ABSTRACT Rising ambient temperatures increase health risks for outdoor workers; however, exertional heat exhaustion (EHE) among golf course workers remains underexplored. This study aimed to identify organizational, environmental, and personal factors associated with EHE-related symptoms. We conducted a retrospective case–control study of outdoor workers at 491 golf clubs in the Kanto region of Japan during the summer of 2025. Multivariate logistic regression identified independent risk and protective factors among 388 respondents, of whom 63.7% reported symptoms. Significant risk factors included high work intensity (adjusted odds ratio [AOR]: 4.40; p = 0.006), high humidity (AOR: 2.94; p = 0.012), and insufficient airflow (AOR: 2.03; p = 0.004). Protective factors included employer-provided heat education (AOR: 0.56; p = 0.025), sleep duration ≥6 h (AOR: 0.49; p = 0.001), and awareness of heat countermeasures (AOR: 0.42; p = 0.019). Scheduled breaks (AOR: 0.33; p = 0.008) and cooled break areas (AOR: 0.23; p < 0.001) were strongly associated with reduced risk, whereas shaded areas showed no significant association. Sunlight-shielding clothing (AOR: 0.52; p = 0.001) and cooling vests (AOR: 0.55; p = 0.018) were also protective. Effective risk reduction requires an integrated approach that combines workload moderation with functional apparel. This study provides the first quantitative evidence that organizational measures such as scheduled breaks and cooled break areas serve as effective protective factors in this occupational setting. Because key determinants often lie beyond individual control, proactive employer engagement and structural support are essential for ensuring worker safety.

ABSTRACT Exertional heat stroke (EHS) and Malignant Hyperthermia (MH) are potentially life-threatening conditions with overlapping clinical characteristics. In this study, we compared the thermoregulatory response to exercise under increased environmental temperatures in individuals with a history of EHS (n = 15) or MH (n = 14) to healthy controls (n = 15). Groups were age- and sex-matched (31 male, 13 female, 42 ± 10 years). A 60-min exercise test was performed on a cycle ergometer at an ambient temperature of 30.3 ± 0.6°C and a relative humidity of 33.5 ± 4.7%. A stepwise incremental exercise protocol was used to reach a metabolic heat production of 6, 8 and 9 W/kg body mass. Gastrointestinal (Tgi) and skin (Tsk) temperature were monitored continuously, and partitional calorimetry was used to calculate dry (Hdry) and respiratory heat loss (Hresp). Whole-body sweat rate (WBSR) was assessed by measuring body mass. Exercise-induced increases in Tgi (1.4 ± 0.5°C) and Tsk (1.9 ± 0.8°C) were observed, but the magnitude of increase across groups was comparable (ptime*group = 0.80 and p = 0.57, respectively). Hdry was significantly lower in EHS participants (54 ± 4 W) compared to controls (65 ± 11 W, p = 0.023). No differences were observed in Hresp and WBSR. Our results suggest that individuals with MH or a history of EHS do not have an altered thermoregulatory response to exercise in the heat in a controlled setting. Further research is required to determine to what extent the complex accumulation of risk factors contributes to EHS susceptibility.

ABSTRACT We determined whether the time of day when students exercise in a tropical climate and the environmental conditions in which they attend theory classes (air conditioning vs. tropical climate) have an impact on athletic performance and physiological, psychological and perceptual parameters. Twenty-nine students took part in four experimental sessions consisting of outdoor exercises and theory classes from 7am-1pm, according to a randomized and counterbalanced order. Cognitive and exercise performances, perceptual responses, core temperature and heart rate were assessed in the air-conditioned and tropical climate conditions. Cognitive performance was lower in the tropical vs air-conditioned environment, including lower concentration, higher inattention and lower processing speed during the theory classes. During theory classes in a tropical climate, heart rate and core temperature were higher. Average concentration scores (i.e. mean: 107.0 vs. 234.0), and inattention (i.e. mean: 96.0 vs. 32.5) at end-morning (i.e. 11am-1pm) were negatively affected by tropical climate compared to air conditioning when it was preceded by physical exercise at 9am-11am, but not at 7am-9am. There was a momentary sensation of fatigue, with higher scores at 11am-1 pm than at 7am-9am, in both conditions. Core temperatures were higher during exercise performance at 9am-11 am (38.6°C ±4.9°C) than at 7am-9 am (38.3°C ±5.2°C), but there was no difference for exercise performance, heart rate. Climate conditions must be taken into account for (i) cognitive performance and physiological parameters in tropical climate, and (ii) the time of day for exercise when theory classes take place in late morning and young student-athletes must perform cognitively well.

ABSTRACT The optimal Whole-body cryostimulation (WBC) exposure duration to reach the target skin temperature may vary depending on individual factors such as age, sex, and body mass index (BMI). Maintaining skin temperatures below 13.6°C is necessary to trigger significant cold-induced analgesia. The aim of our study is to investigate how these variables influence the duration required to reach the analgesic threshold temperature of 13.6°C during WBC. A randomized cross-over controlled trial was conducted with 90 healthy participants, categorized by age, sex, and BMI. Each participant underwent two sessions: a 4 min WBC exposure at −50°C and a control session. Skin temperature was measured using a thermal imaging camera before, during and after cold exposure. Significant differences in skin temperature were observed between groups. Among young participants, normal-weight men required 4 minutes of exposure to reach the analgesic threshold (p < 0.05), while normal-weight women reached it in 3 minutes (p < 0.01). Overweight young men needed 3 minutes and 30 seconds (p < 0.001), whereas overweight young women reached the threshold earlier, at 2 min and 30 s (p < 0.01). For senior participants, both normal-weight men and women reached the analgesic threshold at 3 minutes of exposure (p < 0.001). In contrast, overweight senior men and women needed only 2 minutes and 30 seconds to reach the target skin temperature (p < 0.01). The optimal WBC exposure duration for achieving analgesic effects varies significantly depending on individual characteristics, suggesting that WBC protocols should be tailored to maximize therapeutic benefits.

ABSTRACT The effects of exposure to extreme heat and cold temperatures on human health have mostly been studied in high-income countries. We examined this association by exploring the effect of extreme temperatures on mortality due to heatstroke and exposure to cold in India and by states. We used temperature data from the Indian Meteorological Department (IMD) and mortality data from the National Crime Records Bureau (NCRB) to examine trends in overall, gender, and age-specific mortality. We used structural breaks analysis to observe changes in India’s mortality trends during 2001–2019. We examined the time trends in the relationship between extreme temperature and mortality for 24 Indian states from 2001 to 2014. We used panel regression and spline regression models. Between 2001 and 2019, India reported 19,693 and 15,197 deaths due to heatstroke and cold exposure, respectively. Top three states with the greatest number of deaths due to heatstroke were Andhra Pradesh, Uttar Pradesh, and Punjab; for cold exposure it was Uttar Pradesh, Punjab, and Bihar. Working-age men were significantly more susceptible to heatstroke. Spline regression results indicated that mortality varied across different temperature bins for both extreme summer and winter temperatures. Our findings demonstrate an urgent need to strengthen welfare and social support systems and invest in built environment and livelihood interventions to counter the avoidable mortality from extreme temperature events.

ABSTRACT Cardiovascular disease is more prevalent in individuals of Black-African (BA) and South-Asian (SA) descent than White-European (WE) counterparts, with vascular dysfunction identified as contributing to this disparity. Chronic heat therapy can elicit positive vascular adaptations, potentially underpinned by the repeated cardiovascular strain experienced during acute heat exposures. This study examined the cutaneous peripheral microvascular responses following acute hot (HWI) and thermoneutral (CON) water immersion between males of WE, BA, and SA descent. Thirty-one young, healthy WE (n = 10), BA (n = 10), SA (n = 11) males completed 60 minutes of HWI (39°C) and CON (36°C) with thermoregulatory, cardiovascular, and perceptual responses measured throughout. Following 60 minutes of thermoneutral rest, forearm and Great toe cutaneous vascular conductance (CVC) were recorded during cutaneous post-occlusive reactive hyperemia (PORH) and local heating (LH). Baseline CVC was similar between groups (p ≥ 0.08). During PORH, BA had lower peak forearm and Great toe CVC than WE and SA, and a reduced CVC area under the curve compared to WE (p ≤ 0.01). Furthermore, BA Great toe CVC was blunted compared to WE and SA during both 42°C (p ≤ 0.033) and 44°C (p ≤ 0.02) LH, respectively. Great toe CVC was acutely increased following HWI in responses to 44°C LH compared to CON (p ≤ 0.039), with no race × condition interaction effects. In conclusion, despite blunted microvascular responses in BA, acute HWI did not elicit distinct effects between males of WE, BA, and SA descent, although microvascular responses to LH were greater following HWI.

Why is extreme heat associated with greater cardiovascular risk?: Comment on: Barry H, Iglesies-Grau J, Chaseling GK, Paul J, Gosselin C, D'Oliviera-sousa C, Juneau M, Harel F, Kaiser D, Pelletier-galarneau M, Gagnon D. The effect of heat exposure on myocardial blood flow and cardiovascular function. Ann Intern Med. 2024 Jul;177(7):901-910. doi: 10.7326/M24-3504