Mean Wet Bulb Globe Temperature Research Articles

Relationship between heat stress exposure and some immunological parameters among foundry workers.

Occupational exposure to heat stress may lead to changes in blood cell count. The objective of this retrospective descriptive-analytical field study is to investigate the relationship between heat stress exposure and some immunological parameters among foundry workers. This study was carried out on 55 subjects of which, 35 were working in a foundry unit (exposed group) and 20 were working in a computer numerical control (CNC) machining unit (control group). The measurement method consisted of taking 10cc of the subjects' blood between 10am and 2pm and then performing the automated blood cell counting and enzyme-linked immunosorbent assay (ELISA) on the sample. Environmental parameters such as noise levels, lighting, and the wet-bulb globe temperature (WBGT) index were measured at the subjects' workstations. All measurements were made in the first half of the month of July. The mean WBGT index was 22.5 ± 2.16°C for the control group and 32.97 ± 3.22°C for the exposed group. The laboratory test results show a significant decrease in white blood cell count and lymphocyte levels and a significant increase in neutrophil levels and neutrophil to lymphocyte ratio in exposed group compared with control ones (P < 0.05). IgM levels decrease under heat stress, but we do not observe significant differences between IgG and IgA levels between two groups. A significant negative correlation was observed between white blood cell count, lymphocyte levels, and IgM concentration with WBGT index and significant positive correlation was observed between neutrophil and neutrophil to lymphocyte ratio with WBGT index. No significant correlation was observed between sound pressure levels and light intensity with studied immunological parameters. In conclusion, under heat stress conditions, leukocytes levels and immunoglobulin concentration may reduce and it may weaken and suppress the human immune system.

Core Temperature Response During the Marathon Portion of the Ironman World Championship (Kona-Hawaii).

The Ironman triathlon consists of a 3.8 km swim, 180 km bike, and 42.195 km run. Thermoregulation responses play an important role in performance optimization and injury prevention. Factors such as environmental conditions including heat and humidity, athlete training level, and race duration can affect thermoregulation. Hyperthermia occurs when the core temperature rises above 38.5°C. The present study aims to describe core temperature (Tcore) in top-level and well-trained age group triathletes during the marathon of Ironman World Championship 2014 in Kona-Hawaii under thermal stress conditions. Tcore of 15 triathletes (age: 36.11 ± 7.36 years, body mass: 71.14 ± 7.12 kg, height: 179 ± 0.04 cm, and fat %: 8.48 ± 0.85) who classified for the Ironman World Championship was measured by an ingestible pill telemetry system prior to competition, during the marathon and 60 min after finishing the race. Mean wet bulb globe temperature (WBGT) during the marathon was 24.66°C (range 22.44–28.50°C). Body mass index (BMI) and perceived exertion (Borg Scale and Visual Analog Scale-Pain) were collected before the race and 60 min after the event. Time variables were extracted from their official race time and split times. Finish time was 10: 06:56 ± 0:48:30. Tcore was initially 36.62 ± 0.17°C, increased at the end of the event (38.55 ± 0.64; p < 0.01) and remained elevated 60 min after the event (38.65 ± 0.41°C; p < 0.002). BMI significantly decreased after the event (22.85 ± 1.11 vs. 21.73 ± 1.36; p < 0.05), whereas both exercise perceived exertion [Borg Scale (10.2 ± 1.64 vs. 18.60 ± 1.67; p < 0.003)] and perceived muscle pain [VAS Pain (2.75 ± 1.59 vs. 9.08 ± 1.13; p < 0.001)] increased significantly after the event. Tcore during competition correlated negatively with position in age group (r − 0.949, p = 0.051), but not with race time (r = −0.817; p = 0.183). High-level age group triathletes competing under thermal stress conditions in the Kona Ironman reached a state of hyperthermia during the marathon. After 60 min of recovery the hyperthermia persisted. Strategies to aid post-event cooling and recovery should be considered to avoid the potentially dangerous adverse health effects of hyperthermia.

Assessment of Heat Stress Exposure among Construction Workers in the Hot Desert Climate of Saudi Arabia.

ObjectivesExcessive heat exposure poses significant risks to workers in hot climates. This study assessed the intensity and duration of heat stress exposure among workers performing residential construction in southeastern Saudi Arabia (SA) during the summer, June–September 2016. Objectives were to: identify work factors related to heat stress exposure; measure environmental heat exposure at the construction sites; assess the heat stress risk among workers using the wet bulb globe temperature (WBGT) index; and determine if temperature-humidity indices can be appropriate alternatives to WBGT for managing heat stress risk at the construction sites.MethodsWorksite walkthrough surveys and environmental monitoring were performed, indoors and outdoors, at 10 construction sites in Al-Ahsa Province. A heat stress exposure assessment was conducted according to the American Conference of Governmental Industrial Hygienists (ACGIH®) guidelines, which uses the WBGT index. WBGT measurements from two instruments were compared. Alternative heat stress indices were compared to the WBGT: the heat index (HI) and humidex (HD) index.ResultsConstruction workers were exposed to excessive heat stress, indoors and outdoors over a large part of the work day. Complying with a midday outdoor work ban (12–3 p.m.) was not effective in reducing heat stress risk. The highest intensity of exposure was outdoors from 9 a.m. to 12 p.m.; a period identified with the highest hourly mean WBGT values (31–33°C) and the least allowable working time according to ACGIH® guidelines. Comparison of the alternative indices showed that the HI is more reliable than the HD as a surrogate for the WBGT index in the climate studied.ConclusionThe extreme heat exposure represents a serious risk. The severity of heat stress and its impact are projected to increase due to climate change, emphasizing the need for immediate improvement of the current required protective measures and the development of occupational heat stress exposure guidelines in SA.

Global Heat Wave Hazard Considering Humidity Effects during the 21st Century.

Humidity is a significant factor contributing to heat stress, but without enough consideration in studies of quantifying heat hazard or heat risk assessment. Here, the simplified wet-bulb globe temperature (WBGT) considering joint effects of temperature and humidity was utilized as a heat index and the number of annual total heat wave days (HWDs) was employed to quantify heat hazard. In order to evaluate the humidity effects on heat waves, we quantified the difference in the number of HWDs over global land based on air temperature and WBGT. Spatial and temporal changes in surface air temperature, relative humidity, WBGT, and the difference in HWDs were analyzed using multi-model simulations for the reference period (1986–2005) and different greenhouse gas emission scenarios. Our analysis suggests that annual mean WBGT has been increasing since 1986, which is consistent with the rising trend in surface air temperature despite a slight decrease in relative humidity. Additionally, changes in annual mean WBGT are smaller and more spatially uniform than those in annual mean air temperature as a cancelation effect between temperature and water vapor. Results show that there is an underestimation of around 40–140 days in the number of HWDs per year in most regions within 15° latitude of the equator (the humid and warm tropics) during 2076–2095 without considering humidity effects. However, the estimation of HWDs has limited distinction between using WBGT and temperature alone in arid or cold regions.

Evaluation of Occupational Exposure to Heat Stress and Physiological Responses of Workers in the Rolling Industry

Background and Objective: Many indices are used to assess occupational heat stress at the work environments. The aim of this study was to evaluate heat stress using Wet Bulb Globe Temperature (WBGT) index and Discomfort Index (DI), and by measuring physiological responses in the workers of the rolling industry and comparing the appropriateness of these indices for measuring heat stress. Methods: This cross-sectional study was carried out on 90 healthy workers of a rolling industry in eastern Tehran in 2017. Physiological parameters of core body temperature (Tcr) and Heart Rate (HR) were measured during the working shift according to ISO9886 standard. At the same time, environmental variables such as the natural wet temperature (Tnw), dry temperature (Td) and globe temperature (Tg) were measured and recorded at the workstations. Then, the DI and the WBGT indices were calculated using the related formulae. Data were analyzed using SPSS v. 21, t-test and Pearson correlation coefficient. Results: The mean heat stress indices were significantly higher in working conditions than resting conditions, and there was a significant difference between the physiological parameters of Tcr and HR in resting and working conditions (P&lt;0.001). According to the screening criteria of DI, 43.3% of the workers were exposed to the moderate level and 56.7% to the severe level of heat stress. There was a significant difference between the mean WBGT and the Threshold limit values (t= 4.903, P&lt;0.001). Pearson correlation test showed that there was a significant and direct linear relationship between the WBGT and the physiological parameters of Tcr and HR (r=0.317, P=0.002; r=0.434, P&lt;0.001, respectively). The DI index had a significant and direct linear relationship with HR; (r=0.229, P=0.03). Conclusion: The results showed that WBGT is a more appropriate index for evaluating the heat stress of workers in the rolling industry. High heat stress levels at the workstations along with heavy physical activity are health risks for workers in this industry; therefore, interventions must be undertaken to reduce exposure.

Modeling the risk of heat illness among basic training populations within the DoD, 2010–2017

ObjectiveTo identify predictors of the risk of developing exertional heat illness (EHI) among basic training populations in the Department of Defense.IntroductionAlthough effective preventive measures for heat-related illness have been recommended and mandated for military personnel, there continues to be incident cases. In 2016, there were 401 incident cases of heat stroke and 2,135 incident cases of “other heat illness” among all active component service members. Current military guidelines utilize the wet bulb globe temperature (WBGT) index to measure heat risk, guiding work/rest and hydration practices. The WBGT requires calibrated instrumentation and is based on fixed cutoff values. We propose using readily available meteorological data inputs and EHI cases to identify and validate an EHI risk prediction model. Prior studies have found that combinations of WBGT and the previous day’s WBGT and relative humidity and temperature have predictive value for EHI.1 We build upon prior work by using generalized additive models (GAMs).MethodsA case-control study was conducted among active component service members from all basic training installations from January 1, 2010 to May 31, 2017. Incident cases of EHI were identified utilizing diagnosis codes extracted from inpatient and outpatient medical encounters and confirmed reportable medical events. An equal number of random controls, matched by installation, were selected. Mean weather data during daylight hours from the Air Force Weather Squadron were provided for the closest weather station to the installation during the same time period. A GAM was used due to the non-linear association between EHI and weather predictors, to develop models for the risk of incident EHI. Training (75% of data) and test (25% of data) datasets were generated for model training and model validation. Three hundred sets of training and test datasets were randomly generated. For each set, sensitivity and specificity for EHI prediction was calculated. Four models with different combinations of predictors were compared: model 1 contains month, day of week, and installation; model 2 contains WBGT, month, day of week, and installation; model 3 contains WBGT, previous day’s WBGT, month, day of week, and installation; and model 4 contains relative humidity, temperature, month, day of week, and installation. Each predictor was significantly associated with EHI. The mean differences in sensitivity and specificity between all models and model 1 were compared and 95% confidence intervals were generated by bootstrapping. GAMs were generated using the mgcv package and odds ratios were generated using the oddsratio package in R.ResultsThere were 5,258 incident cases of EHI from 2010-2017 among active component service members stationed at basic training installations. There was not a significant difference in model performance when comparing the four models. The mean differences in sensitivity and specificity of each model compared to model 1 are displayed in Table 1. The association between log odds of EHI and WBGT, controlling for month, day of week, and installation (model 2) is displayed in Figure 1. There is not a single representative odds ratio generated for GAMs due to the non-linear relationship between predictors and the log odds of EHI. As an example, the odds ratio between two arbitrary WBGT points is displayed. The odds of EHI among those exposed to a mean WBGT of 85°F is 2.55 (95% CI: 2.45, 2.64) times the odds of EHI among those exposed to a mean WBGT of 80°F. The association between the log odds of EHI and relative humidity, controlling for month, day of week, installation, and temperature (model 4) is displayed in Figure 2. The odds of EHI among those exposed to 80% relative humidity is 1.36 (95% CI: 1.33, 1.39) times the odds of EHI among those exposed to 60% relative humidity.ConclusionsOur results provide evidence that there is no significant difference in model prediction of EHI utilizing various combinations of weather predictors. However, there is a significant non-linear association between weather predictors and EHI and examples of these relationships are given using different models. Model performance can be improved by including more granular exposure data (i.e. physical activity during EHI episode, biometric and physiological measures).

Male infertility among bakers associated with exposure to high environmental temperature at the workplace.

ObjectiveThis study aimed to evaluate the prevalence of male infertility among bakers exposed to high environmental temperature.MethodsThis cross-sectional study was conducted to obtain information using a validated questionnaire administered through an interview. The mean wet bulb globe temperature (WBGT) index in the bakeries was measured. A new statistical formula was used to estimate the prevalence of infertility among bakers.ResultsA total of 137 bakers working in 20 bakeries and 107 individuals included in the comparable control group with variations in age, race, marital status, and income and with history of cigarette smoking were recruited. Using a newly devised formula, the prevalence of infertility among the exposed group was 22.7%, compared with 3.0% in the control group (p = 0.013). All possible confounding factors associated with infertility among bakers were excluded such as cigarette smoking, age, and race. There were unfavorable hot working conditions in bakeries, with a WBGT index of 37.4 °C, while the average WBGT for offices was 25.5 °C (p < 0.0001).ConclusionOur study showed that the rate of infertility among bakers was high, which resulted from exposure to high environmental temperature at the workplace as evidenced by the WBGT index. This finding should alert the healthcare authorities to take necessary measures under the labor code to curtail infertility among bakers.

Assessment of occupational exposure to heat stress and solar ultraviolet radiation among groundskeepers in an eastern North Carolina university setting

ABSTRACTGroundskeepers spend most of the year working outdoors, exposing them to heat and solar ultraviolet (UV) radiation and increasing their risk to related adverse health effects. Various studies on heat and UV exposures in different occupations have been published, but those on groundskeepers are rare. The purpose of this study was to assess the exposure to heat stress and solar UV radiation among groundskeepers in an eastern North Carolina university setting. Wet bulb globe temperature (WBGT) index using a heat stress monitor and UV effective irradiance (UVeff) index using a digital UV meter were recorded in various work areas three times a day (morning, noon, afternoon) and during three seasons (spring, summer, fall). Data analysis was conducted using descriptive statistics, analysis of variance (ANOVA), Tukey Honestly Significant Difference (HSD), and Pearson Correlation tests. The mean (±SD) WBGT index was the highest in the afternoon (25.4 ± 5.0°C), summer (27.8 ± 3.1°C), and July (29.0 ± 2.6°C); the mean UVeff index was the highest at noon, summer and June (0.0116 ± 0.0061, 0.0101 ± 0.0081, and 0.0114 ± 0.0089 mW/cm2, respectively). Differences in the mean WBGT and UVeff indices within the time periods of day, seasons and months were significant (P < 0.01). The overall correlation between WBGT and UV indices was moderate (r = 0.42, P < 0.01) but lack of correlation was found during different times of the day during the fall and summer seasons. The largest percentages of WBGT indices exceeding the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs) for different workloads were found in the afternoon (11.3–40.7%), summer (14.6–56%), and July (28.8–76.3%). The mean UVeff for noon (0.0116 mW/cm2) and afternoon (0.0100 mW/cm2) exceeded the TLV for 30-min exposure. This study shows that groundskeepers are potentially exposed to excessive heat stress and UV radiation, and are at risk to developing heat- and UV-related illnesses. The study findings will be beneficial in implementing recommended control measures to prevent heat stress and UV exposure among groundskeepers and other similar outdoor workers.

Exertional Heat Illness in American Football Players: When Is the Risk Greatest?

Knowledge about the specific environmental and practice risks to participants in American intercollegiate football during preseason practices is limited. Identifying risks may mitigate occurrences of exertional heat illness (EHI). To evaluate the associations among preseason practice day, session number, and wet bulb globe temperature (WBGT) and the incidence of EHI. Descriptive epidemiology study. Sixty colleges and universities representing 5 geographic regions of the United States. National Collegiate Athletic Association football players. Data related to preseason practice day, session number, and WBGT. We measured WBGT every 15 minutes during the practice sessions and used the mean WBGT from each session in the analysis. We recorded the incidence of EHIs and calculated the athlete-exposures (AEs). A total of 553 EHI cases and 365 810 AEs were reported for an overall EHI rate of 1.52/1000 AEs (95% confidence interval [CI] = 1.42, 1.68). Approximately 74% (n = 407) of the reported EHI cases were exertional heat cramps (incidence rate = 1.14/1000 AEs; 95% CI = 1.03, 1.25), and about 26% (n = 146) were a combination of exertional heat syncope and heat exhaustion (incidence rate = 0.40/1000 AEs; 95% CI = 0.35, 0.48). The highest rate of EHI occurred during the first 14 days of the preseason period, and the greatest risk was during the first 7 days. The risk of EHI increased substantially when the WBGT was 82.0°F (27.8°C) or greater. We found an increased rate of EHI during the first 14 days of practice, especially during the first 7 days. When the WBGT was greater than 82.0°F (27.8°C), the rate of EHI increased. Sports medicine personnel should take all necessary preventive measures to reduce the EHI risk during the first 14 days of practice and when the environmental conditions are greater than 82.0°F (27.8°C) WBGT.

Performance loss among workers due to heat stress in high-temperature workplaces

Background: Heat stress is one of the harmful factors present in many workplaces. It can lead to performance loss and low functionality of the labor force. Therefore, the aim of this study was to evaluate exposure to heat stress and its consequent performance loss among workers functioning in indoor high-temperature workplaces. Materials and Methods: This descriptive, analytical study was conducted on indoor high-temperature occupations in spring 2014. This study was conducted on 15 bakeries, 11 restaurants and kitchens, and 2 industries with heating processes in Gonabad city, Iran. In total, 1450 individuals worked on the investigated sites and were exposed to thermal stress. The inclusion criterion for this study was working in an environment that included a heating process and the exclusion criterion was unwillingness to participate in the study. Heat stress was measured based on wet-bulb globe temperature(WBGT) and the ISO 7243standard. The graph of performance loss versus thermal stress proposed by Kjellstrom et al. was used to determine the performance loss caused by thermal stress.All individuals and managers were informed of the aims of the project and were assured of the confidentiality of the data. Statistical analyses were performed using SPSS software. Results: The mean exposure to heat stress in Barbari, Sangak, and Lavash (three types of bread) bakeries were 29.73, 27.89, and 29.43 °C, with a mean performance loss of 65%, 23%, and 64%, respectively. In some cases, the performance loss in Lavash bakeries was as high as 98%. The mean exposure to heat stress in refractory brick and porcelain manufacturing industries were 32.04 oC and 32.35 °C, leading to a concomitant performance loss of 89% and 92%, respectively. The mean WBGT in the kitchens was 31.88, which could lead to a performance loss of 80%. Conclusions: In addition to a host of diseases and complications caused by heat stress, extreme heat in the workplace can significantly reduce the performance of the labor force, and consequently,their production. Through appropriate planning and control of heat stress in the workplace, not only are many diseases prevented, but also the performance and efficiency of workers are greatly improved.

Assessment of the Impact of Metropolitan-Scale Urban Planning Scenarios on the Moist Thermal Environment under Global Warming: A Study of the Tokyo Metropolitan Area Using Regional Climate Modeling

Using a high-resolution regional climate model coupled with urban canopy model, the present study provides the first attempt in quantifying the impact of metropolitan-scale urban planning scenarios on moist thermal environment under global warming. Tokyo metropolitan area is selected as a test case. Three urban planning scenarios are considered: status quo, dispersed city, and compact city. Their impact on the moist thermal environment is assessed using wet-bulb globe temperature (WBGT). Future projections for the 2070s show a 2–4°C increase in daytime mean WBGT relative to the current climate. The urban scenario impacts are shown to be small, with a −0.4 to +0.4°C range. Relative changes in temperature and humidity as the result of a given urban scenario are shown to be critical in determining the sign of the WBGT changes; however, such changes are not necessarily determined by local changes in urban land surface parameters. These findings indicate that urban land surface changes may improve or worsen the local moist thermal environment and that metropolitan-scale urban planning is inefficient in mitigating heat-related health risks for mature cities like Tokyo.

Skin temperature responses following a warm‐weather road race (1104.4)

Purpose: To quantify the skin temperature changes following intense exercise in warm‐weather. Methods: Anterior thermal images and gastrointestinal temperature (TGI) from 20 male runners (mean±SD; 73.5 ± 10.9 kg) participating in a 11.2 km road race were collected before and immediately after the race. Wet‐bulb globe temperature (WBGT) and wind speed were recorded at the finish line. Infrared thermal images were divided into 11 distinct regions, superior torso (ST), inferior torso (IT), face (F), right forearm (RF), left forearm (LF), right upper arm (RUA), left upper arm (LUA), right thigh (RT), left thigh (LT), right lower leg (RLL) and left lower leg (LLL). Mean weighted anterior skin temperature (MWST) was calculated via approximation of body surface area. Paired samples t‐tests were performed to compare pre‐ and post‐race values. Correlation analysis was performed to evaluate the relationship between MWST and TGI. Results: Mean WBGT was 27.04 ± 1.20 °C. Mean wind speed was 1.38 ± 0.87 km/h. TGI significantly increased from pre‐ to post‐race (pre: 37.18 ± 0.37 °C, post: 39.39 ± 0.73 °C, p&lt;0.001). MWST decreased, approaching significance (pre: 30.46 ± 1.77 °C, post: 29.48 ± 0.95 °C, p=0.059). Mean skin temperature for ST (p=0.001), IT (p&lt;0.001), RUA (p=0.015) and LUA (p=0.004) significantly decreased from pre‐race values. There was no relationship between Post‐TGI and Post‐MWST (r=0.052, p=0.848). Conclusions: Despite a significant increase in TGI, skin temperature decreased compared to pre‐race measures. ST, IT, RUA and LUA may represent the areas with the greatest potential for heat loss, given the air to skin temperature gradient.Grant Funding Source: Supported by The Falmouth Road Race, The American Physiological Society and a UConn SURF Award

Exceedance of heat index thresholds for 15 regions under a warming climate using the wet‐bulb globe temperature

AbstractThermal comfort is quantified in 15 regions using the wet‐bulb globe temperature (WBGT), examining past and future rates of thresholds exceedance corresponding to moderate, high, and extreme heat (28, 32, and 35 °C, respectively). As recent changes to thermal comfort appear to be dominated by temperature and humidity, a WBGT approximation based only on these is used. A new homogenised dataset from 1973 to 2003 is developed which provides WBGT daily means, daily maximums averaged over 5‐day periods, and the highest extreme for each 5‐day period; recent trends are positive for all regions except northeast USA and northeast Australia. A simple model for predicting summertime threshold exceedance rates, with a fixed distribution of anomalies about the seasonal mean, is found to adequately predict changes for the above quantities given seasonal mean values. This model is used to predict the impact of regional 1–5 °C temperature increases on WBGT exceedance rates with no change in relative humidity. Results show that heat events may worsen as much, or more, in humid tropical and mid‐latitude regions even if they warm less than the global average, due to greater absolute humidity increases. A further 2 °C warming from the present is sufficient to push peak WBGT above 35 °C, an extreme heat event, in all regions except the UK.An ensemble of HadCM3 climate model simulations is used to investigate likely regional changes in mean summertime temperature, relative humidity and WBGT under an A1B scenario for the 2020s and 2050s. Unsurprisingly, simulated regional changes often depart significantly from the global average, and the impact of regional changes in relative humidity is not always negligible. Increases in WBGT are nonetheless expected in all regions, and are more predictable than increases in temperature at least in mid‐latitude regions owing to the compensating effects of humidity. © 2010 Royal Meteorological Society and Crown Copyright

Rapid Cooling Of An NFL Defensive Linemen With A Core Temperature Of 40.9 2C During A Full Padded Practice

HISTORY The athlete is a 9 yr veteran defensive lineman in the National Football League (NFL) with age = 30 yr, height =182.9 cm and body fat = 24%. He arrived at pre-season training camp 2004 with mass = 149 kg, similar to his 2003 pre-season mass (147.7 kg). He gained 5.6 kg by the 5th morning, 3.76% above baseline (BL). His sweat rate was 1.7 l·hr-1 in 2003 with ambient temperature = 23.7 °C and 83% RH. In pre-season 2003 his mean percent dehydration (%Dehy) after practice was 0.87% ranging from 0.0 to 1.85% in 23 consecutive practices. During the first 3 days of the 2004 pre-season this player's core temperature (Te) was monitored using ingestible sensors (HQ, Inc.). On Day 1 of two-a-days, his Te was >39.5°C (103°F) at the end of a one h indoor morning (AM) practice. Wet bulb globe temperature (WBGT) was 24.4°C and he was dressed in a helmet, shorts and shell. He denied a history of heat associated illness. PHYSICAL EXAMINATION The subjects' Te was closely monitored during the afternoon (PM) full padded practice due to his elevated AM Te. While dressed in shorts and a Tee-shirt, his resting Te recorded in an air-conditioned area 45 min prior to PM practice was 37.8°C (100°F). His Te was monitored approximately every 8 min during PM practice and he was questioned frequently about heat-related symptoms. His Te steadily increased to 40°C (104°F) by 1 h and 30 min into practice and he denied symptoms other than he felt hot. When his Te increased to 40.6°C (105°F) he was removed from practice against his will. His equipment was removed and he was transported to the on-field medical tent. Mean WBGT assessed three times during practice was 28.3°C. DIFFERENTIAL DIAGNOSIS Malignant hyperthermia Exercise induced heat stroke Exercise associated hyperthermia (benign) TEST AND RESULTS Te monitoring (40.9°C which decreased with cooling) Cognitive testing (−) Visual assessment (+ mild visual disturbance) % Dehydration (0% from baseline) FINAL WORKING DIAGNOSIS Benign exercise associated hyperthermia. TREATMENT AND OUTCOMES The athlete was removed from practice and rapidly cooled with ice-water soaked vests, neck collars and caps. His Te increased from 40.6°C when removed from practice to 40.9°C (105.7°F) just prior to aggressive cooling. While Te was continuously monitored the ice-water vests, collars and caps were changed approximately every 45 – 90 sec. A total of 6 changes were used for this player. Tc decreased from 40.9°C to 38.7°C (101.7°F) within 10 min of cooling. He had no residual symptoms or subsequent heat-associated problems. His post-practice % Dehy was 1.36% from pre-practice but 0% from BL. The highest Te recorded in this athlete on the 10th day of pre-season was 39.4°C (103°F).

Thermal Responses and Body Fluid Balance of Competitive Male Swimmers During a Training Session

Thermoregulatory and body fluid balance (BFB) responses of competitive swimmers were studied during a typical interval training session under natural field conditions. Sub-jects were 9 males (18.0 ± 1.7 years; VO2max 5 3.8 ± 0.9 L·min 21) who covered 9,000 m in 180 minutes in an outdoor pool (mean water temperature 5 26.8 ± 0.38 C; mean wet bulb globe temperature 5 29.8 ± 2.88 C). Mean body weight (BWt) decreased by 1.8 ± 0.5 kg (P < 0.05), and rectal tem-perature increased by 1.0 ± 1.08 C (P < 0.05). Volitional water intake (WI) (0.1 ± 0.2 kg) did not maintain BFB (20.5 kg per hour) and plasma volume decreased 10.7 ± 5.4%. During a typical training session, swimmers experienced significant body fluid losses, and WI was not enough to prevent involuntary dehydration. The magnitude of the fluid losses (2.5% of BWt) was sufficient to compromise convective thermoregulation because of the decreased plasma volume. Hence, to prevent involuntary dehydration, swimmers should be encouraged to consume an amount of fluids that equals losses throughout the training sessions.

Thermal responses and body fluid balance of competitive male swimmers during a training session.

Thermoregulatory and body fluid balance (BFB) responses of competitive swimmers were studied during a typical interval training session under natural field conditions. Subjects were 9 males (18.0 +/- 1.7 years; VO(2)max = 3.8 +/- 0.9 L x min(-1)) who covered 9,000 m in 180 minutes in an outdoor pool (mean water temperature = 26.8 +/- 0.3 degrees C; mean wet bulb globe temperature = 29.8 +/- 2.8 degrees C). Mean body weight (BWt) decreased by 1.8 +/- 0.5 kg (P < 0.05), and rectal temperature increased by 1.0 +/- 1.0 degrees C (P < 0.05). Volitional water intake (WI) (0.1 +/- 0.2 kg) did not maintain BFB (-0.5 kg per hour) and plasma volume decreased 10.7 +/- 5.4%. During a typical training session, swimmers experienced significant body fluid losses, and WI was not enough to prevent involuntary dehydration. The magnitude of the fluid losses (2.5% of BWt) was sufficient to compromise convective thermoregulation because of the decreased plasma volume. Hence, to prevent involuntary dehydration, swimmers should be encouraged to consume an amount of fluids that equals losses throughout the training sessions.

The risk of heat exhaustion at a deep underground metalliferous mine in relation to surface temperatures.

The risk of heat exhaustion at a deep underground metalliferous mine was assessed in relation to thermal conditions prevailing on the surface. For each day of a 1-year prospective case series of heat exhaustion, surface 24-h mean wet and dry bulb temperatures were recorded. From this data, 24-h mean wet bulb globe temperatures were derived using certain assumptions. The three surface temperature variables were significantly higher on those days on which heat exhaustion occurred, compared to those days on which it did not occur (P < 0.001). The relative risk of heat exhaustion on days when the 24-h mean wet bulb globe temperature was in the range 26.0-28.0 degrees C was 4.82 (95% confidence interval 2.12-10.96). Surface temperature data could be used at this mine to warn miners about the risk of heat exhaustion.