Wet Bulb Globe Temperature Research Articles

Investigating Compound Drought and Hot Extreme Events in Southeast Asia Through Copula Analysis

ABSTRACTThe concurrent occurrences of drought and extreme heat events, such as heatwaves, present substantial threats to human health and ecosystems. This study delves into a thorough examination of the collective impacts of drought and extreme heat events in Southeast Asia (SEA) over the past 83 years (1941–2023). Two primary definitions guided the investigation: Compound Drought and Heatwave Events (CDHW) and Compound Hot Droughts (CHD). The Wet‐Bulb Globe Temperature (WBGT) was employed to define heatwaves and extreme hot events, while the Standardised Precipitation Evapotranspiration Index (SPEI) was used for drought definition. In addition, the study explored the impact of linear detrending on copula fitting, assessing its effects. The findings of the study consistently revealed a strong positive correlation between drought and heatwaves in CDHW. On the other hand, CHD exhibited varied correlation patterns across regions. Furthermore, the study highlighted that linear detrending had a lower sensitivity in CDHW compared to CHD. The analysis uncovered significant regional disparities in the joint return period ranking of compound events, stemming from diverse copula analysis approaches. Particularly in non‐continental SEA, notably in some regions like Sumatra Island, a noteworthy distinction between CDHW and CHD emerged, indicating the limited applicability of CHD in scenarios with stringent concurrence of compound events. These insights provide valuable assistance to the research community, aiding in the discernment of the distinctions between CDHW and CHD in drought and heat‐event assessment.

High levels of heat stress among sugarcane workers in Thailand.

With continued global warming, the effects of elevated temperatures on the health of agricultural workers are a particular concern. This study characterized the levels of heat stress in Thai sugarcane workers and investigated whether season and harvesting method were associated with it. Three hundred sugarcane workers in Nakhon Sawan Province, Thailand, were recruited, and information on demographics, working conditions, and clothing characteristics was collected from participants during the cooler months (n = 152 participants, mid-January to mid-February) and hotter month (n = 148, March). Heat stress was measured using the Wet Bulb Globe Temperature (WBGT) index, and the WBGT instruments were operated for a full work shift in the sugarcane fields where the participants worked. One-hour time weighted average (TWA) effective WBGT (WBGTeff-1hrTWA) estimates were determined for different times of the day based on the measured WBGT and clothing adjustment factor. The average WBGTeff-1hrTWA in the cooler months ranged from 22.5 °C during the early morning to 31.3 °C during the hottest time of the day, and for the hotter month, it ranged from 25.4 °C to 33.9 °C, respectively. The measured WBGT, natural wet-bulb temperature (Tnwb), dry-bulb temperature (Tdb), globe temperature (Tg), air velocity (Av), and absolute water vapor pressure (ea) were all statistically significantly higher in the hotter month than in the cooler months. Harvesting during the hotter month and harvesting burnt sugarcane were significantly associated with increased effective WBGT. The harvesters' heat stress in both seasons exceeded the American Conference of Governmental Industrial Hygienists - Threshold limit value for 72.7% of the working time in the cooler months and 90.9% in the hotter month. The heat stress in Thai sugarcane workers was high in both seasons, particularly in the hotter month and when harvesting burnt sugarcane. This results in a very high risk of developing heat-related health effects, and measures are needed to reduce heat stress. Heat stress in agricultural and other outdoor work in tropical climates is an immediate and growing problem.

Associations between injury occurrence and environmental temperatures in the Australian and German professional football leagues.

A cross-sectional analysis was performed to investigate associations between environmental temperatures and injury occurrence in two professional male football (soccer) leagues. Data from seven seasons of the German Bundesliga (2142 matches) and four seasons of the Australian A-League (470 matches) were included. Injuries were collated via media reports for the Bundesliga and via team staff reports in the A-League and comprised injury incidence, mechanisms (contact, noncontact), locations (e.g., ankle, knee, and thigh), and types (e.g., muscle and tendon, joint and ligament). Weather data included ambient air temperature (temperature or T) and wet bulb globe temperature (WBGT), which were collected from online sources retrospectively. Generalized linear mixed models were analyzed to examine associations between temperature or WBGT and injury occurrence for each league, respectively. Additionally, matches were grouped into categories of 5°C temperature steps to compare for injury occurrence. Results showed no relationship existed between either temperature or WBGT and any injury occurrence, mechanisms, locations or types for the Bundesliga (P > 0.10). A trend for an increase in injury occurrence in higher WBGT existed in the A-League (P = 0.05). Comparisons between 5°C temperature categories showed no significant differences for injury occurrence for either temperature or WBGT in either League (P > 0.05). Within the observed temperature ranges (-11.2 to 37.1°C T; -12.2 to 29.6°C WBGT) environmental temperature had no relationship with the rate or type of injury occurrence in professional football. Nevertheless, the number of matches at extreme heat within this study was limited and other factors (e.g., playing intensity, season stage, ground conditions) likely co-influence the relationship with injuries.

Environmental Heat Stress Detrimentally Affects Match Running Performance of Elite Soccer Teams Competing in the UEFA Champions League.

Modric, T, Clemente, FM, Versic, S, Chmura, P, Andrzejewski, M, Kryściak, J, and Sekulic, D. Environmental heat stress detrimentally affects match running performance of elite soccer teams competing in the UEFA Champions League. J Strength Cond Res 39(2): e142-e148, 2025-This study aimed to examine the effect of environmental heat stress (EHS), defined by wet-bulb globe temperature (WBGT), on match running performance (MRP) while controlling for match-related contextual factors. For this purpose, 2 approaches were implemented: (a) the MRP in heat stress nonrisking environment (NoEHS) (WBGT <22° C) and heat stress risking environment (EHSrisk) (WBGT ≥22° C) were compared and (b) changes in MRP according to the 1° C increase in WBGT were evaluated. Data on MRP were collected using an optical tracking system from all teams ( n = 32) in all UEFA Champions League matches ( n = 125) during the 2022-23 season. Metrics included total distance (TD), low-intensity (LIR), moderate-intensity (MIR), and high-intensity running (HIR) distances. Results indicated that less TD (108.84 vs. 110.71 km; Cohen's d [ d ] = 0.53), MIR (15.91 vs. 17.09 km; d = 0.85), and HIR (8.75 vs. 9.23 km; d = 0.46) were covered in matches played in EHSrisk compared with the NoEHS. Further investigation indicated that for every 1° C increase in WBGT, TD averagely decreased by 0.16 km ( d = -0.48), MIR by 0.13 km ( d = -1.09), and HIR by 0.06 km ( d = -0.69). These findings demonstrated decreased overall and intensive workload during the matches in EHSrisk, suggesting the detrimental effect of EHS on match volume and intensity in elite soccer. When EHS risk is anticipated, consideration of playing and recovery strategies should be implemented by coaches to achieve tactical goals while minimizing physical strain during a match.

Urban green spaces as regulators of thermal comfort for different age groups in the context of heat waves

ABSTRACT This study aims to bolster the resilience of cities in the face of heat wave disasters by considering climate regulation and residents’ thermal sensation. We chose a humid-hot climatic region for the experiment and used blend of objective climatic measurements and subjective questionnaires to analyze the thermal environment characteristics of different spatial forms of green spaces and the thermal sensation of people from different socio-demographic groups. The results demonstrate that (1) waterfront vegetation (semi-enclosed spaces) and mixed vegetation area (semi-open spaces) are the most effective in regulating urban microclimate effects and improving subjective thermal experience, (2) the subjective thermal sensation ranges reported by individuals consistently exceed the corresponding grading criteria under high heat pressure defined by the Wet Bulb Globe Temperature (WBGT), and (3) both elders (>65 years old) and children (<14 years old) exhibit weaker thermal sensitivity and a gentler response to temperature changes than people in other age groups. These results imply that green spaces with different structures and compositions have different effects on people’s thermal perception and people from different age groups respond heat waves differently. Consequently, it is necessary to implement real-time temperature monitoring in areas where these individuals gather, and to strengthen the early warning systems and guidance for their outdoor activities. These findings provide a reference for optimizing urban spatial forms and developing integrated ‘Heat-Health Action Plan’ in humid-hot regions around the world.

Prenatal exposure to heat and humidity and infant birth size in Ghana.

Previous studies - primarily in high income countries - have shown that high prenatal temperatures are associated with adverse birth outcomes. However, these studies are mostly focused on average exposure across the full gestational period or short-term exposure immediately prior to delivery and may miss important sensitive windows of exposure in utero. Further, nearly all use ambient air temperature data, which neglect physiologically important interactions between air temperature and humidity. The Ghana Randomized Air Pollution and Health Study (GRAPHS) recruited pregnant individuals from 2013 to 2015 from communities in the Kintampo North Municipality and Kintampo South District of Ghana. We estimated daily maximum shaded wet bulb globe temperature (WBGTmax) and heat index (HImax) during pregnancy and examined associations with birth weight, birth length, head circumference, and incidence of low birth weight, preterm birth, and small for gestational age. Using linear regression analyses, trimester average models identified that higher WBGTmax in the first trimester was associated with larger head circumference; second trimester was associated with shorter birth length, lower birth weight and higher odds of preterm birth, and third trimester was associated with shorter gestational age and larger head circumference. Time-varying analyses using distributed lag nonlinear models find that, compared to the median, lower WBGTmax and HImax (25th percentile) during the first half of pregnancy was associated with higher birth weight and longer birth length. Compared to the median, lower WBGTmax and HImax (25th percentile) in the second half of pregnancy was associated with smaller head circumference while higher wet bulb globe temperature (75th percentile) was associated with larger head circumference. Overall, our study identified that higher WBGTmax and HImax are associated with pregnancy duration and newborn size. Given the overall trend in our study area of rising temperatures, these data suggest that adaptation strategies are urgently needed to protect child health.

Investigating wet-bulb globe temperature on heat-related illness in general population for alerting heat exposure: A time-stratified case-crossover study

Investigating wet-bulb globe temperature on heat-related illness in general population for alerting heat exposure: A time-stratified case-crossover study

Extreme heat risk and the potential implications for the scheduling of football matches at the 2026 FIFA World Cup.

Climate change is making extreme heat events more frequent and intense. This negatively impacts many aspects of society, including organised sport. As the world's most watched sporting event, the FIFA World Cup commands particular attention around the threat of extreme heat. The 2022 tournament in Qatar was moved from summer to winter in response to this threat, and now attention turns to the 2026 tournament in North America with extreme heat risk across many of the 16 host locations. We examine this risk by modelling wet bulb globe temperature (WBGT) - a widely used measure of heat stress - for the host locations using hourly meteorological data for the period 2003-2022. Our results show that 14 out of 16 host locations exceed WBGTs of 28°C, with four (nine) exceeding this threshold more than half the time during afternoons across the mean (hottest year) of the 20 year record. This threshold is important as the level beyond which some football governing bodies recommend match delay or postponement. A climatically sound argument is therefore presented to reschedule kick-off times outside the hottest afternoon hours for the host locations with highest heat risk at which no indoor air conditioned environment exists - primarily Miami and Monterrey, but also Philadelphia, Kansas City, Boston and New York. This study highlights the need to carefully assess heat risk ahead of major sporting events to help inform any potential interventions needed in the scheduling of matches and competitions in a warming climate.

Influence of work intensity on acute kidney injury risk during simulated occupational heat stress.

Violation of the National Institute of Occupational Safety and Health (NIOSH) heat stress recommendations by exceeding the allowable wet bulb globe temperature (WBGT) for a given work intensity and work-rest ratio augments acute kidney injury (AKI) risk. Here we tested the hypothesis that exceeding the allowable work intensity at a given WBGT and work-rest ratio would also worsen AKI risk. Twelve healthy adults completed two NIOSH recommendation compliant trials and one noncompliant trial consisting of a 4 h (half workday) exposure. Work-rest ratio was fixed at 30 min of walking and 30 min of rest each hour. Work intensity (metabolic heat production) was prescribed as a function of WBGT- 412±51 W (27.3±0.3°C; high intensity compliant [Chigh]), 290±75 W (31.6±0.2°C; low intensity compliant [Clow]), and 410±61 W (31.7±0.2°C; high intensity noncompliant [NChigh]). AKI risk was quantified by the product of urinary insulin-like growth factor-binding protein 7 and tissue inhibitor of metalloproteinase 2 normalized to urine specific gravity ([IGFBP7•TIMP-2]USG). Peak core temperature was higher in NChigh trial (38.3±0.4°C) compared to the compliant trials (Chigh: 38.0±0.3°C; Clow: 37.8±0.4°C; p≤0.0095). [IGFBP7•TIMP-2]USG increased from pre- to immediately postexposure in all trials (time effect: p=0.0454) but the peak increase was not different between trials (Chigh: 0.89±1.7 [ng/mL]2/1000; Clow: 0.78±1.7 [ng/mL]2/1000; NChigh: 1.0±1.4 [ng/mL]2/1000; p=0.7811). Violating the NIOSH recommendations by exceeding either the allowable work intensity (i.e., NChigh versus Clow) or WBGT (i.e., NChigh versus Chigh) resulted in a modest elevation in peak core temperature but did not modify AKI risk.

Comparative analysis of land cover changes on outdoor thermal comfort in Doha, Dubai, Kuwait City, Manama, Muscat, and Riyadh

ABSTRACT Rapid urbanization in Gulf cities has driven significant land cover changes, influencing outdoor thermal comfort and land surface temperatures (LST). This study investigates land cover dynamics from 1998 to 2023 across six cities – Doha, Dubai, Kuwait City, Manama, Muscat, and Riyadh – using Landsat imagery to assess LST, Normalized Difference Vegetation Index (NDVI) and approximated wet-bulb globe temperature (AWGBT). Results reveal an increase in urban areas, with Manama and Kuwait City experiencing the largest expansions (47.50% and 47.02%). Vegetation patterns varied, with cities like Dubai and Riyadh showing consistent increases, while Doha stagnated from 2013 to 2023. LST ranged from 42°C to 55°C, with desert areas showing the highest temperatures. Built-up areas had LST comparable to desert land, highlighting a reverse urban heat island effect. Dubai’s LST decreased between 2013 and 2023 due to successful green initiatives, contrasting with rising temperatures in other cities. The mean LST difference between the desert and urban areas was 2.5°C, and vegetation displayed a cooling effect, with a 3.5°C difference between vegetated and desert areas. Thermal comfort maps aligned with LST data, showing increasing heat stress, particularly in Doha and Kuwait City, while Dubai maintained stable comfort levels. This study underscores the critical role of vegetation and sustainable urban planning in mitigating heat stress and enhancing outdoor thermal comfort across Gulf cities.

Effects of Environmental Conditions, Core Temperature, and Hydration Status on Women’s Soccer Performance

National Collegiate Athletics Association (NCAA) Division III athletes have restrictive rules on preseason practice timelines leading to questions about how performances are affected by environmental conditions during preseason practices. Purpose: The purpose was to determine how heat, humidity, core body temperature, hydration status, and reported sleep affected the performances of women’s Division III soccer players during preseason training. Methods: Ten female collegiate soccer players (age=19.5±1.43 years, mass=62.14±5.01 kg, height=167.78±7.65 cm) were recruited. Core temperature was collected every 10 minutes during practice via an ingestable thermistor. Before each training session, participants recorded the previous night's sleep quantity and quality via the Karolinska Sleep Diary (KSD). Internal and external loads were monitored via heart rate, training load session rate of perceived exertion (TL-sRPE), and Global Position System (GPS) metrics. WetBulb Globe Temperature (WBGT) was continuously recorded throughout each training session as well as participant total fluid consumption. Results: TL-RPE, Δbody mass (ΔBM), ΔWBGT and maximum HR (maxHR) explained approximately 53% of the variance in intensity (r=0.73, F4,82=23.506, P&lt;.001). Whereas sleep metrics, session duration, and average heart rate had no significant (p&gt;0.05) impact on intensity. Conclusion: The changes in exercise intensity observed were most associated with the perceived training load, body mass loss, heat indices, and maximum heart rate. These variables should be controlled to elicit the desired training outcome while keeping player safety at the forefront during preseason soccer.

Associations Between Match Running Performance and Environmental Temperatures in 4 Professional Football Leagues.

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

The assessment of change in human heat stress risk in Brazil projected by the CMIP6 models

Abstract Climate change in Brazil is expected to increase the occurrences of heat related conditions hazardous to human health. Thresholds in the environmental conditions leading to heat stress in humans are projected to be exceeded for long periods of the year across large parts of the country. We analyse future changes in the frequency of exceeding heat stress related thresholds during the hottest part of the day as measured by the Wet Bulb Globe Temperature (WBGT) and using the CMIP6 climate projections. Thresholds that require significant reduction in physical activity are estimated to be exceeded for most of northern Brazilian if the increase in global temperature reaches 2 °C. These exceedances are projected to occur for the hottest part of the day for at least four months of the year. Reducing global temperature rise to 1.5 °C would lessen the impact seen in the northern states. If the temperature rise exceeds 3 °C, then almost the entire country at some point in the year will have levels of WBGT that would pose a high risk to health for people undertaking physical activity. Furthermore, 8% of the population will be affected for almost half of the year. The states of Amazonas, Amapa, Acre, Maranhao, Para and Roraima are most prone to experiencing high levels of WBGT and will be the first to experience WBGT levels that are too high for intense physical activity for more than 9 months if global temperature reaches 3 °C. High levels of WBGT will have significant impact on workers in rural areas. Adaptive policies for the agricultural areas of Brazil will need to consider the impact of heat stress rendering large regions of the country unsuitable for outdoor work for large parts of the year. This will be true even at global warming levels of 2 °C for northern and central Brazil.

Climate change and occupational health and safety. Risk of injuries, productivity loss and the co-benefits perspective.

Climate change is a fundamental threat to human health and outdoor workers are one of the most vulnerable population subgroups. Increasing heat stress and heatwaves are directly associated with the health and safety of workers for a large spectrum of occupations. Heat stress negatively affects labour supply, productivity, and workability. The aims of this study are to estimate the risk of work-related injuries for extreme temperature outdoor exposure in Italy, to evaluate the loss in productivity and the associated insurance costs for supporting the co-benefits analysis of the adaptation measures. The relationship between air temperature and occupational injuries (in the period 2014-19) was evaluated using a time-series approach, by means of a specific over-dispersed Poisson generalized linear regression model, applied to compensation data. To assess the effect of temperature on workability, the wet bulb global temperature (WBGT) was estimated by different levels of humidity and vapor pressure. The costs of injuries have been estimated according to the potential consequences in terms of paid insurance premium and including all management and human resources costs. We estimated 25,632 (95%CI 22,353-28,862) occupational injuries in Italy attributed to heat (between 75° and 99° percentiles) in the period 2014-2019, which corresponds to an average of 4272 cases for year. A decrease in productivity of about 6.5% was estimated for workers engaged in physical activities requiring high metabolic rates for every unit degree increase in temperature between 19.6C° and 31.8C°. The overall compensation costs associated to extreme heat exposure have been estimated to more than 292 million euros between 2014 and 2019, almost equal to 49 million euros per year. Prevention measures and adaptation strategies for contrasting the occupational exposure to extreme temperatures can help contain both the risk of injury and, productivity loss, in a co-benefits perspective.

Thermal comfort perception among park users in Prague, Central Europe on hot summer days-A comparison of thermal indices.

The assessment of human perception of the thermal environment is becoming highly relevant in the context of global climate change and its impact on public health. In this study, we aimed to evaluate the suitability of the use of four frequently used thermal comfort indices (thermal indices)-Wet Bulb Global Temperature (WGBT), Heat Index (HI), Physiologically Equivalent Temperature (PET), and Universal Thermal Climate Index (UTCI)-to assess human thermal comfort perception in three large urban parks in Central Europe, using Prague, the capital of the Czech Republic, as a case study. We investigated the relationship between the four indices and the thermal perception of park visitors, while taking into account the effect of the sex, age, and activity of the respondents and the week-time and daytime of their visit (assessed parameters). Park visitors were interviewed during the summertime, while collecting meteorological data. The correlations were performed to explore the relationship between the thermal perception and the individual thermal indices, multivariate statistical methods were used to explain how well the variation in thermal perception can be explained by the assessed parameters. We found a significant association between all the indices and thermal perception; however, the relationship was the strongest with HI. While thermal perception was independent of sex and week-time, we found a significant effect of age, physical activity, and daytime of the visit. Nevertheless, the effects can largely be explained by thermal conditions. Based on the results, we conclude that all the investigated indices are suitable for use in studies of thermal comfort in parks in Central Europe in summertime, while HI seems the most suitable for architects and planners.

Exposure to high-temperature and high-humidity environments associated with cardiovascular mortality.

Aging populations are susceptible to climate change due to physiological factors and comorbidities. Most relevant studies reported the effect of temperature on cardiovascular disease (CVD)-related mortality in aging populations. However, the combined effects of temperature and humidity on CVD-related mortality remain unclear. Here we used the Global Burden of Disease (GBD) database to analyze CVD burden and its impact on the incidence of CVD in individuals exposed to high-temperature and high-humidity (HTH) environments. The prospective China Health and Retirement Longitudinal Study (CHARLS) cohort was used to further analyze the relationship between exposure to HTH environments and CVD mortality in middle-aged and elderly individuals. We found significant positive correlations between the estimated annual percentage change of CVD and age-standardized rate, wet bulb globe temperature, and Humidex worldwide. In the CHARLS, a higher CVD mortality rate was significantly associated with exposure to HTH environments (P < 0.01). Long-term HTH environment exposure increased the risk of an abnormal low-density lipoprotein cholesterol (LDL-C) level (hazard ratio [HR], 1.30-2.44) and abnormal total cholesterol (TC) level (HR, 1.21-2.13), but the impact on high-density lipoprotein cholesterol (HDL-C) level was unclear. The mortality risks of long-term exposure to HTH environments were increased for middle-aged and elderly individuals with abnormal LDL-C (HR = 0.84-3.57) and TC (HR = 0.78-2.41) levels. These findings suggest that exacerbated dyslipidemia caused by long-term HTH environment exposure may be a key risk factor for CVD-related mortality in middle-aged and elderly individuals and suggest research directions into the effects of HTH environments on human health.

Packing house climatizado com resfriadores evaporativos - parte 1: Exposição ocupacional ao calor

ABSTRACT Agribusiness workers are regularly exposed to high temperatures, even in covered environments such as packing houses. This study aimed to assess the effect of evaporative coolers on reducing occupational heat exposure for workers and consequently improving the thermal comfort of the selection and packaging areas in a table grape packing house. The evaluation was conducted as per the criteria of the Brazilian legislation, based on the Regulatory Norms (NR’s) 15 and 17 of the Department of Labor. The study was conducted during two climatic production periods, dry and rainy, with the evaporative coolers on and off. With the coolers on, the workers’ occupational exposure to heat was reduced without exceeding the wet bulb globe temperature index tolerance limit for the activities carried out according to the NR 15. However, it did not provide adequate thermal comfort indices according to NR 17. Under semiarid conditions, coolers rendered the environment thermally comfortable for local workers. To reduce the risks to workers’ health, it is suggested that they take breaks in case of discomfort from the heat and provide workers with water and mineral salts to replenish sweat loss.

Squash in Los Angeles: Heat Strain and Performance Considerations at the 2028 Olympic Games.

The Los Angeles 2028 Olympics will mark the debut of squash, a high-intensity sport characterized by repeated efforts, posing potential thermoregulatory challenges. The demanding nature of squash results in substantial metabolic heat production, with consequential heat strain exacerbated by the indoor environment of squash courts, where low to moderate evaporative potential limits effective cooling. Players often experience increased body-heat storage and thermal strain, with muscle cramps (an early warning sign of more severe heat-related illnesses) commonly observed during tournaments. Despite these challenges, there are limited data on the thermoregulatory responses of elite squash players during match play. We discuss the thermoregulatory challenges faced by squash players and highlight key areas for research. Additionally, practical guidelines are provided for practitioners preparing squash players for the Los Angeles 2028 Olympics. Preliminary findings from international squash tournaments reveal that elite players endure significant physiological strain, with core temperatures rising to 39.0 °C to 40.1 °C, despite matches being played in mild wet-bulb globe temperatures of 19.4 °C (0.9 °C). Sustained heart rates exceeding 90% of maximal heart rate further compound this thermal strain. However, research on how thermal strain affects squash-specific fitness, recovery, and stroke mechanics are lacking. Such information is crucial for evaluating the need and effectiveness of tailored mitigation strategies such as heat training/exposures and precooling and midcooling during warm-up and match play. Systematic research into the thermal demands of squash and their impact on fitness and skills is needed. These insights can inform evidence-based strategies to safeguard athlete well-being and optimize performance at Los Angeles 2028.

Risk for exertional heat illness among US army enlistees: climate indexes, intrinsic factors and their interactions.

To characterise intrinsic and extrinsic (climatic) risks for mild and severe exertional heat illness (EHI) among first-year army enlistees. We examined 337 786 soldiers who enlisted between 2012 and 2019. Survival models were used to predict incident EHI from intrinsic factors (demographics, healthcare utilisation, chronic conditions, body mass index (BMI), Army Physical Fitness Test (APFT), upper/lower respiratory tract infections (URTI and LRTI), skin and soft-tissue infections (SSTI), extrinsic factors (geographical region, daily mean Universal Thermal Climate Index (UTCI), wet bulb globe temperature (WBGT)) and interactions. There were 1390 cases of mild and 359 cases of severe EHI. Females had a higher risk for mild (adjusted OR (aOR) 1.78; 95% CI 1.57 to 2.02) but a lower risk for severe (aOR 0.61; 95% CI 0.38 to 0.87) EHI. Obesity was associated with severe EHI (aOR: 1.76; 95% CI 1.09 to 2.84) but not mild EHI (aOR: 1.03; 95% CI 0.76 to 1.39). URTI was associated with severe (aOR: 2.44; 95% CI 1.12 to 5.30) and mild (aOR 3.72, 95% CI 2.84 to 4.87) EHI, as were LRTI (severe, aOR: 11.40; 95% CI 6.09 to 21.32; mild, aOR 2.06; 95% CI 1.22 to 3.46), but not SSTI. UTCI outperformed WBGT in predicting EHI. Outside the Southern USA, EHI risk was elevated at lower UTCI. Associations varied over climate conditions and generally did not increase with climatic heat stress. Respiratory infections were associated with the highest risk for EHI in soldiers. Risk mitigation strategies may include monitoring prevention and recovery from respiratory infections. Female sex and obesity may have different associated risks over climate conditions.

Impact of irrigation on farmworkers’ heat stress in California differs by season and during the day and night

Farmworkers, the frontline workers of our food system, are often exposed to heat stress that is likely to increase in frequency and severity due to climate change. Irrigation can either alleviate or exacerbate heat stress, quantification of which is crucial in intensely irrigated agricultural lands such as the Imperial Valley in southern California. We investigate the impact of irrigation on wet bulb globe temperature (WBGT), a key indicator of heat exposure in humans, using a validated high-resolution Weather Research and Forecasting (WRF) regional climate model, during day and night and in different seasons. We find that irrigation reduces WBGT by 0.3–1.3 °C during the daytime in summer due to strong evaporative cooling. However, during the summer nights, irrigation increases WBGT by 0.4–1.3 °C, when a large increase in humidity sufficiently raises the wet-bulb temperature. Urban and fallow areas adjacent to cropped fields also experience increased heat stress due to moisture advection from irrigated areas. Our results can inform heat-related policies in agricultural regions of California and elsewhere.