigation strategies for adverse drug effects in the heat in chronically ill patients.

Poor personal protective equipment practices were associated with heat-related symptoms among Asian healthcare workers: a large-scale multi-national questionnaire survey.

BACKGROUND: It is pertinent to understand the perceptions of healthcare workers (HCWs) with their associated personal protective equipment (PPE) usage and heat strain symptoms experienced to effectively combat the negative effects of heat stress during treatment and care activities. METHODS: We evaluated the associated heat stress perceived by HCWs across Asia and validated a questionnaire on perceptions of heat stress, associated PPE usage, and heat strain symptoms experienced. The questionnaire was administered to 3,082 HCWs in six Asian regions. Factor analyses, including Cronbach's alpha, assessed the questionnaire's validity and reliability. Structural equation modelling analysed the effects of knowledge, attitudes and practices, and heat strain symptoms. RESULTS: The questionnaire was found to be reliable in assessing HCWs' knowledge, and attitudes and practices towards heat stress and PPE usage (both Cronbach's alpha = 0.9), but not heat strain symptoms (Cronbach's alpha = 0.6). Despite knowledge of heat stress, HCWs had negative attitudes and practices regarding PPE usage (ß1 = 0.6, p < 0.001). Knowledge (path coefficient = 0.2, p < 0.001), and negative attitudes and practices (path coefficient = 0.2, p < 0.001) of HCWs towards heat stress and PPE usage adversely affected symptoms experienced. CONCLUSIONS: The questionnaire was not reliable in assessing symptoms. HCWs should, nevertheless, still self-assess their symptoms for early detection of heat strain. To effectively attenuate heat strain, understanding HCWs' attitudes and practices towards PPE usage should guide policymakers in implementing targeted heat management strategies.

Stochastic Exceptional Points for Noise-Assisted Sensing.

Noise is a fundamental challenge for sensors deployed in daily environments for ambient sensing, health monitoring, and wireless networking. Current strategies for noise mitigation rely primarily on reducing or removing noise. Here, we introduce stochastic exceptional points and show the utility to reverse the detrimental effect of noise. The stochastic process theory illustrates that the stochastic exceptional points manifest as fluctuating sensory thresholds that give rise to stochastic resonance, a counterintuitive phenomenon in which the added noise increases the system's ability to detect weak signals. Demonstrations using a wearable wireless sensor show that the stochastic exceptional points lead to more accurate tracking of a person's vital signs during exercise. Our results may lead to a distinct class of sensors that overcome and are enhanced by ambient noise for applications ranging from healthcare to the internet of things.

Impact of heat on all-cause and cause-specific mortality: A multi-city study in Texas.

BACKGROUND: Studies on the health effects of heat are particularly limited in Texas, a U.S. state in the top 10 highest number of annual heat-related deaths per capita from 2018 to 2020. This study assessed the effects of heat on all-cause and cause-specific mortality in 12 metropolitan statistical areas (MSAs) across Texas from 1990 to 2011. METHODS: First, we determined the heat thresholds for each MSA above which the relation between temperature and mortality is linear. We then conducted a distributed lag non-linear model for each MSA, followed by a random effects meta-analysis to estimate the pooled effects for all MSAs. We repeated this process for each mortality cause and age group to achieve the effect estimates. RESULTS: We found a 1 °C temperature increase above the heat threshold is associated with an increase in the relative risk of all-cause mortality of 0.60% (95%CI [0.39%, 0.82%]) and 1.10% (95%CI [0.65%, 1.56%]) for adults older than 75. For each MSA, the relative risk of mortality for a 1 °C temperature increase above the heat threshold ranges from 0.10% (95%CI [0.09%, 0.10%]) to 1.29% (95%CI [1.26%, 1.32%]). Moreover, elevated temperatures showed a slight decrease in cardiovascular mortality (0.37%, 95%CI [-0.35%, 1.09%]) and respiratory disease (1.97%, 95%CI [-0.11%, 4.08%]), however this effect was not considered statistically significant.. CONCLUSION: Our study found that high temperatures can significantly impact all-cause mortality in Texas, and effect estimates differ by MSA, age group, and cause of death. Our findings generate critical information on the impact of heat on mortality in Texas, providing insights for policymakers on resource allocation and strategic intervention to reduce heat-related health effects.

Effect of ice slurry ingestion on thermoregulatory responses during fixed-intensity cycling in humid and dry heat.

PURPOSE: This study examined the thermoregulatory response and ergogenic effects of ice slurry (ICE) ingestion in hot environments with high and low relative humidity (RH). METHODS: Eight males completed four trials in a crossover manner in dry (DRY: 34.7 ± 0.2 °C, 38 ± 2%RH) and humid heat (HUM: 34.8 °C ± 0.2 °C, 80 ± 1%RH). They ingested 8.0 g·kg-1 of ICE (0.0 °C) or 37.5 °C water (CON) during 30 min before exercise, and three aliquots (3.2 g·kg-1) of ICE or CON during 45-min cycling at 50%[Formula: see text]O2peak, followed by cycling to exhaustion at 80%[Formula: see text]O2peak (TTE). Body core temperature (Tcore), mean skin temperature (Tsk), heart rate (HR), thermal comfort, thermal sensation and rating of perceived exertion (RPE) were measured. RESULTS: Relative to CON, ICE improved TTE by 76.5 ± 96.5% in HUM and 21.3 ± 44.9% in DRY (p = 0.044). End-exercise Tcore was lower in ICE versus CON in DRY (37.8 ± 0.4 °C versus 38.1 ± 0.3 °C, p = 0.005) and HUM (38.8 ± 0.4 °C versus 39.3 ± 0.6 °C, p = 0.004). ICE decreased HR, heat storage and heat strain index only in DRY (p < 0.001-0.018). ICE improved thermal sensation and comfort in DRY and HUM (p < 0.001-0.011), attenuated RPE in HUM (p = 0.012) but not in DRY (p = 0.065). CONCLUSION: ICE tended to benefit performance in humid heat more than in dry heat. This is likely due to the reduced extent of hyperthermia in dry heat and the relative importance of sensory inputs in mediating exercise capacity.

Thermal perception and lung function: a panel study in young adults with exercise under high outdoor temperature.

It has been observed that high temperature exposure is associated with a reduction in lung function and some possible biological mechanisms have been suggested. However, it is unclear if thermal perception plays a role in the association. From September 3rd to 15th, 2018, in Guangzhou, China, we repeatedly measured daily thermal perception and lung function among 126 participants with outdoor military training. We performed a linear mixed model and stratified analyses by the origin of students, gender, and the training period to evaluate the effects of thermal perception on lung function. A total of 399 measurements were collected. Per vote increase in thermal sensation vote towards the "hot" direction was associated with a - 0.04 L (95% CI: - 0.08 to - 0.01) decrease in forced vital capacity (FVC), and - 0.04 L (95% CI: - 0.08 to - 0.01) decrease in forced expiratory volume in 1 s (FEV1). Per grade increase towards the "very uncomfortable" direction for thermal comfort vote was associated with an increased percentage of forced expiratory volume in 1 s (FEV1%) by 1.52% (95% CI: 0.18 to 2.86). For thermal preference, with preferred cooler vote increased by one level, FVC and FEV1 decreased by - 0.05 L/s (95% CI: - 0.08 to - 0.02) and - 0.05L/s (95% CI: - 0.08 to - 0.02), respectively. The effects of thermal perception on lung function were stronger among non-local and in the first week of training. Our study suggests that in the same high-temperature environment, thermal perception is associated with lung function, even in healthy adults.

Practical internal and external cooling methods do not influence rapid recovery from simulated taekwondo performance.

Background/Objectives: The influence of post-exercise cooling on recovery has gained much attention in the empirical literature, however, data is limited in regards to optimizing recovery from taekwondo performance when combat is repeated in quick succession within the same day. The aim of this study was therefore to compare the effects of external and internal cooling after simulated taekwondo combat upon intestinal temperature (Tint), psychomotor skills (reaction time, response time, movement time), and neuromuscular function (peak torque, average power, time to reach peak torque). Methods: Using a randomized counterbalanced crossover design, 10 well-trained male taekwondo athletes completed four recovery methods on separate occasions: passive recovery (CON), a 5-minute thermoneutral water immersion (35°C) (TWI), a 5-min cold water immersion (15°C) (CWI), and ice slurry ingestion (-1°C) (ICE; consumed every 5 min for 30 min). Heart rate (HR), blood lactate (Blac) concentrations, and Tint were determined at rest, immediately after combat, and at selected intervals during a 90-min recovery period. Neuromuscular functional (measured with isokinetic dynamometer) and psychomotor indices were assessed at baseline and after the recovery period. Results: ICE led to a significantly lower Tint at 30 min (P<0.01) and 45 min (P<0.01) after simulated combat; 15-30 min after cessation of ingesting ice slurry, compared with the CON and TWI conditions, respectively. However, there were no differences in Tint across time points between the other conditions (P>0.05). Psychomotor skills and neuromuscular function indices returned to baseline values after the 90 min recovery period (P>0.05) with no differences observed between conditions (P>0.05). Conclusion: The present findings suggest that internal (ICE) and external (CWI) recovery methods appear to have little impact on physiological and functional indices over the time course required to influence repeated taekwondo combat performance.

Evaluating the effectiveness of labor protection policy on occupational injuries caused by extreme heat in a large subtropical city of China.

On March 1, 2012, the Chinese government implemented the Administrative Measures on Heatstroke Prevention (AMHP2012) to combat the occupational health impacts of extreme heat, and reducing occupational injury was one of the main purposes. This study aimed at quantifying the intervention effects of the AMHP2012 on extreme heat-related occupational injuries and subsequent insurance payouts in Guangzhou, China. Data on occupational injuries and insurance payouts were collected from March 1, 2011, to February 28, 2013, from the occupational injury insurance system of Guangzhou. A quasi-experimental design with before-after control was adopted. Interrupted time series analysis was performed to quantify the change of occupational injuries and insurance payouts after policy implementation. The distributed lag non-linear model was used to explore whether injury claims and insurance payouts due to extreme heat decreased. A total of 9851 injury claims were included in the analysis. After policy implementation, the risk of occupational injuries and insurance payouts decreased by 13% (RR = 0.87, 95%CI: 0.75, 0.99) and 24% (RR = 0.76, 95% CI: 0.58, 0.94), respectively. The attributable fraction of extreme heat-related occupational injuries decreased from 3.17% (95%eCI: 1.35, 4.69) to 1.52% (95%eCI: -0.36, 3.15), which contributed to 0.86 million USD reduction of insurance payouts. Both males and females, low-educated, young and middle-aged workers, workers at small or medium-sized enterprises, engaging in manufacturing, and with both minor and severe injuries were apparently associated with decreased rates of extreme heat-related occupational injuries. The AMHP2012 policy contributed to the reduction of extreme heat-related occupational injuries and insurance payouts in Guangzhou, China, and this research provided novel evidence for decision-makers to better understand the necessity of implementing health protection policies among laborers under climate change.

Effects of Heat Exposure and Ice Slurry Ingestion on Risk-Taking Behavior in Healthcare Workers.

PURPOSE: Healthcare workers (HCWs) wearing personal protective equipment (PPE) experience physiological strain that can impair motor and psychological functions, potentially affecting patient care. We assessed the effects of heat exposure on maximal strength and risk-taking behavior among PPE-wearing HCWs and the efficacy of ice slurry to alleviate adverse effects. METHODS: Seventeen HCWS completed two experimental trials in a crossover design, consuming 5 g·kg -1 of body mass of ambient drink (AMB) or ice slurry (ICE) before donning PPE and undergoing 2 h of simulated decontamination exercise (wet-bulb globe temperature (WBGT): 25.9°C ± 0.8°C, PPE microenvironment WBGT: 29.1°C ± 2.1°C). Body core temperature ( Tc ), heart rate (HR), chest skin temperature ( Tsk ), ratings of perceived exertion (RPE), thermal sensation (RTS), maximal voluntary contraction (MVC), risk-taking behavior (balloon analogue risk-taking task (BART)), and salivary cortisol were assessed. RESULTS: Predrinking to postdrinking ∆ Tc was greater in ICE (-0.2°C ± 0.1°C) than AMB (-0.0°C ± 0.1°C, P = 0.003). Post-drinking RTS was lower in ICE (2.7 ± 1.2) than AMB (4.1 ± 0.4, P < 0.001). ICE and AMB had similar Tc and HR (both P > 0.05), but Tsk was lower in ICE than AMB ( P = 0.049). A lower MVC (30.3 ± 6.7 vs 27.4 ± 4.9 kg, P = 0.001) and higher BART-adjusted total pump count (472 ± 170 vs 615 ± 174 pumps, P = 0.017) was observed pretrial to posttrial in AMB but absent in ICE (both P > 0.05). Salivary cortisol was similar between trials ( P = 0.42). CONCLUSIONS: Heat-exposed PPE-wearing HCWs had impaired maximal strength and elevated risk-taking behavior. This may increase the risk of avoidable workplace accidents that can jeopardize HCWs and patient care. Ice slurry ingestion alleviated these heat-related impairments, suggesting its potential as an ergogenic aid.

A History of Heat Health Management Policies in the Singapore Military.

Our paper, which is the first historical study about heat injuries in Singapore, seeks to situate the Singapore Armed Forces' (SAF) history of heat stress management policies within the national context. Firstly, we observe that since the late 1970s, a research-driven approach has been adopted by the SAF's military medical leaders to formulate a range of policies to address the Forces' high incidence of heat injuries. This has resulted in the introduction of SAF-wide training measures, and the assembling of local scientific research expertise, which has led to a sharp reduction in heat injury incidence from the 1980s to 2000s. Through this, the SAF sought to demonstrate that its heat stress mitigation measures made the Singapore military 'heat proof'. Secondly, the state shaped a soldier safety agenda in the late 2000s on the back of an increasing emphasis on safety and the transformation of the SAF into a highly-educated and technologically-sophisticated force. This meant a shift towards concern about the welfare of every soldier, particularly through the state's drive to eradicate all training-related deaths. Accordingly, the SAF medical military leaders responded to the state's safety agenda by introducing heat stress management research and policies that were oriented towards the target of eradicating deaths due to heat stress. This policy and research direction, as such, has been strongly guided by the state's safety agenda and utilised to demonstrate to the public that all efforts have been taken to comprehensively mitigate the risks of heat.

Effect of ischemic preconditioning on maximum accumulated oxygen deficit in 400-meter runners.

The main aim of this study was to examine the influence of ischemic preconditioning (IPC) on maximal accumulated oxygen deficit (MAOD). We conducted a three-arm and assessor-blinded randomized, controlled crossover study. Sixteen 400-meter running male athletes (19.9 ± 1.3 years; 1.78 ± 0.05 m; 67.9 ± 5.5 kg) completed three supramaximal intensity tests separated with Control, Local (legs), and Remote (arms) IPC interventions. IPC was induced on the limbs on both sides (4×5 min alternating unilateral occlusion 220 mmHg and reperfusion; arms or thighs; right side first) before participants performed the supramaximal intensity test on a treadmill at 110% VO2max intensity to exhaustion. During each test, indices of respiratory gas exchange, blood lactate, and heart rate were determined. The MAOD was calculated as the difference between the theoretical VO2 demand and the actual VO2 during the supramaximal intensity test. Differences from three trials were analyzed using ANOVA with repeated measures. IPC increased MAOD (RIPC, 59 ± 17 ml/kg/min, p = 0.018; LIPC, 57 ± 15 ml/kg/min, p = 0.037; p < 0.05) compared with Control (49 ± 9 ml/kg/min). Time to exhaustion was enhanced after IPC (Control: 257.2 ± 69.5 s, RIPC, 292.3 ± 66.6 s, p = 0.048; LIPC, 291.6 ± 79.2 s, p = 0.042; p < 0.05). In contrast, the enhancements of RIPC and LIPC trials were similar (p = 1.000). Blood lactate concentrations were similar across the three intervention conditions (p > 0.05). Acute IPC improved MAOD and supramaximal intensity exercise capacity in 400-meter running athletes. The increased MAOD indicated greater anaerobic capacity, which can be the potential mediator for improvement in exhaustion time.HighlightsIschemic preconditioning may improve the exhaustion time of supramaximal intensity running in well-trained 400-meter middle distance athletes.Acute IPC may be beneficial to anaerobic exercise capacity as the maximal accumulated oxygen deficit increases after IPC.Acute IPC occlusion on the upper arms or thighs may improve anaerobic capacity.

Assessment of Changes in Physiological Markers in Different Body Fluids at Rest and after Exercise.

Physiological and biological markers in different body fluids are used to measure the body's physiological or pathological status. In the field of sports and exercise medicine, the use of these markers has recently become more popular for monitoring an athlete's training response and assessing the immediate or long-term effects of exercise. Although the effect of exercise on different physiological markers using various body fluids is well substantiated, no article has undertaken a review across multiple body fluids such as blood, saliva, urine and sweat. This narrative review aims to assess various physiological markers in blood, urine and saliva, at rest and after exercise and examines physiological marker levels obtained across similar studies, with a focus on the population and study methodology used. Literature searches were conducted using PRISMA guidelines for keywords such as exercise, physical activity, serum, sweat, urine, and biomarkers, resulting in an analysis of 15 studies for this review paper. When comparing the effects of exercise on physiological markers across different body fluids (blood, urine, and saliva), the changes detected were generally in the same direction. However, the extent of the change varied, potentially as a result of the type and duration of exercise, the sample population and subject numbers, fitness levels, and/or dietary intake. In addition, none of the studies used solely female participants; instead, including males only or both male and female subjects together. The results of some physiological markers are sex-dependent. Therefore, to better understand how the levels of these biomarkers change in relation to exercise and performance, the sex of the participants should also be taken into consideration.

Extreme temperature increases the risk of stillbirth in the third trimester of pregnancy.

Epidemiological studies have reported the association between extreme temperatures and adverse reproductive effects. However, the susceptible period of exposure during pregnancy remains unclear. This study aimed to assess the impact of extreme temperature on the stillbirth rate. We performed a time-series analysis to explore the associations between temperature and stillbirth with a distributed lag nonlinear model. A total of 22,769 stillbirths in Taiwan between 2009 and 2018 were enrolled. The mean stillbirth rate was 11.3 ± 1.4 per 1000 births. The relative risk of stillbirth due to exposure to extreme heat temperature (> 29 °C) was 1.18 (95% CI 1.11, 1.25). Pregnant women in the third trimester were most susceptible to the effects of extreme cold and heat temperatures. At lag of 0-3 months, the cumulative relative risk (CRR) of stillbirth for exposure to extreme heat temperature (29.8 °C, 97.5th percentile of temperature) relative to the optimal temperature (21 °C) was 2.49 (95% CI: 1.24, 5.03), and the CRR of stillbirth for exposure to extreme low temperature (16.5 °C, 1st percentile) was 1.29 (95% CI: 0.93, 1.80). The stillbirth rate in Taiwan is on the rise. Our findings inform public health interventions to manage the health impacts of climate change.

Cultural differences in hydration practices among physically active individuals: a narrative review.

It is well-established that appropriate hydration practices are essential in promoting health and optimizing performance and recovery. However, evidence-based hydration guidelines may not be adopted due to cultural differences across countries, such as religious beliefs, traditions, preferences, and beverage availability. Examples of hydration practices influenced by culture include beer consumption after sports in Western countries, consumption of sugarcane juice in India and Ramadan fasting among Muslims. For most cultural hydration practices, there is limited scientific evidence on their effects on rehydration, exercise performance, and recovery. Despite possible benefits of various hydration practices on exercise performance and recovery, they are inconsistent with current evidence-based hydration recommendations. More research on the impacts of cultural hydration differences on physiology, performance, and recovery is warranted to allow evidence-based guidelines and advisories. Abbreviations: ABV: alcohol by volume, ACSM: American College of Sports Medicine, NATA: National Athletic Trainers' Association, ROS: reactive oxygen species, TCM: Traditional Chinese Medicine.

Labour productivity and economic impacts of carbon mitigation: a modelling study and benefit-cost analysis.

BACKGROUND: Despite the emerging carbon neutrality pledges from different countries, it is still unclear how much these pledges would cost and how the costs would compare with the economic benefits. Comparisons at the country level are important for tightening country-specific emissions trajectories to keep the temperature limit targets outlined in the Paris Agreement within reach. We aimed to systematically estimate avoided heat-related labour productivity losses against the costs of climate change mitigation at country and regional levels. METHODS: In this modelling study, to address the above-mentioned research gaps, we first selected two representative climate change scenarios (Representative Concentration Pathway 6.0 [RCP6.0] scenario, a higher warming scenario representing limited mitigation pledges before the Paris Agreement with around 3°C warming by the end of this century; and RCP2.6 scenario, a lower warming scenario assuming global temperature rise is limited to 2°C) and estimated heat-related labour productivity loss using the exposure-response function at country and regional levels. By representing the direct heat-related labour productivity losses in a multiregional global computable general equilibrium model, we then did a benefit-cost analysis to quantify the economic benefits of avoided heat-related labour productivity losses as well as the estimated reduction in gross domestic product (GDP) related to carbon reduction. FINDINGS: By 2100, the overall economic losses due to heat-related labour productivity loss could range from about 1·5% of global GDP under the RCP6.0 scenario to about 0·1% of global GDP under the RCP2.6 scenario. The productivity losses will be highly concentrated in low-latitude regions, especially in southeast Asia, India, and the Middle East, implying the necessity of additional adaptation measures. By 2100, about 51·8% of global climate change mitigation costs could be offset by economic benefits from reduced labour productivity losses. Cumulatively, about 17·0% of climate change mitigation costs could be offset by the economic benefits between 2020 and 2100, when using a 2% social discounting rate. The costs and benefits of climate change mitigation will be distributed highly unevenly across regions due to their varying climate zones and economic structures. Regions with benefits from reduced productivity losses higher than mitigation costs are mainly low-latitude and tropical regions with lower income and lower emissions, such as southeast Asia, Brazil, and Mexico. More than half the climate change mitigation costs could be offset by the economic benefits by 2100 for the world's largest emitters, including the USA, China, the EU, and India. Low benefit-cost ratios are expected in economies that rely on fossil fuels, such as Canada, Russia, and the Middle East. INTERPRETATION: Although pledging carbon neutrality implies radical changes to most economies, substantial health and economic gains can be achieved by reduced heat-related labour productivity loss, even without accounting for other benefits. The benefit-cost analysis in this study shows the potential for choosing more stringent climate change mitigation pathways in some regions. Regions with low benefit-cost ratios need to restructure their economies to reduce mitigation costs as well as losses from declined fossil fuel exports. FUNDING: National Natural Science Foundation of China, Tsinghua-Toyota Joint Research Fund, the Wellcome Trust, Tsinghua University-China Three Gorges Corporation Joint Research Center for Climate Governance Mechanism and Green Low-carbon Transformation Strategy, the National Research Foundation, Prime Minister's Office, Singapore (Campus for Research Excellence and Technological Enterprise [CREATE] programme), and the Global Energy Interconnection Development and Coorperation Organization.

Efficacy of Isothermic Conditioning over Military-Based Heat Acclimatization and Interval Training in Tropical Native Males.

PURPOSE: We compared the effectiveness of three field-based training programs, namely military-based heat acclimatization (MHA), isothermic conditioning (IC) and interval training (IT), in inducing physiological adaptations in tropical natives. METHODS: Fifty-one untrained tropical native males (mean ± standard deviation: age, 25 ± 2 yr; body mass index, 23.6 ± 3.2 kg·m -2 ; body fat, 19% ± 5%; 2.4-km run time, 13.2 ± 0.9 min) donned the Full Battle Order attire (22 kg) and performed a treadmill route march heat stress test in an environmental chamber (dry bulb temperature, 29.9°C ± 0.5°C; relative humidity, 70% ± 3%). Heat stress tests were conducted before (PRE) and after (POST) a 2-wk training intervention consisting of either a MHA ( n = 17, 10 sessions of military-based heat acclimatization), IC ( n = 17, 10 sessions with target gastrointestinal temperature ( Tgi ) ≥ 38.5°C) or IT ( n = 17, six sessions of high-intensity interval training) program. Tgi , HR, mean weighted skin temperature ( Tsk ), physiological strain index (PSI) and thigh-predicted sweat sodium concentration ([Na + ]) were measured and analyzed by one-factor and two-factor mixed design ANOVA with a 0.05 level of significance. RESULTS: Field-based IC induced a greater thermal stimulus than MHA ( P = 0.029) and IT ( P < 0.001) during training. Reductions in mean exercise Tgi (-0.2°C [-0.3°C, 0.0°C]; P = 0.009) , PSI (-0.4 [-0.7, -0.1]; P = 0.015) and thigh-predicted sweat [Na + ] (-9 [-13, -5 mmol·L -1 ]; P < 0.001) were observed in IC but not MHA and IT (all P > 0.05). Resting HR (MHA, -4 bpm [-7, 0 bpm]; P = 0.025; IC, -7 bpm [-10, -4 bpm]; P < 0.001; IT, -4 bpm [-8, -1 bpm]; P = 0.008) and mean exercise HR (MHA, -4 [-8, 0 bpm]; P = 0.034; IC, -11 bpm [-15, -8 bpm]; P < 0.001, IT = -5 bpm [-9, -1 bpm]; P = 0.012) were lowered in all groups after training. Isothermic conditioning elicited a greater attenuation in mean exercise HR and thigh-predicted sweat [Na + ] relative to MHA (both P < 0.05). No between-group differences were observed when comparing MHA and IT (all P > 0.05). CONCLUSIONS: Isothermic conditioning induced a more complete heat-adapted phenotype relative to MHA and IT. Interval training may serve as a time efficient alternative to MHA.

The Impact of Temperature on the Risk of COVID-19: A Multinational Study.

The current understanding of ambient temperature and its link to the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unclear. The objective of this study was to explore the environmental and climatic risk factors for SARS-CoV-2. For this study, we analyzed the data at the beginning of the outbreak (from 20 January to 31 March 2020) to avoid the influence of preventive or control measures. We obtained the number of cases and deaths due to SARS-CoV-2, international tourism, population age, universal health coverage, regional factors, the SARS-CoV-2 testing rate, and population density of a country. A total of 154 countries were included in this study. There were high incidence rates and mortality risks in the countries that had an average ambient temperature between 0 and 10 °C. The adjusted incidence rate for temperatures between 0 and 10 °C was 2.91 (95% CI 2.87-2.95). We randomly divided the data into a training set (80% of data) for model derivation and a test set (20% of data) for validation. Using a random forest statistical model, the model had high accuracy for predicting the high epidemic status of a country (ROC = 95.5%, 95% CI 87.9-100.0%) in the test set. Population age, temperature, and international tourism were the most important factors affecting the risk of SARS-CoV-2 in a country. An understanding the determinants of the SARS-CoV-2 outbreak can help to design better strategies for disease control. This study highlights the need to consider thermal effect in the prevention of emerging infectious diseases.

Correction: Fan et al. Efficacy of Ingesting an Oral Rehydration Solution after Exercise on Fluid Balance and Endurance Performance. Nutrients 2020, 12, 3826.

The authors would like to make a correction in a recent published paper [...].

Reply to Dumke, C. Comment on "Fan et al. Efficacy of Ingesting an Oral Rehydration Solution after Exercise on Fluid Balance and Endurance Performance. Nutrients 2020, 12, 3826".

We would like to thank Dr. Charles Dumke for taking interest in our recent publication [...].

Assessment of dehydration using body mass changes of elite marathoners in the tropics.

OBJECTIVES: The ACSM recommends drinking to avoid loss of body mass >2% during exercise to avert compromised performance. Our study aimed to assess the level of dehydration in elite runners following a city marathon in a tropical environment. DESIGN: Prospective cohort design. METHODS: Twelve elite runners (6 males, 6 females; age 24-41 y) had body mass measured to the nearest 0.01kg in their race attire immediately before and after the 2017 Standard Chartered Singapore Marathon 2017. Body mass change was corrected for respiratory water loss, gas exchange, and sweat retained in clothing, and expressed as % of pre-race mass (i.e. % dehydration). RESULTS: Data are expressed as means±SD (range). Dry bulb temperature and humidity were 27.9±0.1°C (27.4-28.3°C) and 79±2% (73-82%). Finish time was 155±10min (143-172min). Male runners finishing positions ranged from 2-12 out of 7627 finishers, whilst female runners placed 1-8 out of 1754 finishers. Body mass change (loss) and % dehydration for all runners were 2.5±0.5kg (1.8-3.5kg) and 4.6±0.9% (3.6-6.8%). Male runners experienced body mass loss of 2.8±0.5kg and 4.9±1.2% while females experienced body mass loss of 2.1±0.2kg and 4.3±0.6%. CONCLUSIONS: Despite experiencing dehydration (4.6% body mass loss) two-fold higher than current fluid replacement guidelines recommend (≤2%), elite male and female runners performed successfully and without medical complication in a hot weather marathon.