Risk Of Exertional Heat Illness Research Articles

Regulation of body temperature and blood pressure in women: Mechanisms and implications for heat illness risk.

Increasing global temperatures due to ongoing climate change phenomena have resulted in increased risk of exertional heat illness in otherwise healthy, young individuals who work or play in the heat. With increasing participation of women in athletic, military and industrial activities that involve exertion in the heat, there is a growing need to study female physiology in this context. Mechanisms controlling blood pressure and body temperature have substantial overlap in humans, largely due to autonomic mechanisms which contribute to both. Similarly, illnesses that result from excessive heat exposure can often be traced back to imbalances in one or more of these autonomic mechanisms. In recent years, there has been increased recognition of the importance of sex as a biological variable for basic and applied research in these areas. The goal of this paper is to present an update on the integrative physiology and pathophysiology of responses to heat stress in women (thermoregulation and blood pressure regulation). In this context, it is often the case that differences between sexes are presented as 'advantages' and 'disadvantages' of one sex over the other. In our opinion, this is an over-simplification of the physiology which ignores the nuances and complexities of the integrative physiology of responses to heat exposure and exercise, and their relevance for practical outcomes.

Wearable and ingestible technology to evaluate and prevent exertional heat illness: A narrative review.

Exertional heat illness remains a constant threat to the athlete, military service member, and laborer. Recent increases in the number and intensity of environmental heat waves places these populations at an ever increasing risk and can be deadly if not recognized and treated rapidly. For this reason, it is extremely important for medical providers to guide athletes, service members, and laborers in the implementation of awareness, education, and measures to reduce or mitigate the risk of exertional heat illness. Within the past 2 decades, a variety of wearable technology options have become commercially available to track an estimation of core temperature, yet questions continue to emerge as to its use, effectiveness, and practicality in athletics, the military, and the workforce. There is a paucity of data on the accuracy of many of these newer devices in the setting of true heat stroke physiology, and it is important to avoid overreliance on new wearable technology. Further research and improvement of this technology are critical to identify accuracy in the diagnosis and prevention of EHI.

Quantifying Exercise Heat Acclimatisation in Athletes and Military Personnel: A Systematic Review and Meta-analysis.

Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat. The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel. Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6weeks were included. MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022. A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias. A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated. Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of - 0.19°C [90% CrI: - 0.41 to 0.05, Pd = 91%] and - 6beats·min-1 [90% CrI: - 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by - 0.24°C [90% CrI: - 0.67 to 0.20, Pd = 85%] and - 7beats·min-1 [90% CrI: - 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01L·h-1 [90% CrI: - 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation. Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length. CRD42022337761.

Variations of wet-bulb globe temperature across high school athletics in South Carolina.

The purpose was to describe wet bulb globe temperature (WBGT) throughout a high school fall athletic season (August to November) after a state-wide mandate requiring schools to use a WBGT-guided activity modification table with categories (AMTC). A cross-sectional research design utilized 30 South Carolina high schools. The independent variables were region (upstate, midlands, and coastal), sport (football, tennis, cross-country), month, start times (7-10 am, 10 am-3pm, 3-6pm, and 6-9pm), and event type (practice, competition). Dependent variables were event frequency, average WBGT, and AMTC. Practice WBGT was 78.7 ± 8.2 °F (range: 34.7 to 99.0 °F). A significant difference for WBGT across month (F6, 904.7 = 385.07, P < 0.001) existed, with early September hotter than all other months (84.8 °F ± 3.8, P < 0.001). Every month had practices in each AMTC, until early November. Most events (64.6%, n = 1986) did not change AMTC; however, 9.1% (n = 281) changed to a hotter category. The 10 am-3pm start time was significantly hotter than all other time frames (83.0 °F ± 7.2, P < 0.05). Tennis experienced hotter practices (79.9 °F ± 6.9) than football (78.4 °F ± 8.5; P < 0.001) and cross country (78.2 °F ± 8.8, P < 0.001). Schools in the Midlands experienced hotter practices (80.1 °F ± 7.8) than upstate (P < 0.001) and coastal schools (P = 0.005). Competition WBGT was significantly cooler than practices (72.3 ± 10.5 °F, t = 12.04, P < 0.001) and differed across sports (F2, 20.78 = 18.39, P < .001). Both cross-country (P = 0.003) and tennis (P < 0.001) were hotter than football. Schools should continuously monitor WBGT throughout practices and until November to optimize AMTC use. Risk mitigation strategies are needed for sports other than football to decrease the risk of exertional heat illnesses.

Effect of high ambient temperature on physiological responses during incremental exercise in Thoroughbred horses

Several reports have suggested that the risk of exertional heat illness (EHI) in Thoroughbred racehorses increases in high ambient temperatures. Heat dissipation in horses during exercise becomes less efficient when the body temperature and ambient temperature are close. Therefore, we hypothesised that exercise at 40 °C may increase body temperature, oxygen consumption, and cardiac output during incremental exercise tests compared to 20 and 30 °C. Six trained Thoroughbred horses were studied in a randomised, crossover design at three ambient temperatures with a 6-day washout period. Using a 3% inclined treadmill, horses performed incremental exercise tests at 1.7, 3.5, 6, 8, and 10 m/s for 90 s at ambient temperatures of 20, 30, and 40 °C. The effects of ambient temperature at 10 m/s on physiological variables were analysed using mixed models (P&lt;0.05). Pulmonary arterial temperature and rectal temperature at 40 °C were higher than those at 20 °C (P&lt;0.001) and 30 °C (P&lt;0.001). Similarly, oxygen consumption (vs 20 °C, P=0.009; vs 30 °C, P=0.006) and cardiac output (vs 20 °C, P=0.001; vs 30 °C, P=0.001) at 40 °C were higher than those at 20 and 30 °C. Arterial O2 partial pressure, O2 saturation, and pH at 40 °C were lower than those at 20 and 30 °C. Arterial CO2 partial pressure at 40 °C was higher than that at 20 and 30 °C. No differences were observed in arterial-mixed venous O2 concentration difference (P=0.391) and plasma lactate concentration (P=0.134) at different ambient temperatures. These results indicate that exercise at 40 °C causes excessive high body temperature, decreased running economy, and increased cardiac output compared to exercise at 20 and 30 °C. We strongly suggest that trainers and veterinarians should anticipate the occurrence of increased thermal stresses when ambient temperature is extremely high even in dry conditions and prepare to mitigate the risk of EHI from the perspective of equine welfare.

Prospective Validation of 2B-Cool : Integrating Wearables and Individualized Predictive Analytics to Reduce Heat Injuries.

An uncontrollably rising core body temperature (T C ) is an indicator of an impending exertional heat illness. However, measuring T C invasively in field settings is challenging. By contrast, wearable sensors combined with machine-learning algorithms can continuously monitor T C nonintrusively. Here, we prospectively validated 2B-Cool , a hardware/software system that automatically learns how individuals respond to heat stress and provides individualized estimates of T C , 20-min ahead predictions, and early warning of a rising T C . We performed a crossover heat stress study in an environmental chamber, involving 11 men and 11 women (mean ± SD age = 20 ± 2 yr) who performed three bouts of varying physical activities on a treadmill over a 7.5-h trial, each under four different clothing and environmental conditions. Subjects wore the 2B-Cool system, consisting of a smartwatch, which collected vital signs, and a paired smartphone, which housed machine-learning algorithms and used the vital sign data to make individualized real-time forecasts. Subjects also wore a chest strap heart rate sensor and a rectal probe for comparison purposes. We observed very good agreement between the 2B-Cool forecasts and the measured T C , with a mean bias of 0.16°C for T C estimates and nearly 75% of measurements falling within the 95% prediction intervals of ±0.62°C for the 20-min predictions. The early-warning system results for a 38.50°C threshold yielded a 98% sensitivity, an 81% specificity, a prediction horizon of 35 min, and a false alarm rate of 0.12 events per hour. We observed no sex differences in the measured or predicted peak T C . 2B-Cool provides early warning of a rising T C with a sufficient lead time to enable clinical interventions and to help reduce the risk of exertional heat illness.

Heat preparedness and exertional heat illness in Paralympic athletes: A Tokyo 2020 survey

ABSTRACT Paralympic athletes may be at increased risk for exertional heat illness (EHI) due to reduced thermoregulatory ability as a consequence of their impairment. This study investigated the occurrence of heat-stress related symptoms and EHI, and the use of heat mitigation strategies in Paralympic athletes, both in relation to the Tokyo 2020 Paralympic Games and previous events. Paralympic athletes competing in Tokyo 2020 were invited to complete an online survey five weeks prior to the Paralympics and up to eight weeks after the Games. 107 athletes (30 [24–38] years, 52% female, 20 nationalities, 21 sports) completed the survey. 57% of respondents had previously experienced heat-stress related symptoms, while 9% had been medically diagnosed with EHI. In Tokyo, 21% experienced at least one heat-stress related symptom, while none reported an EHI. The most common symptom and EHI were, respectively, dizziness and dehydration. In preparation for Tokyo, 58% of respondents used a heat acclimation strategy, most commonly heat acclimatization, which was more than in preparation for previous events (45%; P = 0.007). Cooling strategies were used by 77% of athletes in Tokyo, compared to 66% during past events (P = 0.18). Cold towels and packs were used most commonly. Respondents reported no medically-diagnosed EHIs during the Tokyo 2020 Paralympic Games, despite the hot and humid conditions in the first seven days of competition. Heat acclimation and cooling strategies were used by the majority of athletes, with heat acclimation being adopted more often than for previous competitions.

Dynamic Relationship Between Heart Rate And Core Temperature During Exercise-heat Stress And Iced Sheet Cooling

Athletes, military personnel, and others who perform physical work in the heat are at risk for exertional heat illness due to the combined presence of high ambient temperature and elevated metabolic heat production. Cooling with iced sheets is an immediate treatment used by the military and others to rapidly decrease body temperature in a field setting. Physiologically, increases in core temperature (Tc) and heart rate (HR) contribute to the cardiovascular strain associated with exercising in the heat. This increased HR is linked to the combination of metabolic (exercise) and thermal (environmental) requirements for systemic blood flow (i.e. cardiac output). Mechanisms include both autonomic neural and local influences of temperature on the heart. PURPOSE: To quantify the dynamic response of HR to changes in Tc during exercise in the heat and subsequent iced sheet cooling. We hypothesized that for a given Tc, HR would be higher during increases in Tc compared to during decreases in Tc. METHODS: Nine healthy (n = 8 males) volunteers (age 25 ± 6 y, ht 176.9 ± 9.7 cm, wt 86.6 ± 15.9 kg, body surface area 2.03 ± 0.2 m2) participated in a exercise-heat stress protocol consisting of up to 180 minutes of treadmill walking (3.5 mi·hr-1, 5% grade, in 40 °C, 30% RH). Volunteers then lay supine and underwent iced-sheet cooling (ISC) (bed sheets placed in 5-gallon ice buckets with 2/3 ice, 1/3 cool water; rotated out with pre-soaked sheets every 3 min) until Tc decreased to ≤38.0 °C. Individual changes in HR during both exercise and cooling were compared at Tc = 38.2 and 38.6 °C using 2-way analysis of variance. RESULTS: HR was significantly higher for a given Tc when Tc was increasing during exercise compared to when it was decreasing during cooling. For example, during exercise, HR was 150 ± 13 bpm at Tc = 38.2 °C and 157 ± 9 bpm at Tc = 38.6 °C, while during cooling, HR was 96 ± 10 bpm at Tc = 38.2 °C and 104 ± 14 bpm at Tc = 38.6 °C (both p < 0.01). CONCLUSION: These data confirm the efficacy of iced-sheet cooling for decreasing cardiovascular strain associated with heat-related events. The fact that cooling resulted in lower HR for a given Tc suggests that exercise associated autonomic reflexes predominated over direct effects of temperature on sinus node control of HR. Supported by USAMRDC; author views not official US Army or DoD policy.

Increased risk of heat stress conditions during the 2022 Comrades Marathon

The Comrades Marathon is South Africa’s – and the world’s – most recognised and largest ultra-marathon event, with over 15 000 participants from across the globe competing in the 89-km road running event each year. Historically, the event has been held before the start of austral winter (20 May – 17 June). However, in 2022, organisers of the race moved the event to 28 August, when austral spring commences. We explore the climate, in particular the Universal Thermal Comfort Index (UTCI), of past Comrades events (1980-2019) and compare these data to UTCI data of the new proposed date (28 August) for the same period. The climatology for May, June, July and August was determined to identify periods with the lowest risk for ‘strong’ to ‘very strong’ heat stress. Results show that participants’ risk of exposure to ‘strong’ heat stress and ‘very strong’ heat stress periods will be more likely if the event is held in August as compared to the original event dates. Therefore, it is concluded that mid-June to mid-July has the lowest risk of heat stress exposure along the route. Runners and organisers should be aware of the higher risk of exertional heat illness during the 2022 Comrades Marathon to ensure safe participation. Significance: The new proposed date for the Comrades Marathon will increase the risk of exposure to ‘strong’ and ‘very strong’ heat stress conditions, as defined by the Universal Thermal Comfort Index (UTCI). The UTCI indicates that mid-June to mid-July has the lowest risk of heat stress exposure at the three reference points along the route. Organisers should warn runners of the higher risk of exertional heat illness due to the possible exposure to high UTCI values or more unfavourable climatological conditions. Furthermore, runners should be informed of a variety of preventative strategies to ensure safe participation.

Factors Affecting Incidence Rate of Exertional Heat Illnesses: Analysis of 6 Years of High School Football Practices in North Central Florida

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.

An investigation into environmental variables influencing post-race exertional heat illness in thoroughbred racehorses in temperate eastern Australia.

Exertional heat illness (EHI) is a syndrome that occurs when metabolic heat production from muscular contraction exceeds the rate at which it can be dissipated. Core body temperature rises to critical levels, causing hyperthermia and central nervous system dysfunction. Best practice for the prevention of EHI centres around early detection, rapid response and aggressive cooling. Advance planning enables risk mitigation measures. The more that is known about EHI in horses, the better prepared those in the positions of responsibility can be to anticipate events in which the risk of EHI may be elevated. This prospective, observational study investigated environmental risk factors associated with the occurrence of EHI. From 2014 to 2018, the number of horses exhibiting the symptoms of post-race EHI was recorded at 73 convenience sampled race meetings. Of the 4809 starters, the signs of EHI were recorded for 457. Thermal environmental data were measured and included ambient temperature, radiant heat, vapor pressure (humidity) and wind speed (WS). Mixed linear regression models were computed to assess the associations between the occurrence and incidence of post-race EHI and the four thermal environmental variables. The analysis showed that vapor pressure and WS had the largest effects on the occurrence of post-race EHI. The major limitations were that the race meetings selected were convenience sampled according to attendance by the first author and individual horse data were not available. EHI is influenced by a complex interaction of independently acting environmental variables, but warm, windless, humid days are most likely to result in the cases of EHI.

Thermoregulatory Responses with Size-matched Simulated Torso or Limb Skin Grafts.

This study aimed to test the hypothesis that a simulated burn injury on the torso will be no more or less detrimental to core temperature control than on the limbs during uncompensable exercise-heat stress. Nine nonburned individuals (7 men, 2 women) completed the protocol. On separate occasions, burn injuries of identical surface area (0.45 ± 0.08 m2 or 24.4% ± 4.4% of total body surface area) were simulated on the torso or the arms/legs using an absorbent, vapor-impermeable material that impedes sweat evaporation in those regions. Participants performed 60 min of treadmill walking at 5.3 km·h-1 and a 4.1% ± 0.8% grade, targeting 6 W·kg-1 of metabolic heat production in 40.1°C ± 0.2°C and 19.6% ± 0.6% relative humidity conditions. Rectal temperature, heart rate, and perceptual responses were measured. Rectal temperature increased to a similar extent with simulated injuries on the torso and limbs (condition-by-time interaction, P = 0.86), with a final rectal temperature 0.9°C ± 0.3°C above baseline in both conditions. No differences in heart rate, perceived exertion, or thermal sensation were observed between conditions (condition-by-time interactions, P ≥ 0.50). During uncompensable exercise-heat stress, sized-matched simulated burn injuries on the torso or limbs evoke comparable core temperature, heart rate, and perceptual responses, suggesting that the risk of exertional heat illness in such environmental conditions is independent of injury location.

Heat Stress Management in the Military: Wet-Bulb Globe Temperature Offsets for Modern Body Armor Systems.

The aim of this study was to model the effect of body armor coverage on body core temperature elevation and wet-bulb globe temperature (WBGT) offset. Heat stress is a critical factor influencing the health and safety of military populations. Work duration limits can be imposed to mitigate the risk of exertional heat illness and are derived based on the environmental conditions (WBGT). Traditionally a 3°C offset to WBGT is recommended when wearing body armor; however, modern body armor systems provide a range of coverage options, which may influence thermal strain imposed on the wearer. The biophysical properties of four military clothing ensembles of increasing ballistic protection coverage were measured on a heated sweating manikin in accordance with standard international criteria. Body core temperature elevation during light, moderate, and heavy work was modeled in environmental conditions from 16°C to 34°C WBGT using the heat strain decision aid. Increasing ballistic protection resulted in shorter work durations to reach a critical core temperature limit of 38.5°C. Environmental conditions, armor coverage, and work intensity had a significant influence on WBGT offset. Contrary to the traditional recommendation, the required WBGT offset was &gt;3°C in temperate conditions (&lt;27°C WBGT), particularly for moderate and heavy work. In contrast, a lower WBGT offset could be applied during light work and moderate work in low levels of coverage. Correct WBGT offsets are important for enabling adequate risk management strategies for mitigating risks of exertional heat illness.

Seasonal Trends for Environmental Illness Incidence in the U.S. Army.

The incidence of and risk factors for exertional heat illness (EHI) and cold weather injury (CWI) in the U.S. Army have been well documented. The "heat season", when the risk of EHI is highest and application of risk mitigation procedures is mandatory, has been arbitrarily defined as May 1 through September 30, while the "cold season" is understood to occur from October 1 to April 30 each year. The proportions of EHI and CWI that occur outside of the traditional heat and cold seasons are unknown. Additionally, it is unknown if either of the seasonal definitions are appropriate. The primary purpose of this study was to determine the proportion of EHI and of CWI that occur within the commonly accepted seasonal definitions. We also report the location-specific variability, seasonal definitions, and the demographic characteristics of the populations. The U.S. Army installations with the highest frequency of EHI and of CWI from 2008 to 2013 were identified and used for analysis. In total there were 15 installations included in the study, with five installations used for analysis in both the EHI and CWI projects. In- and out-patient EHI and CWI data (ICD-9-CM codes 992.0 to 992.9 and ICD codes 991.0 to 991.9, respectively) were obtained from the Defense Medical Surveillance System. Installation-specific denominator data were obtained from the Defense Manpower Data Center, and incidence rates were calculated by week, for each installation. Segmental (piecewise) regression analysis was used to determine the start and end of the heat and cold seasons. Our analysis indicates that the heat season starts around April 22 and ends around September 9. The cold season starts on October 3 and ends on March 24. The majority (n = 6,445, 82.3%) of EHIs were diagnosed during the "heat season" of May 1 to September 30, while 10.3% occurred before the heat season started (January1 to April 30) and 7.3% occurred after the heat season ended (October 1 to December 31). Similar to EHI, 90.5% of all CWIs occurred within the traditionally defined cold season, while 5.7% occurred before and 3.8% occurred after the cold season. The locations with the greatest EHI frequency were Ft Bragg (n = 2,129), Ft Benning (n = 1,560), and Ft Jackson (n = 1,538). The bases with the largest proportion of CWI in this sample were Ft Bragg (17.8%), Ft Wainwright (17.2%), and Ft Jackson (12.7%). There were considerable inter-installation differences for the start and end dates of the respective seasons. The present study indicates that the traditional heat season definition should be revised to begin ∼3 weeks earlier than the current date of May 1; our data indicate that the current cold season definition is appropriate. Inter-installation variability in the start of the cold season was much larger than that for the heat season. Exertional heat illnesses are a year-round problem, with ∼17% of all cases occurring during non-summer months, when environmental heat strain and vigilance are lower. This suggests that EHI mitigation policies and procedures require greater year-round emphasis, particularly at certain locations.

Core Body Temperatures in Collegiate Marching Band Artists During Rehearsals and Performances.

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. To examine core temperature (Tc) and EHI risk factors in MB artists. Descriptive epidemiology study. Three rehearsals and 2 football games for 2 National Collegiate Athletic Association Division I institution's MBs. 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. 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. 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. Marching band artists experienced high Tc during activity and should have access to athletic trainers who can implement EHI-prevention and -management strategies.

Perceptual strain in a compensable hot environment: Accuracy and clinical correlates.

Heat strain monitoring indexes are important to prevent exertional heat illness (EHI) and uncover risk factors. Two indexes are the Physiological Strain Index (PSI) and a subjective PSI analogue, the Perceptual Strain Index (PeSI). The PeSI is a feasible alternative to PSI in field conditions, although the validity has been variable in previous research. However, the PeSI has been rarely examined at a low heat strain with compensable heat stress, such as during a heat tolerance test (HTT). This study evaluated the discrepancy between the maximal PeSI and maximal PSI achieved during a HTT and determined their association with EHI risk factors, including history of EHI, percent body fat (%BF), relative VO2max, fatigue and sleep status (n = 121; 47 without prior EHI, 74 with prior EHI). The PSI was calculated using the change in rectal temperature (Tre) and heart rate (HR) and PeSI was calculated based on the formula containing thermal sensation (TS), a Tre analogue, and rate of perceived exertion (RPE), a HR analogue. Significant associations were identified between PSI and PeSI and between PSIHR and PeSIHR in the total sample and between PSI and PeSI in the EHI group. Bland-Altman analyses indicated PeSI underestimated PSI in the total sample, PSIHR was greater than PeSIHR, and that PSIcore and PeSIcore were not significantly different, but values varied widely at different heat strains. This indicates the use of RPE underestimates HR and that the accuracy of TS to predict Tre may be subpar. This study also demonstrated that participants with higher %BF have a decreased perception of heat strain and that post-fatigue, sleep status and a prior EHI may increase the perception of heat strain. Overall, these results suggest that PeSI is a poor surrogate for PSI in a compensable heat stress environment at low heat strain.

Collegiate Marching Band Artists Experience High Core Body Temperatures during Rehearsals and Performances.

No research has investigated thermoregulatory responses and exertional heat illness (EHI) risk factors in marching band (MB) artists performing physical activity in high environmental temperatures. Examine core temperature (Tc) and EHI risk factors in MB artists. Descriptive epidemiology study. Three rehearsals and 2 football games for 2 NCAA Division I MBs. Nineteen volunteers completed the study (female = 13, males = 6; age = 20.5 ± 0.9 years; weight = 75.0 ± 19.1 kg; height = 165.1 ± 7.1 cm). We measured Tc pre-, post-, and every 15 minutes during activity and recorded wet-bulb globe temperature (WBGT) and relative humidity (RH) every 15 minutes. Other variables included activity time and intensity, ground surface, hydration characteristics (fluid volume, sweat rate, urine specific gravity, percent body mass loss [%BM]), and medical history (eg, previous EHI, medications). Statistical analysis included descriptives (mean ± standard deviation), comparative analyses determined differences within and between days, and linear regression identified variables that significantly explained Tc. Mean rehearsal time = 102.8 ± 19.8 minutes and game time = 260.5 ± 47.7 minutes. Max game Tc (39.1 ± 1.1°C) was significantly higher than rehearsal (38.4 ± 0.7°C, P = .003). The highest max game Tc = 41.2°C. Participants consumed significantly more fluid than their sweat rates (P < .003), which minimized %BM loss, particularly during rehearsals (-0.4 ± 0.6%). Mean game %BM loss = -0.9 ± 2.0%; however, 63.6% of the time, participants reported hypohydrated to game day. Max Tc was significantly predicted by max WBGT, max RH, ground surface, using mental health medications, and hours of sleep (adjusted R2 = 0.542, P < .001). Marching band artists experience high Tc during activity and should have access to athletic trainers who can implement EHI prevention and management strategies.

The Appropriation of Product Design as Solution to Minimise Risk of Exertional Heat Illness among Marathon Runners

The intensity of environmental heat stress during a marathon race increases the runner's metabolic heat production. Based on series of participatory studies and interview sessions with 100 respondents among runners, the contributing factors to this homeostatic imbalance risk are the excessive amount of body-water deficit from extensive sweating, and the rapid increase of cardiovascular and thermal strain while running. In addition, environmental factors such as humidity, the increase of air temperature, wind speed and solar radiation contribute to the marathon runner's low performance during running with the paucity of cooling strategy that results in the increase of core body temperature with symptoms of exertional heat illness. This paper elucidates the integration of the statistical and theoretical studies of exertional heat illness and the human physiological responses complementing with the product design context. The integration demonstrates the synchronisation of design thinking process within the ergonomics ergosystem framework to develop the appropriate prototype design for marathon runners. As outcome, this research has successfully developed a running suit as its design proposal to minimise exertional heat illness risk and promote the runner's safety, wellbeing and performance in the heat.

Barriers and Facilitators Faced by Athletic Trainers Implementing National Athletic Trainers' Association Inter-Association Task Force Preseason Heat-Acclimatization Guidelines in US High School Football Players.

The aim of the National Athletic Trainers' Association Inter-Association Task Force (NATA-IATF) preseason heat-acclimatization guidelines was to acclimatize high school athletes to the environment during the first 2 weeks of the preseason and reduce the risk of exertional heat illness. To identify barriers and facilitators that high school athletic trainers (ATs) encountered when implementing the NATA-IATF guidelines. Qualitative study. Individual phone interviews with all participants. Thirty-three ATs (16 men, 17 women; age = 36.0 ± 12.0 years, athletic training experience = 12.9 ± 10.5 years) representing 19 states (4 with state mandates) were interviewed before data saturation was achieved. Participants were purposefully sampled from a larger investigation based on stratification of US Census region and preidentified high school compliance with the NATA-IATF guidelines. A cross-sectional, semistructured phone interview (6 steps) was conducted with each participant and then transcribed verbatim. A 7-person research team (5 coders, 2 auditors) coded the data into themes and categories, focusing on consensus of data placement to reduce bias and ensure accuracy. Facilitators and barriers that influenced successful guideline implementation were (1) perceived stakeholder access, (2) perceived stakeholder role, (3) capability and capacity, (4) school culture, (5) logistical support, (6) resources, (7) physical environment, and (8) consistency of the guidelines. Overall, participants discussed facilitators and barriers within each category based on their experiences and circumstances. Athletic trainers faced numerous concerns regarding compliance with the NATA-IATF preseason heat-acclimatization guidelines. Multiple levels of influence should be targeted to improve implementation. These include intrapersonal factors by giving ATs the education and self-efficacy to support advocacy for implementation, interpersonal components by establishing strong collaborative networks for change, community and environmental factors by optimizing school culture and community resources for implementation, and policy aspects by establishing consistent guidelines across all bodies.

Exertional Heat Illness Preparedness Strategies: Environmental Monitoring Policies in United States High Schools.

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.