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Regional heat safety thresholds for athletics in the contiguous United States

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... Meteorological services use indicators such as the NOAA heat index (Rothfusz, 1990;Steadman, 1979), Humidex (Masterson & Richardson, 1979; as cited in Blazejczyk et al., 2012) or Perceived Temperature (Staiger et al., 2011) to provide heat warnings. Wetbulb globe temperature is often used to assess occupational illness and injuries caused by heat stress (e.g., Garzon-Villalba et al., 2016), to estimate heat-related decreases of worker productivity (e.g., Orlov et al., 2019), to derive heat safety recommendations for athletes (Grundstein et al., 2015;Racinais et al., 2015), and for military purposes (Budd, 2008). Several HSIs were originally developed to measure the thermal comfort of humans. ...
... To classify the severity of human heat stress, we thus employ impact-relevant thresholds. While epidemiological studies usually do not consider absolute thresholds, safety regulations for occupational athletic health as well as meteorological heat warnings do rely on specific thresholds (Blazejczyk et al., 2012;Grundstein et al., 2015;Parsons, 2006;Racinais et al., 2015, see also Table S2). Due to the different purposes for which thresholds were developed, no uniform impact assessment scheme exists for HSIs and the thresholds applied in the present study are gathered from various sources. ...
... Additionally, human sensitivity to heat can depend on various other factors such as workload, age, or socioeconomic status (McMichael et al., 2006;. Consequently, different threshold levels have been defined to integrate these factors at least partially (e.g., Grundstein et al., 2015;. When applying different thresholds to one indicator, the exceedance rates can change considerably, as shown in Figure S15 for nine different T WBG thresholds. ...
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Abstract Global warming is leading to increased heat stress in many regions around the world. An extensive number of heat stress indicators (HSIs) has been developed to measure the associated impacts on human health. Here we calculate eight HSIs for global climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). We compare their future trends as function of global mean temperature, with particular focus on highly populated regions. All analyzed HSIs increase significantly (p
... The "National Athletic Trainers' Association Position Statement: Exertional Heat Illness" (NATA-PS) sets forth guidelines supporting the assertion that the occurrence of EHS can be reduced and death can be prevented when proper strategies are in place [2]. Mainly, monitoring environment conditions can reduce the likelihood of EHS occurring (e.g., prevention) [2][3][4][5][6][7][8][9] whilst proper treatment using cold water immersion (CWI) initiated rapidly following an EHS diagnosis appears to eliminate the chance of death (e.g., treatment) [2,8,10,11]. While a number of modifiable and unmodifiable risk factors contribute to the onset of EHS, careful consideration, development, and implementation of various mitigation strategies has been evidenced to be successful in attenuating EHS risk [6,7,12]. ...
... Environmental factors (e.g., extreme heat and/or humidity) increase the risk of EHS as the external heat load impedes dissipation of body heat, especially during exercise. Environmental heat has long been considered a risk factor for EHS and is consistently cited within scientific and medical literature as a factor to address when developing heat mitigation strategies [2][3][4][5]7,8,10,13,14]. Recent evidence shows that EHS is more likely to occur when environmental conditions exceed normative data based on geographical location, thus prompting the need for region-specific activity modifications [3,4]. ...
... Environmental factors (e.g., extreme heat and/or humidity) increase the risk of EHS as the external heat load impedes dissipation of body heat, especially during exercise. Environmental heat has long been considered a risk factor for EHS and is consistently cited within scientific and medical literature as a factor to address when developing heat mitigation strategies [2][3][4][5]7,8,10,13,14]. Recent evidence shows that EHS is more likely to occur when environmental conditions exceed normative data based on geographical location, thus prompting the need for region-specific activity modifications [3,4]. Current best practice recommendations advocate for the use of wet bulb globe temperature (WBGT) as the meteorological index that is most appropriate for quantifying environmental heat stress [2,8,13]. ...
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Background and objectives: Exertional heat stroke (EHS) continues to be a prevalent health issue affecting all athletes, including our pediatric populations. The purpose of this study was to evaluate the effect of a state policy requirement for EHS prevention and treatment on local high school policy adoption in the United States (US). Materials and Methods: Athletic trainers (ATs) from high schools across the US participated in an online survey (n = 365). This survey inquired about their compliance with nine components of an EHS policy which was then compared to their state requirements for the policies. Evaluation of the number of components adopted between states with a requirement versus states without a requirement was conducted with a Wilcoxon Sign Rank test. Finally, an ordinal logistic regression with proportional odds ratios (OR) with 95% confidence intervals (CI) were run to determine the effect of a state requirement and regional differences on the number of components adopted. Results: ATs working in states with a requirement reported adoption of more components in their heat modification policy compared to states that did not require schools to develop a heat modification policy (with requirement mean = 5.34 ± 3.68, median = 7.0; without requirement mean = 4.23 ± 3.59, median = 5.0; Z = −14.88, p < 0.001). ATs working in region 3 (e.g., hotter regions) reported adopting more components than those in region 1 (e.g., cooler regions) (OR = 2.25, 95% CI: 1.215-4.201, p = 0.010). Conclusions: Our results demonstrate a positive association between state policy requirements and subsequently increased local policy adoption for EHS policies. Additionally, the results demonstrate that regional differences exist, calling for the need for reducing disparities across the US. These findings may imply that policy adoption is a multifactorial process; furthermore, additional regional specific investigations must be conducted to determine the true determinants of high school policy adoption rates for EHS policies.
... Tnwb reflects the evaporation rates and it is regulated by relative humidity, radiation levels and wind. The calculation of outdoor WBGT aligns very well with the measured data (Grundstein et al., 2015). ...
... It is worth mentioning that endeavouring to encompass different human tolerance to heat is not simple, since acclimatisation of individuals depends on physiological adaptations that occur after constant exposure to hot environments (Armstrong and Maresh, 1991). Constant exposure to heat makes an individual more resistant to heat stress, developing a greater sweat rate along with increased heart function, fluid balance and skin circulation (Grundstein et al., 2015). The magnitude of these physiological changes lies with the duration, intensity and frequency of human heat exposure. ...
... In general, resistance to heat exposure varies geographically. Even though heat illness may occur more often in hotter climates, due to higher levels of heat exposure, it is noted that people in cooler regions may be more vulnerable to hot spells because they are not acclimatised to extreme conditions (Grundstein et al., 2015). Thus, it is important to highlight that to provide guidance, the specified WBGT limits above in Table 1 were adopted in the evaluation of heat stress in outdoor environments from both the Guaratiba and São Cristovão locations. ...
Article
This paper aims to assess the effects of urbanization on heat stress comparing two neighbourhoods in the tropical city of Rio de Janeiro, Brazil, that differ in terms of building density and vegetation cover. The outdoor heat stress was evaluated by the Wet Bulb-Globe Temperature (WBGT) Index, which considers the combined effect of air temperature, relative humidity, solar radiation and wind speed, during the year of 2016. The urban neighbourhood presented statistically (p < 0.01) higher WBGT levels (mean value 23.48°C), than the suburban neighbourhood (mean value 22.0°C). The results highlighted the effect of low wind velocities on heat stress in the urban environment over 75% of the time. Building spacing and street orientation considering the most frequent wind directions must be taken into account during the urban planning process. Otherwise stagnant air conditions in urban environments become a common feature that cannot be reverted. Under such circumstances, green areas such as pocket parks, green roofs and green walls should be implemented to mitigate heat stress. Public policies for many neighbourhoods in Brazilian cities are necessary to increase vegetated areas aiming to improve conditions of well-being.
... Consistent with the base -first definition, the second one replaces the AirT with WBGT to include the influence of air humidity. The WBGT was initially used for determining the heat stress among industrial hygienists, athletes, sporting events and the military (Armstrong et al., 2007;Grundstein et al., 2015), with the integration of solar exposure, air temperature, humidity and wind speed (Yaglou and Minaed, 1957;Lemke and Kjellstrom, 2012). ...
... The corresponding positive gaps in terms of WBGT were 5.1 • C, 6.1 • C, 4.9 • C and 5.1 • C and in terms of AppT were 7.0 • C, 7.6 • C, 7.0 • C and 7.4 • C. This indicates the significantly elevated temperature, enhanced heat stress and worsened human thermal comfort under HW conditions, under such conditions the outdoor activity patterns should be significantly weakened or ceased for health and safety considerations (ACSM, 1984;Grundstein et al., 2015). ...
... Astonishingly, if we take WBGT as temperature indicator, the maximum temperature exceeded the threshold of the most critical heat stress (no outdoor workouts) even under NHW conditions. Meanwhile, the minimum temperature was still high, exceeding the threshold of limited intense exercise and that of plan intense exercise (Grundstein et al., 2015;ACSM, 1984). Therefore, the urban heat emergency response plan is also required under normal conditions. ...
Article
Heat waves (HWs) and urban heat islands (UHIs) can potentially interact. The mechanisms behind their synergy are not fully disclosed. Starting from the localized UHI phenomenon, this study aims i) to reveal their associated impacts on human thermal comfort through three different definitions of HW events, based on air temperature (airT), wet-bulb globe temperature (WBGT) and human-perceived temperature (AppT) respectively, and ii) to understand the role of air moisture and wind. The analysis was conducted in four districts (NH, JD, MH and XJH) with different urban development patterns and geographic conditions, in the megacity of Shanghai with a subtropical humid climate. Results evidenced the localized interplay between HWs and UHIs. The results indicate that less urbanized districts were generally more sensitive to the synergies. JD district recorded the highest urban heat island intensity (UHII) amplification, regardless of the specific HW definition. Notably, during AppT-HWs, the increment was observed in terms of maximum (1.3 °C), daily average (0.8 °C), diurnal (0.4 °C) and nocturnal UHII (1.0 °C). Nevertheless, localized synergies between HWs and UHIs at different stations also exhibited some commonalities. Under airT-HW, the UHII was amplified throughout the day at all stations. Under WBGT-HW, diurnal UHII (especially at 11:00–17:00 LST) was consistently amplified at all stations. Under AppT-HW conditions, the nocturnal UHII was slightly amplified at all stations. Air moisture and wind alleviated the synergistic heat exacerbation to the benefit of thermal comfort. The extent depended on geographic condition, diurnal and nocturnal scenarios, temperature type and HW/normal conditions. Stronger HW-UHI synergies indicate the necessity to develop specific urban heat emergency response plans, able to capture and intervene on the underlying mechanisms. This study paves to way to their identification.
... This approach has also been applied in a previous COMFA-related study . The WBGT heat stress scale, which targets hot regions, was adopted in this study (Grundstein, Williams, Phan, & Cooper, 2015). The activity guidelines were based on the Practice Policy for Heat and Humidity from the Georgia High School Association (2020). ...
... The activity guidelines were based on the Practice Policy for Heat and Humidity from the Georgia High School Association (2020). Its recommendations were based on the corresponding WBGT heat stress categories (Grundstein et al., 2015). ...
... Heat disorders (Harlan, Brazel, Prashad, Stefanov, & Larsen, 2006) HI (Harlan et al., 2006) WBGT (Grundstein, Williams, Phan, & Cooper, 2015) COMFA for children, young athletes, adults (Harlan et al., 2006) Activity guidelines (GHSA, 2020) Z. Liu and C.Y. Jim the longest duration in "Danger" on sunny days, followed by cloudy days and the overcast day. The turf materials slightly affected the heat stress duration. ...
Article
Exercising in an unusually hot environment may aggravate exertional heat illness. Turf material significantly affects the microenvironment and heat-stress sensation of sports-field users. However, the difference in human- biometeorological effects between different sports-field turf materials demands further investigation. This study compared artificial (AT) with natural turf (NT) fields, investigating three age groups (children, young athletes, and adults), two physical activities (playing soccer and walking), and three heat stress indicators (HI, Heat Index; WBGT, Wet Bulb Globe Thermometer; and COMFA, COMfort FormulA). The results showed heat-stress underestimation by HI and WBGT. In contrast, COMFA, incorporating comprehensive environmental and human physiological parameters, provided a more targeted and reliable heat-stress assessment. COMFA indicated a longer heat-stress duration exercising at AT than NT. Compared to NT, children suffered a 24% longer “Extreme danger” duration at AT in sunny daytime. The AT-NT difference in human-biometeorological effect was limited concerning human convection, evaporation, metabolic heat, and emitted longwave radiation, but was considerable in human absorbed radiation. AT had lower albedo than NT, hence field users absorbed more upward longwave radiation but less upward shortwave radiation, highlighting important control by the radiant environment. NT sports fields are recommended for a healthy outdoor thermal environment, especially for children.
... 49 Overall physical activity in children decreased by about 18%, and physical inactivity (sedentary behavior) increased by 5.5% during summer vacations. 50 Decreases in physical activity participation trends can be exacerbated as summers continue to warm, including more extensive heat waves 51 and changing patterns of high daytime and nighttime temperature and other extreme heat events. ...
... Heat risk was projected to be highest in areas from Texas to South Dakota, with 25 to 60 days exceeding the safety cutoff, and more than 85 days could exceed cutoffs in states along the Gulf Coast. 51 These data were used to further refine ACSM categories of risk, incorporating these regional temperature variations affecting risk level for more region-specific risk categories. 51 A study in New York City found an association between temperature indicators and total hours and daily average distance of outdoor cycling. ...
... 51 These data were used to further refine ACSM categories of risk, incorporating these regional temperature variations affecting risk level for more region-specific risk categories. 51 A study in New York City found an association between temperature indicators and total hours and daily average distance of outdoor cycling. A linear increase in total hours and daily average distance, up to a maximum air temperature threshold of 78.8 F (26 C) to 82.4 F (28 C) was found, with a drastic decrease in daily time or distance at this temperature threshold (humidity was not measured). ...
Article
Climate change has led to increased frequency, intensity, and duration of extreme heat events with dire consequences for health. These are the deadliest of climate change impacts with preventable mortality from heat-related illnesses and increased threat to safe participation in physical activity and sports. Nurse practitioners can collaborate with community and professional sports health organizations to ensure evidence-based health and safety policies to reduce health-related risks. Adverse consequences on engagement in key health-promoting physical activity and sports may catalyze urgent action to address climate change.
... Such measurements should also be taken on-site relative to the specific event, as local measurements of WBGT can vary significantly [11,12]. Additionally, climatological-region-referenced recommended ranges (i.e., northern US, middle US, southern US, as delineated by Grundstein et al. [13]) for these WBGT values have been proposed to reflect differences in typical environmental conditions experienced across the US [13]. These policy recommendations are reiterated through statements by the American College of Sports Medicine [14] and reflect similar guidelines in the US military and occupational safety communities [5]. ...
... Such measurements should also be taken on-site relative to the specific event, as local measurements of WBGT can vary significantly [11,12]. Additionally, climatological-region-referenced recommended ranges (i.e., northern US, middle US, southern US, as delineated by Grundstein et al. [13]) for these WBGT values have been proposed to reflect differences in typical environmental conditions experienced across the US [13]. These policy recommendations are reiterated through statements by the American College of Sports Medicine [14] and reflect similar guidelines in the US military and occupational safety communities [5]. ...
... Though Cooper et al. have shown that WBGT >28 • C is associated with greater incidence of exertional heat illness among collegiate football players across the contiguous US [28], retrospective analysis of EHS related fatalities in football players in another study [29] demonstrated that the risk was heightened when the observed WBGT was unexpectedly high based on the local climate. As such, Grundstein et al. proposed a regional heat safety threshold that accounts for variations in climate pattern observed across the contiguous US [13]. The proposed regional adjustments resulted in raising the activity modification threshold for regions that are traditionally hot, ensuring that athletes could still participate in physical activities with proper risk mitigation measures, while detecting unusually warm days in traditionally cool regions by lowering their activity modification thresholds [13]. ...
Article
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Background and objectives: Environmental monitoring allows for an analysis of the ambient conditions affecting a physically active person's ability to thermoregulate and can be used to assess exertional heat illness risk. Using public health models such as the precaution adoption process model (PAPM) can help identify individual's readiness to act to adopt environmental monitoring policies for the safety of high school athletes. The purpose of this study was to investigate the adoption of policies and procedures used for monitoring and modifying activity in the heat in United States (US) high schools. Materials and Methods: Using a cross-sectional design, we distributed an online questionnaire to athletic trainers (ATs) working in high schools in the US. The questionnaire was developed based on best practice standards related to environmental monitoring and modification of activity in the heat as outlined in the 2015 National Athletic Trainers' Association Position Statement: Exertional Heat Illness. The PAPM was used to frame questions as it allows for the identification of ATs' readiness to act. PAPM includes eight stages: unaware of the need for the policy, unaware if the school has this policy, unengaged, undecided, decided not to act, decided to act, acting, and maintaining. Invitations were sent via email and social media and resulted in 529 complete responses. Data were aggregated and presented as proportions. Results: Overall, 161 (161/529, 30.4%) ATs report they do not have a written policy and procedure for the prevention and management of exertional heat stroke. The policy component with the highest adoption was modifying the use of protective equipment (acting = 8.2%, maintaining = 77.5%). In addition, 28% of ATs report adoption of all seven components for a comprehensive environmental monitoring policy. Conclusions: These findings indicate a lack of adoption of environmental monitoring policies in US high schools. Secondarily, the PAPM, facilitators and barriers data highlight areas to focus future efforts to enhance adoption.
... The creation of EHS preparedness guidelines based on geographic location allows for appropriate modifications to be implemented for the population at risk. 8 For example, exercise modifications in generally cooler regions should not be the same as those in hotter regions because of different levels of passive heat acclimatization. During heat waves, high schools in relatively cooler areas may have athletes who are not acclimatized to this extreme, and the schools' policies may not offer sufficient protection. ...
... Regions were grouped on the basis of extreme (90th-percentile) daily maximum WBGT. 8 State-Level Mandates for Preseason Heat Acclimatization (Main Exposure). Earlier authors 9 found that high school football programs located in states whose athletic associations mandated guidelines for preseason football heat acclimatization were more likely to use EHSprevention strategies. ...
... In fact, the heat-safety regions were developed to account for regional differences in athletes' acclimatization to the environment, understanding that individuals in hotter regions are likely partially and passively heat acclimatized and can withstand slightly higher temperatures. 8 Previous researchers 5 estimated that 25% of fatal EHS events occurred in regions 1 and 2; of these, 80% occurred in above-average WBGTs. The absolute WBGTs for those cases would not have necessarily been considered above average in region 3, 5 emphasizing the need for a regional approach to prevention and management preparedness. ...
Article
Context: Exertional heat stroke (EHS) is a leading cause of sudden death in high school football players. Preparedness strategies can mitigate EHS incidence and severity. Objective: To examine EHS preparedness among high school football programs and its association with regional and state preseason heat-acclimatization mandates. Design: Cross-sectional study. Setting: Preseason high school football programs, 2017. Patients or other participants: A total of 910 athletic trainers (ATs) working with high school football (12.7% completion rate). Main outcome measure(s): We acquired data on high school football programs' EHS preparedness strategies in the 2017 preseason via an online questionnaire, looking at (1) whether schools' state high school athletic associations mandated preseason heat-acclimatization guidelines and (2) heat safety region based on warm-season wet-bulb globe temperature, ranging from the milder region 1 to the hotter region 3. Six EHS-preparedness strategies were assessed: EHS recognition and treatment education; policy for initiating emergency medical services response; emergency response plan enactment; immersion tub filled with ice water before practice; wet-bulb globe temperature monitoring; and hydration access. Multivariable binomial regression models estimated the prevalence of reporting all 6 strategies. Results: Overall, 27.5% of ATs described their schools as using all 6 EHS-preparedness strategies. The highest prevalence was in region 3 schools with state mandates (52.9%). The combination of a higher heat safety region and the presence of a state mandate was associated with a higher prevalence of reporting all 6 strategies (P = .05). Controlling for AT and high school characteristics, the use of all 6 strategies was higher in region 3 schools with state mandates compared with region 1 schools without state mandates (52.9% versus 17.8%; prevalence ratio = 2.68; 95% confidence interval = 1.81, 3.95). Conclusions: Our findings suggest a greater use of EHS-preparedness strategies in environmentally warmer regions with state-level mandates for preseason heat acclimatization. Future researchers should identify factors influencing EHS preparedness, particularly in regions 1 and 2 and in states without mandates.
... Table 4. For comparison, we used regional guidelines 23 to indicate the recommended activity based on WBGT measures. Both bands were in category 3. 23 Environmental measures were not different between institutions. ...
... For comparison, we used regional guidelines 23 to indicate the recommended activity based on WBGT measures. Both bands were in category 3. 23 Environmental measures were not different between institutions. Mean WBGT for rehearsals was 28.88C 6 5.28C, for morning game-day rehearsals was 25.68C 6 10.18C, and for games was 32.78C 6 9.98C. ...
Article
Context To our knowledge, no researchers have investigated thermoregulatory responses and exertional heat illness (EHI) risk factors in marching band (MB) artists performing physical activity in high environmental temperatures. Objective To examine core temperature (Tc) and EHI risk factors in MB artists. Design Descriptive epidemiology study. Setting Three rehearsals and 2 football games for 2 National Collegiate Athletic Association Division I institution's MBs. Patients or Other Participants Nineteen volunteers (females = 13, males = 6; age = 20.5 ± 0.9 years, height = 165.1 ± 7.1 cm, mass = 75.0 ± 19.1 kg) completed the study. Main Outcome Measure(s) We measured Tc, wet bulb globe temperature, and relative humidity preactivity, during activity, and postactivity. Other variables were activity time and intensity, body surface area, hydration characteristics (fluid volume, sweat rate, urine specific gravity, percentage of body mass loss), and medical history (eg, previous EHI, medications). The statistical analysis consisted of descriptive information (mean ± standard deviation), comparative analyses that determined differences within days, and correlations that identified variables significantly associated with Tc. Results The mean time for rehearsals was 102.8 ± 19.8 minutes and for games was 260.5 ± 47.7 minutes. Mean maximum Tc was 39.1 ± 1.1°C for games and 38.4 ± 0.7°C for rehearsals; the highest Tc (41.2°C) occurred during a game. Fluid consumption did not match sweat rates (P < .001). Participants reported to games in a hypohydrated state 63.6% of the time. The maximum Tc correlated with the maximum wet bulb globe temperature (r = 0.618, P < .001) and was higher in individuals using mental health medications (rpb = −0.254, P = .022) and females (rpb = 0.330, P = .002). Body surface area (r = −0.449, P < .001) and instrument mass (r = −0.479, P < .001) were negatively correlated with Tc. Conclusions Marching band artists experienced high Tc during activity and should have access to athletic trainers who can implement EHI-prevention and -management strategies.
... The implementation of this idea with athletes, however, is not as simple to effectively implement. For example, regional differences in environmental conditions, such as the mild summers experienced by many across the globe, make it difficult for athletes who are traveling to hotter venues to gain the full benefits of HAz needed prior to competition [2]. ...
... All trials were performed on a motorized treadmill (T150; COSMED, Traunstein, Germany). These environmental conditions were chosen to reflect red flag conditions for physical activity [2]. The number of days between baseline and post-HAz were recorded (baseline and post-HAz, 109 ± 9 days). ...
Article
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The purpose of this study was to assess the effectiveness of heat acclimatization (HAz) followed by heat acclimation (HA) on physiological adaptations. 25 male endurance athletes (age 36 ± 12 y, height 178.8 ± 6.39 cm, body mass 73.03 ± 8.97 kg, and VO2peak 57.5 ± 7.0 mL·kg−1·min−1) completed HAz and HA. HAz was 3 months of self-directed summer training. In the laboratory, a 5-day HA prescribed exercise to target a hyperthermic zone (HZHA) of Trec between 38.50 and 39.75 °C for 60 min. Exercise trials were 60 min of running (59% ± 2% VO2peak) in an environmental chamber (wet bulb globe temperature 29.53 ± 0.63 °C) and administered at: baseline, post-HAz, and post-HAz+HA. Measured variables included internal body temperature (Trec), heart rate (HR), and sweat rate (SR). Repeated measure ANOVAs and post hoc comparisons were used to assess statistically significant (p < 0.05) differences. Trec was lower post-HAz+HA (38.03 ± 0.39 °C) than post-HAz (38.25 ± 0.42 °C, p = 0.009) and baseline (38.29 ± 0.37 °C, p = 0.005). There were no differences between baseline and post-HAz (p = 0.479) in Trec. HR was lower post-HAz (143 ± 12 bpm, p = 0.002) and post-HAz+HA (134 ± 11 bpm, p < 0.001) than baseline (138 ± 14 bpm). HR was lower post-HAz+HA than post-HAz (p = 0.013). SR was higher post-HAz+HA (1.93 ± 0.47 L·h−1) than post-HAz (1.76 ± 0.43 L·h−1, p = 0.027). Combination HAz and HA increased physiological outcomes above HAz. This method can be used to improve performance and safety in addition to HAz alone.
... This may be due in part to the fact that the south has an overall hotter climate and thus may facilitate a higher perceived susceptibility for EHS cases. For example, the 90th percentile warm season (May-September) maximum daily wet-bulb globe temperatures (WBGT) for the northernmost states is~28-30 • C, whereas for the southernmost states the WBGT is~34-36 • C [23]. Our findings also suggest respondents in the south are almost two times more likely to work with ATs when compared to the rest of the country. ...
... In other words, a hot day in Georgia and a hot day in Maine may be vastly different. However, the abnormally hot day in Maine may contribute to an EHS injury just as much as the hot day in Georgia [23]. In contrast, the Northeast was over twice as likely to use best practices for EHS (i.e., rectal temp, CWI, cool-first transport-second) when compared to the rest of the country, even though they were least likely to have an EHS protocol implemented. ...
Article
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Background and Objectives: Emergency Medical Service (EMS) protocols vary widely and may not implement best practices for exertional heat stroke (EHS). EHS is 100% survivable if best practices are implemented within 30 min. The purpose of this study is to compare EMS protocols to best practices for recognizing and treating EHS. Materials and Methods: Individuals (n = 1350) serving as EMS Medical or Physician Director were invited to complete a survey. The questions related to the EHS protocols for their EMS service. 145 individuals completed the survey (response rate = 10.74%). Chi-Squared Tests of Associations (χ2) with 95% confidence intervals (CI) were calculated. Prevalence ratios (PR) with 95% CI were calculated to determine the prevalence of implementing best practices based on location, working with an athletic trainer, number of EHS cases, and years of directing. All PRs whose 95% CIs excluded 1.00 were considered statistically significant; Chi-Squared values with p values < 0.05 were considered statistically significant. Results: A majority of the respondents reported not using rectal thermometry for the diagnosis of EHS (n = 102, 77.93%) and not using cold water immersion for the treatment of EHS (n = 102, 70.34%). If working with an athletic trainer, EMS is more likely to implement best-practice treatment (i.e., cold-water immersion and cool-first transport-second) (69.6% vs. 36.9%, χ2 = 8.480, p < 0.004, PR = 3.15, 95% CI = 1.38, 7.18). Conclusions: These findings demonstrate a lack of implementation of best-practice standards for EHS by EMS. Working with an athletic trainer appears to increase the likelihood of following best practices. Efforts should be made to improve EMS providers' implementation of best-practice standards for the diagnosis and management of EHS to optimize patient outcomes.
... Acclimatization and heat tolerance are regional, and different geographical areas require different environmental algorithms for modifying and canceling activity (105). The recommendations for curtailing activity may change through a season as athletes become fit and acclimatized to the conditions. ...
... Modifying, postponing, or canceling an event can be based on data specific to event outcomes (106,107). A region-specific exercise modification table (Table 7) is an essential primary risk reduction strategy that works for all sports and laborers (105,108,109). Heat safety tables used by institutions should include modifications in activity duration and intensity, increased rest breaks, and removal of extra clothing or equipment. ...
Article
Exertional heat stroke (EHS) is a true medical emergency with potential for organ injury and death. This consensus statement emphasizes that optimal exertional heat illness management is promoted by a synchronized chain of survival that promotes rapid recognition and management, as well as communication between care teams. Health care providers should be confident in the definitions, etiologies, and nuances of exertional heat exhaustion, exertional heat injury, and EHS. Identifying the athlete with suspected EHS early in the course, stopping activity (body heat generation), and providing rapid total body cooling are essential for survival, and like any critical life-threatening situation (cardiac arrest, brain stroke, sepsis), time is tissue. Recovery from EHS is variable, and outcomes are likely related to the duration of severe hyperthermia. Most exertional heat illnesses can be prevented with the recognition and modification of well-described risk factors ideally addressed through leadership, policy, and on-site health care.
... We examined ATs' demographics and HS characteristics using frequencies and percentages. High school characteristics also included the US census region and heat-safety region, 18 both of which were determined on the basis of the HS zip codes provided by the ATs. The heat-safety regions were based on warm-season wet-bulb globe temperatures (WBGTs) from 1991 through 2005, accounted for multiple environmental variables across and within states (including temperature, humidity, wind, and radiant heating), and were grouped by extreme (90th-percentile) daily maximum WBGT. ...
... 32.38C) contained much of the southeastern quadrant of the US, along with portions of the Southwest and the Central Valley of California. 18 Descriptive characteristics were analyzed for the pooled sample of ATs and then separately for ATs who had and those who had not managed a patient with suspected EHS during the 2017 preseason. ...
Article
Context: Athletic trainers (ATs) are educated and trained in appropriate exertional heat-stroke (EHS) management strategies, yet disparities may exist between intended and actual uses in clinical practice. Objective: To examine the intended and actual uses of EHS management strategies among those who did and those who did not treat patients with suspected cases of EHS during the 2017 high school (HS) American football preseason. Design: Cross-sectional study. Setting: Online questionnaire. Patients or other participants: A total of 1016 ATs who oversaw patient care during the 2017 HS American football preseason. Main outcome measure(s): Responding HS ATs recorded whether they had or had not managed patients with suspected EHS events during the 2017 HS American football preseason. Those who had managed patients with suspected cases of EHS reported the management strategies used; those who had not managed such patients described their intended management strategies. For each management strategy, z tests compared the proportions of actual use among ATs who managed patients with suspected EHS with proportions of intended use among ATs who did not manage such patients. Results: Overall, 124 (12.2%) ATs treated patients with suspected EHS cases during the 2017 HS American football preseason. Generally, the proportions of intended use of management strategies among ATs who did not treat patients with suspected EHS were higher than the actual use of those strategies among ATs who did. For example, ATs who did not treat patients with suspected EHS were more likely than those who did not treat such patients to intend to take rectal temperature (19.6% versus 3.2%, P < .001) and immerse the athlete in ice water (90.1% versus 51.6%, P < .001). Conclusions: Inconsistencies occurred between intended and actual use of EHS management strategies. The standard of care for managing patients with suspected cases of EHS were not consistently used in clinical practice, although ATs who did not treat EHS stated they intended to use these management strategies more frequently. Future researchers should identify factors that preclude ATs from using the standard of care when treating patients with suspected cases of EHS.
... This high school is located in the southeast United States, which is Region 3 according to Grundstein's heat safety regions. 19 An AT was present for this race and had set up a medical area with a treatment table, heat stress tracker (Kestrel Model 5400, Boothwyn, PA), cold tub, and coolers with ice and water. At 4:00PM (the start of the race), the wetblub globe temperature (WBGT) was recorded as 86.5° ...
... Being that this occurred in early October rather than during the preseason summer months demonstrates the importance of being prepared regardless of the season or sport. In Category 3 of the heat safety regions 19 to understand that a sudden increase in WBGT can increase the risk of EHS if the environmental conditions has been mild leading up to this day. The main intrinsic factor noted in this case was that the patient had been experiencing an upper respiratory infection in the few days prior to this incident. ...
Article
A 14-year-old female high school cross country runner (height = 154 cm, mass = 48.1 kg) with no history of exertional heat stroke (EHS) collapsed at the end of a race. An athletic trainer (AT) assessed the patient, who presented with difficulty breathing then other signs of EHS (i.e. confusion, agitation). The patient was taken to the medical area, draped with a towel, and a rectal temperature (Tre) of 106.9°F(41.6°C) was obtained. The emergency action plan was activated and emergency medical services (EMS) were called. The patient was submerged in a cold-water immersion tub until EMS arrived (~15 minutes; Tre = 100.1°F; cooling rate: 0.41°F·min−1[0.25°C·min−1]). At the hospital, the patient received intravenous fluids, and urine and blood tests were normal. The patient was not admitted and returned to running without sequelae. Following best practices, AT's in secondary schools can prevent death from EHS by properly recognizing EHS and providing rapid cooling before transport.
... It was originally created to maintain heat safety amongst American military members during basic training drills (Yaglou and Minard 1956) but has become increasingly popular in other technical applications of heat safety. For example, in athletics, some American high schools have implemented WBGT-based thresholds for safe American football practice and play (Grundstein et al. 2015) while FIFA, soccer's governing body, uses WBGT guidelines for determining required water breaks during matches (Mountjoy et al. 2012). The National Institute for Occupational Safety and Health (NIOSH) uses the WBGT to ensure safe working conditions in extreme heat (Jacklitsch et al. 2016). ...
... While the WBGT performs just as well if not better than the HI in predicting heat stress compensability, it has primarily been used in determining thermal safety in athletic competitions (Grundstein et al. 2015) and industrial settings (Jacklitsch et al. 2016). Unlike the HI, the general public has little familiarity with WBGT and its uses. ...
Article
Multiple thermal indices have been created to categorize the impact of the ambient environment on human physiology and health. Many of these indices promulgate thresholds that are used to delineate between safe and unsafe thermal environments at rest and during physical activity (exercise, sport, industry, etc.). While some of these thresholds were empirically derived, others were established based on models or theoretical construct with no objective physiological measurements or rationale. In a world where heat is already the leading weather-related cause of death and climate change will exacerbate the effects of extreme heat in the future, it is important to determine if commonly used indices and associated thresholds are able to accurately describe ambient conditions which are thermally safe or unsafe. One physiologically- and biophysically-determined definition of safe environments is based on the upper limit of thermal balance (PSU H.E.A.T. Project). In the present study, young, healthy adults were exposed to a progressive heat stress protocol in an environmental chamber in both hot-dry and warm-humid conditions to determine critical environmental limits of dry-bulb temperature and vapor pressure which could then be compared to other widely used critical heat stress index values. That is, upper environmental limits for human heat balance were compared to common heat stress indices, including wet-bulb temperature (Twb), Heat Index (HI), Wet Bulb Globe Temperature (WBGT), and Universal Thermal Comfort Index (UTCI). Under activities of daily living, HI and WBGT thresholds very nearly match up with heat stress compensability curves based on critical heat balance limits while large variation was found in with UTCI. Interestingly, the theorized Twbthreshold of 35°C, used increasingly by mainstream media sources in describing extreme heat, was significantly higher than the critical limit for heat stress compensability. This work highlights the need for continued empirical work in determining and validating existing critical heat stress index thresholds as well as the need for better communication to the general public of what each heat stress index means for their environmental health and safety in a warming world.
... It was originally created to maintain heat safety amongst American military members during basic training drills (Yaglou and Minard 1956) but has become increasingly popular in other technical applications of heat safety. For example, in athletics, some American high schools have implemented WBGT-based thresholds for safe American football practice and play (Grundstein et al. 2015) while FIFA, soccer's governing body, uses WBGT guidelines for determining required water breaks during matches (Mountjoy et al. 2012). The National Institute for Occupational Safety and Health (NIOSH) uses the WBGT to ensure safe working conditions in extreme heat (Jacklitsch et al. 2016). ...
... While the WBGT performs just as well if not better than the HI in predicting heat stress compensability, it has primarily been used in determining thermal safety in athletic competitions (Grundstein et al. 2015) and industrial settings (Jacklitsch et al. 2016). Unlike the HI, the general public has little familiarity with WBGT and its uses. ...
Article
Full-text available
Extreme heat events and consequent detrimental heat-health outcomes have been increasing in recent decades and are expected to continue with future climate warming. While many indices have been created to quantify the combined atmospheric contributions to heat, few have been validated to determine how index-defined heat conditions impact human health. However, this subset of indices is likely not valid for all situations and populations nor easily understood and interpreted by health officials and the public. In this study, we compare the ability of thresholds determined from the National Weather Service’s (NWS) Heat Index (HI), the Wet Bulb Globe Temperature (WBGT), and the Universal Thermal Climate Index (UTCI) to predict the compensability of human heat stress (upper limits of heat balance) measured as part of the Pennsylvania State University’s Heat Environmental Age Thresholds (PSU HEAT) project. While the WBGT performed the best of the three indices for both minimal activities of daily living (MinAct; 83 W · m ⁻² ) and light ambulation (LightAmb; 133 W · m ⁻² ) in a cohort of young, healthy subjects, HI was likewise accurate in predicting heat stress compensability in MinAct conditions. HI was significantly correlated with subjects’ perception of temperature and humidity as well as their body core temperature, linking perception of the ambient environment with physiological responses in MinAct conditions. Given the familiarity the public has with HI, it may be better utilized in the expansion of safeguard policies and the issuance of heat warnings during extreme heat events, especially when access to engineered cooling strategies is unavailable.
... Nevertheless, when the WBGT ranges between 30.1 and 32.3, 28.8-31.0, and 26.8-29.0°C in hot, moderate, and mild climates, intensive exercise should be limited and the exposure to heat and humidity should be reduced [54]. In Japan, the WBGT was adopted to inform people of heat illness prevention, and the thermal environment becomes dangerous when the WBGT reaches 31.0°C. ...
... Indicators and different grades of heat stress and human thermal comfort.Regional heat safety guidelines for low-risk acclimatized individuals based on American College of Sports Medicine guidelines, WBGT[54] ...
Article
Many cities are facing urban heat problems, the combined effect of heatwaves under global climate change, and local warming associated with urbanization, resulting in severe environmental, economic, social, and health impacts. It is urgent to address urban heat problems. Existing studies indicate buildings are an important cause of urban heat, while buildings are favorable spaces to address urban heat problems through built environment decarbonization and the implementation of urban cooling strategies. Green building (GB) which has been recognized as an innovative philosophy and practice in the building sector, is proposed to address urban heat challenges. However, existing studies have offered a limited understanding of GB-based urban heat mitigation and adaptation. Therefore, this study aims to examine how the GBs contribute to urban heat mitigation and adaptation. In particular, this study analyses the contribution of buildings to urban heat problems in aspects of carbon emissions and the extensive urban modifications towards artificial landscapes and discusses the possible impacts caused by urban heat problems. Afterward, this study develops the framework of GB’s responses to urban heat problems in global warming mitigation, local warming mitigation, and urban heat adaptation. Based on this, such responses are analyzed in aspects of site planning, outdoor environments, transportation, building design, energy efficiency, water efficiency, material efficiency, indoor environmental quality, operation management, construction, and maintenance following the whole life cycle perspective. This paper helps understand how GB techniques contribute to urban heat mitigation and adaptation and provides a reference to the revision of the GB assessment system for addressing urban heat problems.
... A secondary analysis was conducted to evaluate if heatsafety region was associated with the health belief model constructs. Respondents provided their zip codes, which we used to determine their heat-safety region as defined by Grundstein et al. 28 Each health belief model construct consisted of 3 questions. A median value for the Likert scale was calculated for each participant and for each construct (see ''Reliability Analysis'' subsection). ...
Article
Context: Health care providers, including athletic trainers (ATs), may not be using the best practices for diagnosing exertional heat stroke (EHS), including rectal thermometry. Therefore, patients continue to be susceptible to death from EHS. Objective: To examine the health belief model and its association with using rectal thermometry as the best practice for diagnosing EHS. Design: Cross-sectional study. Setting: Web-based survey. Patients or other participants: A total of 208 secondary school ATs completed an online survey, and the data of 159 were included in the analysis. Main outcome measure(s): The survey contained 2 primary sections: AT characteristics and health belief model structured questions assessing perceptions and techniques used to diagnose EHS. Answers to the latter questions were rated on a 5-point Likert scale. We performed binary logistic regression to ascertain the effects of the health belief model constants (eg, perceived susceptibility, barriers), age, sex, and the type of school at which the AT worked on the likelihood that participants would use best practice for diagnosing patients with EHS. Results: Only 33.3% (n = 53) of the participating ATs reported they used best practice, including rectal thermometers to obtain core body temperature. The binary logistic regression was different for the 5 constructs: perceived susceptibility (\chi _6^2 = 22.30, P = .001), perceived benefits (\chi _6^2 = 71.79, P < .001), perceived barriers (\chi _6^2 = 111.22, P < .001), perceived severity (\chi _6^2 = 56.27, P < .001), and self-efficacy (\chi _6^2 = 64.84, P < .001). Analysis of these data showed that older ATs were at greater odds (P ≤ .02) of performing best practice. Conclusions: These data suggested that the health belief model constructs were associated with the performance of best practice, including using rectal thermometry to diagnose EHS. Researchers should aim to create tailored interventions based on health behavior to improve the adoption of best practice.
... See details at: https://www.weather.gov/rah/WBGT[20], and Grundstein et al.[21]. ...
Article
Full-text available
Current methods for estimating heat vulnerability of young athletes use a heat index (HI) or a wet bulb globe thermometer (WBGT), neither of which fully include the environmental or physiological characteristics that can affect a person's heat budget, particularly where activity occurs on a synthetic surface. This study analyzed and compared the standard methods, HI and WBGT, with a novel and more comprehensive method termed COMFA-Kid (CK) which is based on an energy budget model explicitly designed for youth. The COMFA model was presented at the same time to demonstrate the difference between a child and an adult during activity. Micrometeorological measurements were taken at a synthetic-surfaced football field during midday in hot environmental conditions. Standard methods (HI and WBGT) indicated that conditions on the field were relatively safe for youth to engage in activities related to football practice or games, whereas the CK method indicated that conditions were dangerously hot and could lead to exertional heat illness. Estimates using the CK method also indicated that coaches and staff standing on the sidelines, and parents sitting in the stands, would not only be safe from heat but would be thermally comfortable. The difference in thermal comfort experienced by coaches and staff off the field, versus that experienced by young players on the field, could affect decision making regarding the duration and intensity of practices and time in the game. The CK method, which is easy to use and available for modification for specific conditions, would lead to more accurate estimates of heat safety on outdoor synthetic surfaces in particular, and in sports with a high prevalence of heat illness such as football, and should be considered as a complementary or alternative preventive measure against heat.
... For an ongoing or expected heatwave event, it is crucial to estimate its risk or risk level that is magnitude of risk categorized by a metric table for prediction and real-time monitoring to mitigate its impact (Bobb et al., 2011;Lowe et al., 2011). In addition, the risk or risk level of future heat-related stress events for outdoor activities should be estimated to plan appropriate work times (Grundstein et al., 2015). It is, however, difficult to construct a heat-related risk assessment model to assess the impact on mortality because of the complexities associated with the relevant factors, such as meteorological, demographical, behavioral, and regional factors, as well as data availability (Medina-Ramón and Schwartz, 2007;Gascon et al., 2016;Son et al., 2016;Kim and Kim, 2017). ...
Article
Full-text available
The risk levels of heat-related extreme events need to be estimated for prediction and real-time monitoring to mitigate their impacts on air quality, public health, the ecosystem, and critical infrastructure. Many countries have adopted meteorological variable base thresholds for assessing the risk level of heat-related extreme events. These thresholds provide an approximate risk level for a specific event but do not consider its intensity and duration in the risk assessment. The current study provides a statistical tool to assess the risk of heat-related extreme events while concurrently considering their intensities and durations based on the wet-bulb globe temperature (WBGT). To this end, the intensity–duration–frequency (IDF) relationship of the extreme WBGT in South Korea was derived. Regional frequency analysis was employed to understand the IDF relationship. Return levels of heat-related extreme events in South Korea were calculated and their characteristics were investigated based on the annual maximum WBGT observations. The results showed that the IDF relationship could provide the risks of heat-related extreme events while concurrently considering their intensities and durations. The extreme WBGT in South Korea was used to categorize two regions such as coastal and inland based on their statistical characteristics. The return levels of the annual maximum WBGT events were found to vary largely by location. The return levels corresponding to 32 °C with 3-hour duration for stations in the coastal and inland regions ranged from 1- to 100-years and 3- to 1,000-years, respectively. Mean values of return levels for heatwave events in Seoul, Incheon, Daejon, Gwangju, Daegu, and Busan were 2.8-, 8.4-, 15.3-, 2.8-, 1.6-, and 2.2-years, respectively. The return levels of heatwaves for the warmer cities are smaller than those for cooler cities. The return levels of the heatwave events in South Korea showed a significant increasing trend in several cities, supporting the notion that the impact of heatwave events on South Korea might become more severe in the future.
... 9 Yet athletes in cooler areas may be more susceptible to sudden heat waves due to a lack of acclimatization to unusually intense conditions. 35 Preferably, clinicians will use regionspecific activity-modification guidelines. 36 Grundstein et al 35 developed regional-specific heat-safety guidelines based on local climate patterns in an attempt to standardize heat acclimatization across the country. ...
Article
Objective First, we will update recommendations for the prehospital management and care of patients with exertional heat stroke (EHS) in the secondary school setting. Second, we provide action items to aid clinicians in developing best-practice documents and policies for EHS. Third, we provide practical strategies clinicians can use to implement best practice for EHS in the secondary school setting. Data Sources An interdisciplinary work group of scientists, physicians, and athletic trainers evaluated the current literature regarding the prehospital care of EHS patients in secondary schools and developed this narrative review. When published research was nonexistent, expert opinion and experience guided the development of recommendations for implementing life-saving strategies. The workgroup evaluated and further refined the action-oriented recommendations using the Delphi method. Conclusions Exertional heat stroke continues to be a leading cause of sudden death in young athletes and the physically active. This may be partly due to the numerous barriers and misconceptions about the best practice for diagnosing and treating patients with EHS. Exertional heat stroke is survivable if it is recognized early and appropriate measures are taken before patients are transported to hospitals for advanced medical care. Specifically, best practice for EHS evaluation and treatment includes early recognition of athletes with potential EHS, a rectal temperature measurement to confirm EHS, and cold-water immersion before transport to a hospital. With planning, communication, and persistence, clinicians can adopt these best-practice recommendations to aid in the recognition and treatment of patients with EHS in the secondary school setting.
... reschedule or cancel) an event is based on the WBGT index developed by the United States Military and popularized by the American College of Sports Medicine (137). These athletic activity recommendations were recently extended in the US to include regional heat safety thresholds based on geographical variations in heat exposure and acclimatization status ( Table 3.3) (138). The majority of the recommendations are centered on activity modifications to undertake during training, based on adjusting exercise intensity and duration, work-to-rest ratios, and clothing or equipment worn (55). ...
Chapter
Exertional heat illnesses constitute an array of medical conditions comprising mild (heat syncope, heat rashes, exercise-associated muscle cramping, and heat exhaustion) to life-threatening disorders (exertional heat stroke). It is imperative that individuals, practitioners, and policymakers are well informed about the risk of and predisposing factors to exertional heat illnesses. Primary among these risk factors is heat stress which is the result of the combined effects of protective equipment or clothing, metabolic rate, and environmental conditions. Heat stress is a known hazard to both physical performance and health (e.g., exertional heat illness risk). Modifiable and non-modifiable risk factors are discussed as well as preventative strategies to mitigate the influence of heat stress and exertional heat illness risk.
... Temperature thresholds for locations in the mid-latitudes were lower. In the southern part of the US, classified as the warmest region in the country [53], temperatures above 28 • C increased mortality [16]. The thresholds were much lower for Hubei [40], Jiangsu [20], and Tibet [39] provinces of China. ...
Article
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Most epidemiological studies of high temperature effects on mortality have focused on urban settings, while heat-related health risks in rural areas remain underexplored. To date there has been no meta-analysis of epidemiologic literature concerning heat-related mortality in rural settings. This study aims to systematically review the current literature for assessing heat-related mortality risk among rural populations. We conducted a comprehensive literature search using PubMed, Web of Science, and Google Scholar to identify articles published up to April 2018. Key selection criteria included study location, health endpoints, and study design. Fourteen studies conducted in rural areas in seven countries on four continents met the selection criteria, and eleven were included in the meta-analysis. Using the random effects model, the pooled estimates of relative risks (RRs) for all-cause and cardiovascular mortality were 1.030 (95% CI: 1.013, 1.048) and 1.111 (95% CI: 1.045, 1.181) per 1 °C increase in daily mean temperature, respectively. We found excess risks in rural settings not to be smaller than risks in urban settings. Our results suggest that rural populations, like urban populations, are also vulnerable to heat-related mortality. Further evaluation of heat-related mortality among rural populations is warranted to develop public health interventions in rural communities.
... Tables 1 and 2 summarizes typical environmental conditions found among a range of sports into three distinct categories, and how these conditions contribute to the considerations around an individualized fluid plan. Of course, there are large regional differences in environmental conditions experienced for sports at the same time of year [45]. Local measurements utilizing WBGT allow for the greatest characterization of the environmental demands placed on athletes during exercise in the heat [46]. ...
Article
Full-text available
Personalized hydration strategies play a key role in optimizing the performance and safety of athletes during sporting activities. Clinicians should be aware of the many physiological, behavioral, logistical and psychological issues that determine both the athlete’s fluid needs during sport and his/her opportunity to address them; these are often specific to the environment, the event and the individual athlete. In this paper we address the major considerations for assessing hydration status in athletes and practical solutions to overcome obstacles of a given sport. Based on these solutions, practitioners can better advise athletes to develop practices that optimize hydration for their sports.
... Heat strain is further exacerbated in sports such as American football where protective equipment covers approximately 75% of body surface area, further limiting heat dissipation from the body (Armstrong et al., 2010). By altering work-to-rest ratios, including the extent of protective equipment that can be worn, based on regional environmental conditions, individuals are better protected from environmental extremes Casa et al., 2015;Grundstein, Hosokawa, & Casa, 2018;Grundstein, Williams, Phan, & Cooper, 2015). ...
Article
Exertional heat stroke (EHS) is a medical emergency whose likelihood in sport settings is often contingent on environmental factors, team policies, coaching strategies, and broader cultural expectations. Moreover, when it occurs, it requires immediate recognition, proper management, and care to optimize chances of survival or recovery without long-term sequelae. Max Gilpin, a secondary school American football player from Louisville, Kentucky, suffered an EHS during a football practice in August 2008, an event that resulted in his death. The purpose of this article is to use interdisciplinary methods to identify key factors that contributed to this tragedy so that similar situations do not happen again. It concludes that within a culture of inclusive gender norms and care, efforts should be made to have appropriate onsite medical expertise available to develop and implement best practices for the prevention, management, and treatment of EHS, along with coaching education specific to medical emergencies in sport and physical activity (such as EHS). This will create an environment that promotes health and safety for all student athletes participating in sport at the secondary school level.
... It is recommended that at a WBGT of ~29°C to 33°C, physical activity should be limited to 1 hour with 20 minutes of rest breaks distributed throughout. 12 The four 5-minute bouts at 35% represented this active rest time. Exercise and performance testing was terminated if one of the following criteria was met: (1) T rec reached 40°C, (2) participant requested to stop, (3) participant exhibited altered or uneven gait, or (4) HR was greater than estimated HR max for 5 minutes. ...
Article
Full-text available
Background: While increased face mask use has helped reduce COVID-19 transmission, there have been concerns about its influence on thermoregulation during exercise in the heat, but consistent, evidence-based recommendations are lacking. Hypothesis: No physiological differences would exist during low-to-moderate exercise intensity in the heat between trials with and without face masks, but perceptual sensations could vary. Study design: Crossover study. Level of evidence: Level 2. Methods: Twelve physically active participants (8 male, 4 female; age = 24 ± 3 years) completed 4 face mask trials and 1 control trial (no mask) in the heat (32.3°C ± 0.04°C; 54.4% ± 0.7% relative humidity [RH]). The protocol was 60 minutes of walking and jogging between 35% and 60% of relative VO2max. Rectal temperature (Trec), heart rate (HR), temperature and humidity inside and outside of the face mask (Tmicro_in, Tmicro_out, RHmicro_in, RHmicro_out) and perceptual variables (rating of perceived exertion (RPE), thermal sensation, thirst sensation, fatigue level, and overall breathing discomfort) were monitored throughout all trials. Results: Mean Trec and HR increased at 30- and 60-minute time points compared with 0-minute time points, but no difference existed between face mask trials and control trials (P > 0.05). Mean Tmicro_in, RHmicro_in, and humidity difference inside and outside of the face mask (ΔRHmicro) were significantly different between face mask trials (P < 0.05). There was no significant difference in perceptual variables between face mask trials and control trials (P > 0.05), except overall breathing discomfort (P < 0.01). Higher RHmicro_in, RPE, and thermal sensation significantly predicted higher overall breathing discomfort (r2 = 0.418; P < 0.01). Conclusion: Face mask use during 60 minutes of low-to-moderate exercise intensity in the heat did not significantly affect Trec or HR. Although face mask use may affect overall breathing discomfort due to the changes in the face mask microenvironment, face mask use itself did not cause an increase in whole body thermal stress. Clinical relevance: Face mask use is feasible and safe during exercise in the heat, at low-to-moderate exercise intensities, for physically active, healthy individuals.
... As a result, the mean WBGT was 23.8°C, with the start of practice tending to be warmer (;27°C) compared with the end of practice (;22°C). Based on regional heat safety guidelines, the conditions in which the practices occurred would not have warranted any practice modifications due to these environmental conditions (16). This study was not without limitations. ...
Article
Lopez, RM, Ashley, CD, Zinder, SM, and Tritsch, AJ. Thermoregulation and hydration in female American football players during practices. J Strength Cond Res XX(X): 000-000, 2019-Little is known about hydration practices and thermoregulation in female tackle football players. The purpose of the study was to examine the thermoregulatory and hydration responses of female professional American football players. Fifteen females from the same tackle football team volunteered for this observational field study. Each subject was observed for 4 practices for the following measures: gastrointestinal temperature (TGI), maximum TGI, heart rate (HR), maximum HR (HRmax), fluid consumption, sweat rate, percent body mass loss (%BML), urine specific gravity (USG), urine color (Ucol), perceptual measures of thirst, thermal sensations, and rating of perceived exertion (RPE). Descriptive data (mean ± SD) were calculated for all measures. Main measures were analyzed using a repeated-measures analysis of variance. Trials took place during evening practices. Average TGI during practices was 38.0 ± 0.3° C while maximum TGI was 38.4 ± 0.3° C (n = 14). Average practice HR was 118 ± 11 b·min, while HRmax was 148 ± 13 b·min. Subjects arrived at practices with Ucol of 3 ± 1 and USG of 1.018 ± 0.007. Postpractice USG (1.022 ± 0.007) was significantly higher than prepractice across all days (p < 0.001). The average sweat rate across 4 practices was 0.6 ml·h. Average %BML was 0.3 ± 0.4%. Thirst and thermal sensations were moderate (4 ± 1 and 5 ± 1, respectively), while RPE was 11 ± 1. Female football players tended to have similar physiological responses to males. Although subjects seemed to adequately match their sweat losses with fluid consumed during practice, there was considerable variability in hydration indices and hydration habits, with some subjects experiencing hypohydration and others overestimating their fluid needs. Those working with this population should emphasize the need for hydration education and establish individualized hydration regimens.
... Assessment of outdoor thermal environments for humans can provide meaningful information for addressing economic and social issues and related challenges, including outdoor activity (Grundstein et al., 2015), tourism (Li and Chi, 2014), planning of cities and urban design (Gascon et al., 2016), energy conservation (Yang et al., 2014), and public health . Moreover, there is consensus for the acknowledgement of climate change in scientific communities (Byrne and O'Gorman, 2016;Byrne and O'Gorman, 2018;Lorenz and DeWeaver, 2007;Trenberth and Josey, 2007;Vicente-Serrano et al., 2018). ...
Article
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Changes of thermal environment can lead to unfavorable impacts such as a decrease of thermal stratification, increase of energy consumption, and increase of thermal health risk. Investigating changes in outdoor thermal environments can provide meaningful information for addressing economic and social issues and related challenges. In this study, thermal environment changes in South Korea were investigated using a nonstationary two-component Gaussian mixture model (NSGMM) for air temperature and two thermal comfort indices. For this, the perceived temperature (PT) and universal thermal climate index (UTCI) were employed as the thermal comfort index. Thermal comfort indices were computed using observed meteorological data at 26 weather stations for 37 years in South Korea. Meanwhile, trends of thermal comforts in the warm and cool seasons were simultaneously modeled by the NSGMM. The results indicate significant increasing trends in thermal comfort indices for South Korea. The increasing trends in thermal comfort indices both the warm and cool seasons were detected while the magnitudes of the trends are significantly different. This difference between the magnitude of trends led to an increase in mean and inter-annual variability of thermal comfort indices based on PT, while an increase of mean and decrease of inter-annual variability were observed based on the UTCI. Moreover, the annual proportion of the category referring to days in comfort based on the results of PT has decreased due to the different trends of thermal comfort indices in the warm and cool seasons. This decrease may lead to an increase of thermal health risk that is larger than what would be expected from the results considering the increasing trend of the annual mean temperature in South Korea. From this result, it can be inferred that the thermal health risk in South Korea may be more adverse than what we originally expected from the current temperature trend.
... In addition, the aforementioned environment-based activity modifications should be established using regional environmental conditions as these are more appropriate given the climatic variability observed over various geographical locations (1,12,31). For example, a secondary school student athlete participating in a sport, such as American football, would experience vastly different environmental conditions if they were living in Northwest Washington as compared to Florida. ...
Article
Exertional heat stroke (EHS) remains one of the leading causes of sudden death in sport despite clear evidence showing 100% survivability with the proper standards of care in place and utilized. Of particular concern are student athletes competing at the secondary school level, where the extent of appropriate health care services remains suboptimal compared with organized athletics at the collegiate level and higher. While rapid recognition and rapid treatment of EHS ensures survival, the adoption and implementation of these lifesaving steps within secondary school athletics warrant further discussion within the sports medicine community. Establishing proper policies regarding the prevention and care of EHS coupled with utilizing an interdisciplinary care approach is essential for 1) minimizing risk and 2) guaranteeing optimal outcomes for the patient.
... The National Solar Radiation Database (NSRDB) that produced the National Renewable Energy Laboratory (NREL 2012) provides a serially complete dataset of meteorological variables, including solar radiation at locations throughout the USA and in selected regions internationally. This dataset has been previously used to run the Liljegren model to produce long-term times series of WBGT across the contiguous USA (e.g., Grundstein et al. 2014Grundstein et al. , 2015. Reanalysis datasets such as the second modern-era retrospective analysis for research and applications (MERRA-2) may also provide viable sources of input data (Gelaro et al. 2017). ...
Article
Full-text available
Exertional heat illnesses affect thousands of athletes each year and are a leading cause of death in sports. The wet bulb globe temperature (WBGT) is widely used as a heat stress metric in athletics for adjusting activities. The WBGT can be measured on-site with portable sensors, but instrument cost may provide a barrier for usage. Modeling WBGT from weather station data, then, presents an affordable option. Our study compares two WBGT models of varying levels of sophistication: the Australian Bureau of Meteorology (ABM) model which uses only temperature and humidity as inputs and a physically based model by Liljegren that incorporates temperature, humidity, wind speed, and solar radiation in determining WBGT outputs. The setting for the study is 19 University of Georgia Weather Network stations selected from across the state of Georgia, USA, over a 6-year period (2008–2014) during late summer and early fall months. Results show that the ABM model’s performance relative to the Liljegren model varies based on time of day and weather conditions. WBGTs from the ABM model are most similar to those from the Liljegren model during midday when the assumption of moderately high sun most frequently occurs. We observed increasingly large positive biases with the ABM model both earlier and later in the day during periods with lower solar radiation. Even during midday, large (≥ 3 °C) underestimates may occur during low wind conditions and overestimates during periods with high cloud cover. Such differences can lead to inaccurate activity modification and pose dangers for athletes either by underestimating heat-related hazards or by imposing an opportunity cost if practice activities are limited by overestimating the heat hazard.
... However, even ISO7243 and ACGIH-TLV, which are international representative standards for heat stroke, only target healthy and physically suitable workers, and do not take regional or age differences into account. Grundstein [39] has proposed a heat standard that considers the level of heat acclimatization of each region. In the USA, the 90th percentile of the DMW in summer varies from 36 °C or higher to 26 °C or lower depending on each region, so heat acclimatization also differs. ...
Article
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Background Although age and regional climate are considered to have effects on the incidence ratio of heat-related illness, quantitative estimation of age or region on the effect of occurring temperature for heat stroke is limited. Methods By utilizing data on the number of daily heat-related ambulance transport (HAT) in each of three age groups (7–17, 18–64, 65 years old, or older) and 47 prefectures in Japan, and daily maximum temperature (DMT) or Wet Bulb Globe Temperature (DMW) of each prefecture for the summer season, the effects of age and region on heat-related illness were studied. Two-way ANOVA was used to analyze the significance of the effect of age and 10 regions in Japan on HAT. The population-weighted average of DMT or DMW measured at weather stations in each prefecture was used as DMT or DMW for each prefecture. DMT or DMW when HAT is one in 100,000 people (T 1 and W 1 , respectively) was calculated for each age category and prefecture as an indicator of heat acclimatization. The relation between T 1 or W 1 and average DMT or DMW of each age category and prefecture were also analyzed. Results HAT of each age category and prefecture was plotted nearly on the exponential function of corresponding DMT or DMW. Average R ² of the regression function in 47 prefectures in terms of DMW was 0.86, 0.93, and 0.94 for juveniles, adults, and elderly, respectively. The largest regional difference of W 1 in 47 prefectures was 4.5 and 4.8 °C for juveniles and adults, respectively between Hokkaido and Tokyo, 3.9 °C for elderly between Hokkaido and Okinawa. Estimated W 1 and average DMT or DMW during the summer season for 47 prefectures was linearly related. Regarding age difference, the regression line showed that W 1 of the prefecture for DMW at 30 °C of WBGT was 31.1 °C, 32.4 °C, and 29.8 °C for juveniles, adults, and elderly, respectively. Conclusions Age and regional differences affected the incidence of HAT. Thus, it is recommended that public prevention measures for heat-related disorders take into consideration age and regional variability.
... [2][3][4] The WBGT is an index that integrates the influences of multiple meteorologic variables that can affect heat stress and is used to determine the need for activity modification in the heat for athletes, the military, and other workers. [5][6][7][8] The American College of Sports Medicine 2 suggested that O n l i n e F i r s t intense exercise be limited when the WBGT exceeds 308C and that the risk of foreseeable uncompensable heat stress exists when the WBGT exceeds 32.38C, even among those who are heat acclimatized and physically fit. Although no exertional heat-stroke fatalities have been documented among elite football players during competition to date, exertional heat illness is one of the common injuries reported among youth and collegiate football players, especially during the summer and preseason months when the environmental conditions are warmer. ...
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Context: : Exposure to severe heat can have detrimental effects on athletic performance and increase the risk of exertional heat injuries. Therefore, proactive assessment of the environmental characteristics of international football match venues becomes critical in ensuring the safety and optimal performance of the athletes. Objective: : To propose the use of climatologic data (modeled wet-bulb globe temperature [WBGT]) in making athletic-event management decisions for the 2020 Summer Olympic Games and the 2022 Fédération Internationale de Football Association World Cup. Design: : Descriptive study. Setting: : Hourly meteorologic input data for a WBGT model were obtained from the second Modern-Era Retrospective Analysis for Research and Applications for Japan (Yokohama and Saitama) and Qatar (Doha and Al-Daayen). Main outcome measure(s): : The pattern of hourly WBGT and percentage of hours between 30°C and 32°C and exceeding 32°C WBGT during the expected competition periods for the 2020 Summer Olympic Games in Japan and the scheduled (November, December) and traditional (June, July) periods of the World Cup games in Qatar. Results: : The WBGT during the 2020 Olympic football tournament in Japan may exceed 30°C in 40% to 50% of the late mornings and early afternoons. The shift in tournament timing for the 2022 Fédération Internationale de Football Association World Cup in Qatar from the summer to late fall will reduce the exposure to ≥30°C WBGT to null. Conclusions: : Directors of mass sporting events should consider using climatologic data in their organizational decision making to assess the potential heat illness risk and to implement risk-mitigation plans.
... The fact that this case occurred in early October rather than during the preseason summer months highlights the importance of being prepared, regardless of the season or sport. In heat safety region 3, 19 it is important for clinicians to understand that a sudden rise in WBGT can increase the risk of EHS if the environmental conditions have previously been mild. The main intrinsic risk factor in this case was that the patient had experienced an upper respiratory infection in the preceding days. ...
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A 14-year-old female high school cross- country runner (height = 154 cm, mass = 48.1 kg) with no history of exertional heat stroke (EHS) collapsed at the end of a race. An athletic trainer assessed the patient, who presented with difficulty breathing and then other signs of EHS (eg, confusion and agitation). The patient was taken to the medical area and draped with a towel, and a rectal temperature (Tre) of 106.9°F (41.6°C) was obtained. The emergency action plan was activated, and emergency medical services was called. The patient was submerged in a cold-water immersion tub until emergency medical services arrived (∼15 minutes; Tre = 100.1°F; cooling rate: 0.41°F.min−1[0.25°C.min−1]). At the hospital, the patient received intravenous fluids, and urine and blood tests were normal. She was not admitted and returned to running without sequelae. Following best practices, secondary school athletic trainers can prevent deaths from EHS by properly recognizing the condition and providing rapid cooling before transport.
... As such, a "one-size-fits-all" activity modification policy may not be appropriate for all regions as it fails to recognize that typical conditions in a hotter climate may be considered extreme in a cooler climate (Grundstein et al. 2018). Guidelines based on regional climate conditions, then, would better identify locally extreme conditions (Grundstein et al. 2015;Grimmer et al. 2006). ...
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Chapter
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Background Although experts have advocated for regionally specific heat safety guidelines for decades, guidelines have not been universally adopted. Purpose To describe the rate and risk factors associated with exertional heat illness (EHI). Study Design Descriptive epidemiology study. Methods For a 3-month period (August-October) over 6 years (2013-2018), athletic trainers at 13 high schools in North Central Florida recorded varsity football practice time and length, wet-bulb globe temperature (WBGT), and incidences of EHI, including heat stroke, heat exhaustion, and heat syncope. Results Athletes sustained 54 total EHIs during 163,254 athlete-exposures (AEs) for the 3-month data collection periods over 6 years (incidence rate [IR], 3.31 /10,000 AEs). Heat exhaustion accounted for 59.3% (32/54), heat syncope 38.9% (21/54), and heat stroke 1.9% (1/54) of all EHIs recorded. Of the EHIs, 94.4% (51/54) were experienced within the first 19 practices. The first 19 practices had an IR of 7.48 of 10,000 AEs, and the remaining 44 practices had an IR of 0.32 of 10,000 AEs, demonstrating that the risk of EHI for practices 1 to 19 was 23.7 times that of the remaining practices. When comparing morning to afternoon practices, 35.2% (19/54) EHI incidents occurred during morning practices. The risk of EHI during practices with WBGT >82°F (27.8°C) was 3.5 times that of practices with WBGT <82°F. Conclusion In the current study, the risk of EHI was greatest in the first 19 practices of the season and during practices with WBGT >82°F. As modifiable risk factors for EHI, increased vigilance and empowerment to adhere to acclimatization guidelines can mitigate EHI risk. Health care providers must continue to advocate for implementation of regulations and the authority to make decisions to ensure patient safety.
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Exertional heat illness and stroke are serious concerns across youth and college sports programs. While some teams and governing bodies have adopted the wet bulb globe temperature (WBGT), few practitioners use measurements on the field of play; rather, they often rely on regionally modeled or estimated WBGT. However, urban development-induced heat and projected climate change increase exposure to heat. We examined WBGT levels between various athletic surfaces and regional weather stations under current and projected climates and in hot-humid and hot-dry weather regimes in the southwest U.S. in Tempe, Arizona. On-site sun-exposed WBGT data across five days (07:00–19:00 local time) in June (dry) and August (humid) were collected over five athletic surfaces: rubber, artificial turf, clay, grass, and asphalt. Weather stations data were used to estimate regional WBGT (via the Liljegren model) and compared to on-site, observed WBGT. Finally, projected changes to WBGT were modeled under mid-century and late-century conditions. On-field WBGT observations were, on average, significantly higher than WBGT estimated from regional weather stations by 2.4°C–2.5°C, with mean on-field WBGT across both months of 28.52.76°C (versus 25.83.21°C regionally). However, between-athletic surface WBGT differences were largely insignificant. Significantly higher mean WBGTs occurred in August (30.12.35°C) versus June (26.92.19°C) across all venues; August conditions reached ‘limit activity’ or ‘cancellation’ thresholds for 6–8 hours and 2–4 hours of the day, respectively, for all sports venues. Climate projections show increased WBGTs across measurement locations, dependent on projection and period, with average August WBGT under the highest representative concentration pathway causing all-day activity cancellations. Practitioners are encouraged to use WBGT devices within the vicinity of the fields of play, yet should not rely on weather station estimations without corrections used. Heat concerns are expected to increase in the future, underlining the need for athlete monitoring, local cooling design strategies, and heat adaptation for safety.
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Heat stress illnesses represent a rising public health threat; however, associations between environmental heat and observed adverse health outcomes across populations and geographies remain insufficiently elucidated to evaluate risk and develop prevention strategies. In particular, military-relevant large-scale studies of daily heat stress morbidity responses among physically active, working-age adults to various indices of heat have been limited. We evaluated daily means, maximums, minimums, and early morning measures of temperature, heat index, and wet bulb globe temperature (WBGT) indices, assessing their association with 31,642 case-definition heat stroke and heat exhaustion encounters among active duty servicemembers diagnosed at 24 continental US installations from 1998 to 2019. We utilized anonymized encounter data consisting of hospitalizations, ambulatory (out-patient) visits, and reportable events to define heat stress illness cases and select the 24 installations with the highest case counts. We derived daily indices of heat from hourly-scale gridded climate data and applied a case-crossover study design incorporating distributed-lag, nonlinear models with 5 days of lag to estimate odds ratios at one-degree increments for each index of heat. All indices exhibited nonlinear odds ratios with short-term lag effects throughout observed temperature ranges. Responses were positive, monotonic, and exponential in nature, except for maximum daily WBGT, minimum daily temperature, temperature at 0600 h (local), and WBGT at 0600 h (local), which, while generally increasing, showed decreasing risk for the highest heat category days. The risk for a heat stress illness on a day with a maximum WBGT of 32.2 °C (90.0 °F) was 1.93 (95% CI, 1.82 - 2.05) times greater than on a day with a maximum WBGT of 28.6 °C (83.4 °F). The risk was 2.53 (2.36-2.71) times greater on days with a maximum heat index of 40.6 °C (105 °F) compared to 32.8 °C (91.0 °F). Our findings suggest that prevention efforts may benefit from including prior-day heat levels in risk assessments, from monitoring temperature and heat index in addition to WBGT, and by promoting control measures and awareness across all heat categories.
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This study describes the impact of weather on human mortality at numerous locations around the United States. We evaluate forty-eight cities and determine the differential impact of weather on mortality on an intercity and interregional level. The mortality data are analyzed separately for different age, race, and cause of death categories. The possible impact of geographical and within-season acclimatization is also analyzed. Thresh-old temperatures, which represent the temperature beyond which mortality increases, are identified for all the categories and all cities in summer and winter. We correlate numerous weather variables with mortality for days with temperatures beyond the threshold. In summer, warm, humid, calm conditions (especially at night) relate to the highest mortality. The strongest relationships occur in regions where hot weather is uncommon and the weakest relationships in the hottest locales. Regional acclimatization appears to be especially important in summer. A strong intra-seasonal acclimatization factor is also apparent, and hot weather early in the season produces a more pronounced response than similar weather late in the season. Winter relationships are generally weaker, and cloudy, damp, snowy conditions are associated with the greatest mortality. In both seasons, the elderly appear to be disproportionately stressed when compared to other age groups. Racial responses appear similar on a national and seasonal level, but there are differential responses on a regional level. Non-whites appear more sensitive than whites in the South during both seasons.
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This article emphasizes significant recent advances regarding heat stress and its impact on exercise performance, adaptations, fluid electrolyte imbalances, and pathophysiology. During exercise-heat stress, the physiological burden of supporting high skin blood flow and high sweating rates can impose considerable cardiovascular strain and initiate a cascade of pathophysiological events leading to heat stroke. We examine the association between heat stress, particularly high skin temperature, on diminishing cardiovascular/aerobic reserves as well as increasing relative intensity and perceptual cues that degrade aerobic exercise performance. We discuss novel systemic (heat acclimation) and cellular (acquired thermal tolerance) adaptations that improve performance in hot and temperate environments and protect organs from heat stroke as well as other dissimilar stresses. We delineate how heat stroke evolves from gut underperfusion/ischemia causing endotoxin release or the release of mitochondrial DNA fragments in response to cell necrosis, to mediate a systemic inflammatory syndrome inducing coagulopathies, immune dysfunction, cytokine modulation, and multiorgan damage and failure. We discuss how an inflammatory response that induces simultaneous fever and/or prior exposure to a pathogen (e.g., viral infection) that deactivates molecular protective mechanisms interacts synergistically with the hyperthermia of exercise to perhaps explain heat stroke cases reported in low-risk populations performing routine activities. Importantly, we question the "traditional" notion that high core temperature is the critical mediator of exercise performance degradation and heat stroke. Published 2011 This article is a U.S. Government work and is in the public domain in the USA. Compr Physiol 1:1883-1928, 2011.
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In this paper, we review the epidemiological evidence on the relationship between ambient temperature and morbidity. We assessed the methodological issues in previous studies and proposed future research directions. DATA SOURCES AND DATA EXTRACTION: We searched the PubMed database for epidemiological studies on ambient temperature and morbidity of noncommunicable diseases published in refereed English journals before 30 June 2010. Forty relevant studies were identified. Of these, 24 examined the relationship between ambient temperature and morbidity, 15 investigated the short-term effects of heat wave on morbidity, and 1 assessed both temperature and heat wave effects. Descriptive and time-series studies were the two main research designs used to investigate the temperature-morbidity relationship. Measurements of temperature exposure and health outcomes used in these studies differed widely. The majority of studies reported a significant relationship between ambient temperature and total or cause-specific morbidities. However, there were some inconsistencies in the direction and magnitude of nonlinear lag effects. The lag effect of hot temperature on morbidity was shorter (several days) compared with that of cold temperature (up to a few weeks). The temperature-morbidity relationship may be confounded or modified by sociodemographic factors and air pollution. There is a significant short-term effect of ambient temperature on total and cause-specific morbidities. However, further research is needed to determine an appropriate temperature measure, consider a diverse range of morbidities, and to use consistent methodology to make different studies more comparable.
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Over the period 1980-2009, there were 58 documented hyperthermia deaths of American-style football players in the United States. This study examines the geography, timing, and meteorological conditions present during the onset of hyperthermia, using the most complete dataset available. Deaths are concentrated in the eastern quadrant of the United States and are most common during August. Over half the deaths occurred during morning practices when high humidity levels were common. The athletes were typically large (79% with a body mass index >30) and mostly (86%) played linemen positions. Meteorological conditions were atypically hot and humid by local standards on most days with fatalities. Further, all deaths occurred under conditions defined as high or extreme by the American College of Sports Medicine using the wet bulb globe temperature (WBGT), but under lower threat levels using the heat index (HI). Football-specific thresholds based on clothing (full football uniform, practice uniform, or shorts) were also examined. The thresholds matched well with data from athletes wearing practice uniforms but poorly for those in shorts only. Too few cases of athletes in full pads were available to draw any broad conclusions. We recommend that coaches carefully monitor players, particularly large linemen, early in the pre-season on days with wet bulb globe temperatures that are categorized as high or extreme. Also, as most of the deaths were among young athletes, longer acclimatization periods may be needed.
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To assess heat related mortalities in relation to climate within Europe. Observational population study. Setting: North Finland, south Finland, Baden-Württemberg, Netherlands, London, north Italy, and Athens. People aged 65-74. Main outcome measures: Mortalities at temperatures above, below, and within each region's temperature band of minimum mortality. Mortality was lowest at 14.3-17.3 degrees C in north Finland but at 22.7-25.7 degrees C in Athens. Overall the 3 degrees C minimum mortality temperature bands were significantly higher in regions with higher than lower mean summer temperatures (P=0.027). This was not due to regional differences in wind speeds, humidity, or rain. As a result, regions with hot summers did not have significantly higher annual heat related mortality per million population than cold regions at temperatures above these bands. Mean annual heat related mortalities were 304 (95% confidence interval 126 to 482) in North Finland, 445 (59 to 831) in Athens, and 40 (13 to 68) in London. Cold related mortalities were 2457 (1130 to 3786), 2533 (965 to 4101), and 3129 (2319 to 3939) respectively. Populations in Europe have adjusted successfully to mean summer temperatures ranging from 13.5 degrees C to 24.1 degrees C, and can be expected to adjust to global warming predicted for the next half century with little sustained increase in heat related mortality. Active measures to accelerate adjustment to hot weather could minimise temporary rises in heat related mortality, and measures to maintain protection against cold in winter could permit substantial reductions in overall mortality as temperatures rise.
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OBJECTIVE: To present recommendations for the prevention, recognition, and treatment of exertional heat illnesses and to describe the relevant physiology of thermoregulation. BACKGROUND: Certified athletic trainers evaluate and treat heat-related injuries during athletic activity in "safe" and high-risk environments. While the recognition of heat illness has improved, the subtle signs and symptoms associated with heat illness are often overlooked, resulting in more serious problems for affected athletes. The recommendations presented here provide athletic trainers and allied health providers with an integrated scientific and practical approach to the prevention, recognition, and treatment of heat illnesses. These recommendations can be modified based on the environmental conditions of the site, the specific sport, and individual considerations to maximize safety and performance. RECOMMENDATIONS: Certified athletic trainers and other allied health providers should use these recommendations to establish on-site emergency plans for their venues and athletes. The primary goal of athlete safety is addressed through the prevention and recognition of heat-related illnesses and a well-developed plan to evaluate and treat affected athletes. Even with a heat-illness prevention plan that includes medical screening, acclimatization, conditioning, environmental monitoring, and suitable practice adjustments, heat illness can and does occur. Athletic trainers and other allied health providers must be prepared to respond in an expedient manner to alleviate symptoms and minimize morbidity and mortality.
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Serious heat illness has received considerable recent attention due to catastrophic heat waves in the United States and Europe, the deaths of high-profile athletes, and military deployments. This study documents heat illness hospitalizations and deaths for the U.S. Army from 1980 through 2002. Hospitalization data were obtained from the Total Army Injury Health Outcomes Database (TAIHOD) coded according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). North Atlantic Treaty Organization Standardization Agreement codes were searched for heat injuries in an effort to detect cases that were not found during the ICD-9-CM search. Five-thousand two-hundred forty-six soldiers were hospitalized, and 37 died due to heat illness. Our results indicate: 1) approximately 60% reduction in hospitalization rates (fewer heat exhaustion cases) over the 22-yr period; 2) fivefold increase in heat stroke hospitalization rates (1.8 per 100,000 in 1980 to 14.5 per 100,000 in 2001); 3) heat stroke cases were associated with dehydration (17%), rhabdomyolysis (25%), and acute renal failure (13%); 4) lower hospitalizations rates among African and Hispanic Americans compared with Caucasians (incidence density ratio, 0.76 [95% confidence interval, 0.71-0.82]; 5) greater rates of hospitalizations and heat strokes among recruits from northern than southern states (incidence density ratio, 1.69 [95% confidence interval, 1.42-1.90]; and 6) greater rates of hospitalizations and heat strokes among women than men (incidence density ratio, 1.18 [95% confidence interval, 1.09-1.27]). Exertional heat illness continues to be a military problem during training and operations. Whereas the hospitalization rate of heat illness is declining, heat stroke has markedly increased.
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Context: Recommendations for heat illness prevention provided by sports medicine associations do not always account for sex differences, specific age populations, regional environmental conditions, equipment worn during activity, or the athlete's size or preexisting level of fitness. Objective: To evaluate the rate of exertional heat illness (EHI) among collegiate football athletes and to monitor environmental conditions during American football practice for a 3-month period. Design: Epidemiologic study in which we reviewed the occurrence rates of EHI and wet bulb globe temperature readings during a 3-month period of American collegiate football practice sessions. Setting: Five universities in the southeastern region of the United States. Patients or other participants: Collegiate football players at the 5 universities. Main outcome measure(s): Wet bulb globe temperatures were recorded from August through October 2003, at the beginning, middle, and end of each practice session. The EHIs were identified and recorded, and athlete-exposures (AEs) were calculated. Results: A total of 139 EHIs and 33 196 AEs were reported (EHI rate = 4.19/1000 AEs). The highest incidence of EHIs was in August (88%, EHI rate = 8.95/1000 AEs) and consisted of 70% heat cramps (6.13/1000 AEs), 23% heat exhaustion (2.06/ 1000 AEs), and 7% heat syncope (0.58/1000 AEs). No cases of heat stroke or hyponatremia were identified. The highest risk of EHI occurred during the first 3 weeks of the study; mean wet bulb globe temperature declined significantly as the study continued ( P < .001). Temperatures in the final 5 weeks of the study were significantly cooler than in the first 5 weeks ( P < .05). Conclusions: Heat cramps were the most common EHI and occurred most often during the first 3 weeks of practice. Athletic trainers should take all necessary preventive measures to reduce the risk of EHI.
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Exertional heat illness can affect athletes during high-intensity or long-duration exercise and result in withdrawal from activity or collapse during or soon after activity. These maladies include exercise associated muscle cramping, heat exhaustion, or exertional heatstroke. While certain individuals are more prone to collapse from exhaustion in the heat (i.e., not acclimatized, using certain medications, dehydrated, or recently ill), exertional heatstroke (EHS) can affect seemingly healthy athletes even when the environment is relatively cool. EHS is defined as a rectal temperature greater than 40 degrees C accompanied by symptoms or signs of organ system failure, most frequently central nervous system dysfunction. Early recognition and rapid cooling can reduce both the morbidity and mortality associated with EHS. The clinical changes associated with EHS can be subtle and easy to miss if coaches, medical personnel, and athletes do not maintain a high level of awareness and monitor at-risk athletes closely. Fatigue and exhaustion during exercise occur more rapidly as heat stress increases and are the most common causes of withdrawal from activity in hot conditions. When athletes collapse from exhaustion in hot conditions, the term heat exhaustion is often applied. In some cases, rectal temperature is the only discernable difference between severe heat exhaustion and EHS in on-site evaluations. Heat exhaustion will generally resolve with symptomatic care and oral fluid support. Exercise associated muscle cramping can occur with exhaustive work in any temperature range, but appears to be more prevalent in hot and humid conditions. Muscle cramping usually responds to rest and replacement of fluid and salt (sodium). Prevention strategies are essential to reducing the incidence of EHS, heat exhaustion, and exercise associated muscle cramping.
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Episodes of extremely hot or cold temperatures are associated with increased mortality. Time-series analyses show an association between temperature and mortality across a range of less extreme temperatures. In this paper, the authors describe the temperature-mortality association for 11 large eastern US cities in 1973-1994 by estimating the relative risks of mortality using log-linear regression analysis for time-series data and by exploring city characteristics associated with variations in this temperature-mortality relation. Current and recent days' temperatures were the weather components most strongly predictive of mortality, and mortality risk generally decreased as temperature increased from the coldest days to a certain threshold temperature, which varied by latitude, above which mortality risk increased as temperature increased. The authors also found a strong association of the temperature-mortality relation with latitude, with a greater effect of colder temperatures on mortality risk in more-southern cities and of warmer temperatures in more-northern cities. The percentage of households with air conditioners in the south and heaters in the north, which serve as indicators of socioeconomic status of the city population, also predicted weather-related mortality. The model developed in this analysis is potentially useful for projecting the consequences of climate-change scenarios and offering insights into susceptibility to the adverse effects of weather.
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American Football players are among the most susceptible athletes to heat-related illnesses. Environmental conditions are an important factor when considering risk rates for these illnesses. Thus, we examine the spatio-temporal variations in the wet bulb globe temperature (WBGT), a commonly used metric for heat exposure, and quantify the hazard for extreme heat using safety thresholds specifically derived for athletes from the American College of Sports Medicine (ACSM). The objective is to provide better information on heat-related hazards to help mitigate the risk of exertional heat illnesses (EHI) among football players. We created a unique 15-year climatology (1991–2005) of August WBGTs for 217 locations across the contiguous United States using weather station observations and a WBGT model. Thirteen 3-h overlapping training session times ranging from 6–9 a.m. to 6–9 p.m. were examined to identify how the WBGT varies with the time of day the practice session was held and how frequently the WBGT during those sessions posed a hazard for extreme heat by exceeding two ACSM safety thresholds (30.1 °C and 32.3 °C). Maximum hazards for extreme heat are located in an arc across the Southern tier of the country, stretching from eastern Texas through to South Carolina as well as across southern Arizona and southeastern California. Climatologically, practice sessions early in the morning and later in the evening were best for minimizing heat exposure while those held from late morning through afternoon, particularly the noon-3 p.m. and 1–4 p.m. periods, had the highest WBGT values and were the practice periods that most frequently exceeded safety thresholds. Delaying the start of afternoon practices a few hours, however, may substantially reduce the likelihood of oppressive conditions and reduce the risk for heat illnesses.
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Environmental heat illness and injuries are a serious concern for the Army and Marines. Currently, the Wet-Bulb Globe Temperature (WBGT) index is used to evaluate heat injury risk. The index is a weighted average of dry-bulb temperature (Tdb), black globe temperature (Tbg), and natural wet-bulb temperature (Tnwb). The WBGT index would be more widely used if it could be determined using standard weather instruments. This study compares models developed by Liljegren at Argonne National Laboratory and by Matthew at the U.S. Army Institute of Environmental Medicine that calculate WBGT using standard meteorological measurements. Both models use air temperature (Ta), relative humidity, wind speed, and global solar radiation (RG) to calculate Tnwb and Tbg. The WBGT and meteorological data used for model validation were collected at Griffin, Georgia and Yuma Proving Ground (YPG), Arizona. Liljegren (YPG: R(2) = 0.709, p < 0.01; Griffin: R(2) = 0.854, p < 0.01) showed closer agreement between calculated and actual WBGT than Matthew (YPG: R(2) = 0.630, p < 0.01; Griffin: R(2) = 0.677, p < 0.01). Compared to actual WBGT heat categorization, the Matthew model tended to underpredict compared to Liljegren's classification. Results indicate Liljegren is an acceptable alternative to direct WBGT measurement, but verification under other environmental conditions is needed.
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This report describes processes we have implemented to use global pyranometer-based estimates of mean radiant temperature as the common solar load input for the Scenario model, the USARIEM heat strain model, and for the computation of the solar radiation sensitive components of the Wet Bulb Globe Temperature (WBGT) index.
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It is estimated that more than 9000 high school athletes are treated for exertional heat illness annually. Risk factors include being obese and beginning practice during hot and humid weather, when athletes are not yet acclimated to physical exertion in heat. To describe the epidemiology of exertional heat illness in high school athletes. National High School Sports-Related Injury Surveillance System data (2005/2006-2010/2011) were analyzed in 2012 to calculate rates and describe circumstances of exertional heat illness. Exertional heat illness occurred at a rate of 1.20 per 100,000 athlete exposures (95% CI=1.12, 1.28). Exertional heat illnesses were widely distributed geographically, and most occurred in August (60.3%). Of the exertional heat illnesses reported during practice, almost one third (32.0%) occurred more than 2 hours into the practice session. The exertional heat illness rate in football (4.42 per 100,000 athlete exposures) was 11.4 times that in all other sports combined (95% CI=8.3, 15.5, p<0.001). In addition, approximately one third (33.6%) of exertional heat illnesses occurred when a medical professional was not onsite at the time of onset. Although most exertional heat illnesses occurred in football, athletes in all sports and all geographic areas are at risk. Because exertional heat illness frequently occurs when medical professionals are not present, it is imperative that high school athletes, coaches, administrators, and parents are trained to identify and respond to it. Implementing effective preventive measures depends on increasing awareness of exertional heat illness and relevant preventive and therapeutic countermeasures.
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Exertional heat illness can affect athletes during high-intensity or longduration exercise and result in withdrawal from activity or collapse during or soon after activity. These maladies include exercise associated muscle cramping, heat exhaustion, or exertional heatstroke. While certain individuals are more prone to collapse from exhaustion in the heat (i.e., not acclimatized, using certain medications, dehydrated, or recently ill), exertional heatstroke (EHS) can affect seemingly healthy athletes even when the environment is relatively cool. EHS is defined as a rectal temperature greater than 40-C accompanied by symptoms or signs of organ system failure, most frequently central nervous system dysfunction. Early recognition and rapid cooling can reduce both the morbidity and mortality associated with EHS. The clinical changes associated with EHS can be subtle and easy to miss if coaches, medical personnel, and athletes do not maintain a high level of awareness and monitor at-risk athletes closely. Fatigue and exhaustion during exercise occur more rapidly as heat stress increases and are the most common causes of withdrawal from activity in hot conditions. When athletes collapse from exhaustion in hot conditions, the term heat exhaustion is often applied. In some cases, rectal temperature is the only discernable difference between severe heat exhaustion and EHS in on-site evaluations. Heat exhaustion will generally resolve with symptomatic care and oral fluid support. Exercise associated muscle cramping can occur with exhaustive work in any temperature range, but appears to be more prevalent in hot and humid conditions. Muscle cramping usually responds to rest and replacement of fluid and salt (sodium). Prevention strategies are essential to reducing the incidence of EHS, heat exhaustion, and exercise associated muscle cramping.
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Exertional heat-related injuries are a risk to all physically active individuals in warm or hot environments. Unlike classic heat-related injury, exertional heat-related injuries do not require extreme ambient temperatures to cause injury. Still, exertional heat-related injuries, including heat cramps, heat syncope, heat exhaustion, heat stress, and heat stroke, can result in injuries causing a range of outcomes from minimal discomfort to death. The purpose of this paper was to describe the epidemiology of exertional heat-related injuries treated in U.S. emergency departments. A retrospective analysis was conducted using data from the National Electronic Injury Surveillance System of the U.S. Consumer Product Safety Commission for all ages from 1997 through 2006. Data provided by the National Electronic Injury Surveillance System were used to calculate national estimates of exertional heat-related injuries. Trends of exertional heat-related injuries over time were analyzed using linear regression. Nationally, an estimated 54,983 (95% CI=39995, 69970) patients were treated in U.S. emergency departments for exertional heat-related injuries from 1997 to 2006. The number of exertional heat-related injuries increased significantly from 3192 in 1997 to 7452 in 2006 (p=0.002), representing a 133.5% increase. The overall exertional heat-related injury rate per 100,000 U.S. population more than doubled from 1.2 in 1997 to 2.5 in 2006 (p=0.005). Patients aged ≤19 years accounted for the largest proportion of exertional heat-related injuries (47.6%). The majority of exertional heat-related injuries were associated with performing a sport or exercising (75.5%) and yard work (11.0%). The majority of patients (90.4%) were treated and released from the emergency department. Patients aged ≤19 years sustained a larger proportion of sports and recreation exertional heat-related injuries, whereas patients aged 40-59 years and ≥60 years sustained a larger proportion of exertional heat-related injuries from yard work. This study confirms that although there is a risk of exertional heat-related injury among all physically active individuals, sports pose a specific risk for people of all ages especially among children and adolescents playing football. Many "everyday" activities such as yard work and home maintenance also pose risks of exertional heat-related injury, particularly to those aged ≥40 years. Further research on risk factors of exertional heat-related injuries during home maintenance and yard work as well as appropriate prevention practices i