Exertional Heat Illness Research Articles

Football Practices in Hot Environments Impact Subsequent Days' Hydration.

Ashley, CD, Lopez, RM, and Tritsch, AJ. Football practices in hot environments impact subsequent days' hydration. J Strength Cond Res XX(X): 000-000, 2023-The impact of proper hydration to prevent exertional heat illness in American football has not been evaluated during high school preseason football practices in a hot environment (wet-bulb globe temperature = 31.3 ± 1.8° C). The purposes of this study were to examine the accuracy of urinary hydration measures to assess body mass (BM) changes and to examine carryover effects of consecutive practices by comparing postpractice with the next prepractice values. Before and after each of 7 outdoor practices, 31 male high school football players (age = 16 ± 1 years, height = 181.2 ± 12.0 cm, BM = 85.7 ± 19.1 kg, body mass index = 20.8 ± 1.8) provided a urine sample and were weighed to assess hydration. Sensitivity and specificity of urine color (Ucol) and urine-specific gravity (USG) to determine BM changes were determined using receiver operating characteristic (ROC) analysis. Paired samples t-tests assessed carryover effects between practices. Repeated-measures analysis of variance assessed carryover effects across practices. Significance was set at p < 0.05. Sensitivity and specificity for using Ucol or USG to determine BM changes was not significant. For Ucol, there was a carryover effect from practice numbers 2 to 3, 6 to 7 am, 7 am to 7 pm (p < 0.001 for all), and 10 to 11 (p = 0.004); most with less than 24 hours between practices. The %BM loss (%BML) was significantly greater (p = 0.001 to 0.024) after 2-a-day practices. Effects of previous days' exercise in the heat, as evidenced by higher Ucol and %BL, are greater after 2-a-day practices, which occurred on later practice days. Athletes must replenish fluids during and between practices to remain euhydrated.

Association Between Hydration Status And Incidence Of Exertional Heat Illness In A Military Cohort

Association Between Hydration Status And Incidence Of Exertional Heat Illness In A Military Cohort

Test–Retest Reliability and Minimum Detectable Change of the Athletic Trainers’ Self-Confidence Scale

The Athletic Trainers’ Self-Confidence Scale (ATSCS) is a nine-item Likert-scale questionnaire assessing the respondent’s level of agreement with statements regarding confidence in recognizing and managing exertional heat illnesses. Test–retest reliability of this instrument has not yet been established. The purpose of this study was to investigate the internal consistency, test–retest reliability, and minimum detectable change score for the composite score of the ATSCS. A total of 18 professional master of science in athletic training students (nine first-year and nine second-year students) completed the ATSCS at three testing sessions with 48 hr between sessions. The nine items of the ATSCS demonstrated good internal consistency (α = .86; 95% confidence interval [.78, .94]). The composite scores of the ATSCS demonstrated moderate test–retest reliability (intraclass correlation coefficient = .75; 95% confidence interval [.497, .893]). The calculated minimal detectable change for the composite change score was 6.19. The ATSCS has good internal reliability as well as test–retest reliability. These results display that the tool will provide consistent, reliable results of changes in athletic training students’ self-confidence.

Heat-related Physical Activity Loss Estimation And Sport Guidelines For Exertional Heat Illness Prevention In China

Heat-related Physical Activity Loss Estimation And Sport Guidelines For Exertional Heat Illness Prevention In China

Planning for heat: Time activity patterns, heat hazards, and exertional heat illnesses among American interscholastic football players

Planning for heat: Time activity patterns, heat hazards, and exertional heat illnesses among American interscholastic football players

Multiparametric cardiac magnetic resonance reveals persistent myocardial inflammation in patients with exertional heat illness.

To explore the clinical potential of multiparametric cardiac magnetic resonance (CMR) in evaluating myocardial inflammation in patients with exertional heat illness (EHI). This prospective study enrolled 28 males with EHI (18 patients with exertional heat exhaustion (EHE) and 10 with exertional heat stroke (EHS)) and 18 age-matched male healthy controls (HC). All subjects underwent multiparametric CMR, and 9 patients had follow-up CMR measurements 3months after recovery from EHI. CMR-derived left ventricular geometry, function, strain, native T1, extracellular volume (ECV), T2, T2*, and late gadolinium enhancement (LGE) were obtained and compared among different groups. Compared with HC, EHI patients showed increased global ECV, T2, and T2* values (22.6% ± 4.1 vs. 19.7% ± 1.7; 46.8ms ± 3.4 vs. 45.1ms ± 1.2; 25.5ms ± 2.2 vs. 23.8ms ± 1.7; all p < 0.05). Subgroup analysis showed that ECV was higher in the EHS patients than those in EHE and HC groups (24.7% ± 4.9 vs. 21.4% ± 3.2, 24.7% ± 4.9 vs. 19.7% ± 1.7; both p < 0.05). Repeated CMR measurements at 3months after baseline CMR showed persistently higher ECV than HC (p = 0.042). With multiparametric CMR, EHI patients demonstrated increased global ECV, T2, and persistent myocardial inflammation at 3-month follow-up after EHI episode. Therefore, multiparametric CMR might be an effective method in evaluating myocardial inflammation in patients with EHI. This study showed persistent myocardial inflammation after an exertional heat illness (EHI) episode demonstrated by multiparametric CMR, which is a potential promising method to evaluate the severity of myocardial inflammation and guide return to work, play, or duty in EHI patients. • EHI patients showed an increased global extracellular volume (ECV), late gadolinium enhancement, and T2 value, indicating myocardial edema and fibrosis. • ECV was higher in the exertional heat stroke patients than exertional heat exhaustion and healthy control groups (24.7% ± 4.9 vs. 21.4% ± 3.2, 24.7% ± 4.9 vs. 19.7% ± 1.7; both p < 0.05). • EHI patients showed persistent myocardial inflammation with higher ECV than healthy controls 3months after index CMR (22.3% ± 2.4 vs. 19.7% ± 1.7, p = 0.042).

ACSM Expert Consensus Statement on Exertional Heat Illness: Recognition, Management, and Return to Activity.

Exertional heat stroke 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 exertional heat stroke. Identifying the athlete with suspected exertional heat stroke 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 exertional heat stroke 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.

Incidence and factor analysis for the heat-related illness on the Tokyo 2020 Olympic and Paralympic Games

IntroductionAmong the 43 venues of Tokyo 2020 Olympic Games (OG) and 33 venues of Paralympic Games (PG) were held, the heat island effect was highly expected to cause heat-related illnesses...

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.

Image Improved Intravoxel Incoherent Motion MRI With Optimized Trigger Delays Based on Strain Curve Analysis to Evaluate Myocardial Microvascular Dysfunction of Exertional Heat Illness.

Intravoxel incoherent motion (IVIM) MRI has not been widely used and its role in evaluating exertional heat illness (EHI)-related myocardial involvement remains unknown. To investigate the feasibility of strain curve-derived trigger delay (TD) IVIM-MRI and its role in assessing myocardial diffusion and microvascular perfusion of EHI patients. Prospective. A total of 42 male EHI patients (median age: 21 years) and 22 age- and sex-matched healthy controls (HC). A 3-T, diffusion-weighted spin-echo echo-planar-imaging sequence. IVIM-MRI was acquired by conventional TD method (group A) or strain curve-based TD method (group B) in random order. IVIM image quality was evaluated on a 3-point Likert scale (1, nondiagnostic; 2, moderate; 3, good). Technical success was defined as image quality score=3. IVIM-MRI-derived parameters (pseudo diffusion in the capillaries [D*], perfusion fraction [f], and slow apparent diffusion coefficient [D]) were compared between EHI and HC. Student's t-tests, chi-square tests, one-way analysis of variance, receiver operating characteristic (ROC) curve analysis, Pearson's correlation coefficient (r). The statistical significance level was set at P < 0.05. IVIM-MRI image quality score (median [interquartile range]: 3 [2, 3] vs. 2 [1-3]) and technical success rate (61.9%[13/21] vs. 28.6%[6/21]) were significantly improved in group B. EHI patients showed significantly decreased D* (118.1 ± 23.3 × 10-3 mm2 /sec vs. 142.7 ± 42.6× 10-3 mm2 /sec) and f values (0.42 ± 0.12 vs. 0.51 ± 0.11) and significantly higher D values (3.0 ± 0.9× 10-3 mm2 /sec vs. 2.5 ± 0.6× 10-3 mm2 /sec) compared to HC. Relative to D and D*, f showed the most robust efficacy for detecting EHI-related myocardial injury with the highest area under the ROC curve (0.906: 95% confidence interval, 0.799, 0.967) and sensitivity of 88.5% and specificity of 85.6%. The strain curve-based TD method significantly improved image quality and technical success rate of IVIM-MRI, and f value may be an effective biomarker to assess myocardial microcirculation abnormalities of EHI patients. 2. Stage 3.

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.

Risk factors for, and prediction of, exertional heat illness in Thoroughbred racehorses at British racecourses

The development of exertional heat illness (EHI) is a health, welfare and performance concern for racehorses. However, there has been limited multivariable assessment of the possible risk factors for EHI in racehorses, despite such information being vital for regulators to effectively manage the condition. Consequently, this study aimed to identify the risk factors associated with the occurrence of EHI in Thoroughbred racehorses and assess the ability of the risk factor model to predict the occurrence of EHI in racehorses to assist in early identification. Runners at British racecourses recorded in the British Horseracing Authority database between 1st July 2010 and 30th April 2018 were used to model the probability that a horse would present with EHI as a function of a suite of environmental, horse level and race level factors. EHI was reported in 0.1% of runners. Race distance, wet bulb globe temperature, preceding 5-day temperature average, occurrence of a previous EHI incident, going, year and race off time were identified as risk factors for EHI. The model performed better than chance in classifying incidents with a mean area under the receiver operating characteristic curve score of 0.884 (SD = 0.02) but had a large number of false positives. The results provide vital evidence for industry on the need to provide appropriate cool down facilities, identify horses that have repeated EHI incidents for early intervention, and collect new data streams such as on course wet bulb globe temperature measurements. The results are especially relevant as the sport is operating in a changing climate and must mitigate against more extreme and longer spells of hot weather.

Exertional Heat Illness: Adoption of Policies and Influencing Contextual Factors as Reported by Athletic Administrators.

Little is known about the adoption by athletic administrators (AAs) of exertional heat illness (EHI) policies, and the corresponding facilitators and barriers of such policies within high school athletics. This study describes the adoption of comprehensive EHI policies by high school AAs and explores factors influencing EHI policy adoption. We hypothesized that <50% of AAs would report adoption of an EHI policy, and that the most common facilitator would be access to an athletic trainer (AT), whereas the most common barrier would be financial limitations. Cross-sectional. Level 4. A total of 466 AAs (82.4% male; age, 48 ± 9 years) completed a validated online survey to assess EHI prevention and treatment policy adoption (11 components), as well as facilitators and barriers to policy implementation. Access to athletic training services was ascertained by matching the participants' zip codes with the Athletic Training Locations and Services Project. Policy adoption, facilitators, and barriers data are presented as summary statistics (proportions, interquartile range (IQR)). A Welch t test evaluated the association between access to athletic training services and EHI policy adoption. Of the AAs surveyed, 77.9% (n = 363) reported adopting a written EHI policy. The median of EHI policy components adopted was 5 (IQR = 1,7), with only 5.6% (n = 26) of AAs reporting adoption of all policy components. AAs who had access to an AT (P = 0.04) were more likely to adopt a greater number of EHI-related policies, compared with those without access to an AT. An AT employed at the school was the most frequently reported facilitator (36.9%). Most AAs reported having written EHI policy components, and access to an AT resulted in a more comprehensive policy. Employment of an AT within high school athletics may serve as a vital component in facilitating the adoption of comprehensive EHI policies.

Heat Acclimation Knowledge among Recreational Runners

Heat acclimation (HA) is the foremost method of preventing exertional heat illness during exercise in hot and humid environments. However, the prevalence of HA training and its associated knowledge is not currently known in recreational running populations. The purpose of this study was to determine the knowledge of recreational runners toward HA. A survey consisting of 38 questions that required approximately 10-15 min to complete was disseminated to running clubs throughout the Southeastern United States. Questions were designed to collect data on participant demographics, yearly training habits, and HA knowledge. Recreational runners (N = 125) demonstrated a lack of knowledge toward proper HA training and its associated benefits. Participants largely received HA advice from their peers (31.2%) and reported no professional guidance in their training (79.2%). Finally, participants' beliefs toward proper HA training differed among training groups with moderate and high groups perceiving greater frequency, miles/wk, and min/wk as appropriate for HA compared to the low group (p ≤ 0.05). Due to the warmer temperatures and higher relative humidity experienced in the southeastern, southwestern, and mid-Atlantic locations of the United States and throughout certain regions of the European Union, governing bodies in sport and exercise science should develop more educational initiatives to convey the importance and advantages of HA, especially when runners are training for major marathons that are typically held in the late spring and early fall seasons.

An Overview of Exertional Heat Illness in Thoroughbred Racehorses: Pathophysiology, Diagnosis, and Treatment Rationale.

Exertional heat illness (EHI) is a complex medical disease. The thoroughbred (TB) racehorse is at considerable risk because of the intensity of its exercise activity and its high rate of metabolic heat production. The pathophysiology of EHI can combine aspects of both the heat toxicity pathway and the heat sepsis or endotoxemic pathway. Treatment regimes depend upon the detection of earliest clinical signs, rapid assessment, aggressive cooling and judicious use of ancillary medications. Ice-cold water provides the most rapid cooling, consistent with the need to lower core body temperature before tissue damage occurs. Research into EHI/HS by inducing the condition experimentally is ethically unjustifiable. Consequently, leading researchers in the human field have conceded that "most of our knowledge has been gained from anecdotal incidents, gathered from military personnel and athletes who have collapsed during or following physical activity, and that retrospective and case studies have provided important evidence regarding recognition and treatment of EHI". The authors' review into EHI shares that perspective, and the recommendations made herein are based on observations of heat-affected racehorses at the racetrack and their response, or lack of response, to treatment. From 2014 to 2018, 73 race meetings were attended, and of the 4809 individual starters, signs of EHI were recorded in 457. That observational study formed the basis for a series of articles which have been published under the title, 'EHI in Thoroughbred racehorses in eastern Australia', and forms the background for this review.

Efficacy of two intermittent cooling strategies during prolonged work-rest intervals in the heat with personal protective gear compared with a control condition.

Personal protective equipment(PPE)inhibits heat dissipation and elevates heat strain. Impairedcooling with PPE warrants investigation into practical strategies to improve work capacity and mitigate exertional heat illness. Examine physiological and subjectiveeffects of forearm immersion (FC), fan mist (MC), and passive cooling (PC) following three intermittent treadmill bouts while wearing PPE. Twelve males (27 ± 6years; 57.6 ± 6.2ml/kg/min; 78.3 ± 8.1kg; 183.1 ± 7.2cm) performed three 50-min (10min of 40%, 70%, 40%, 60%, 50% vVO2max)treadmill bouts in the heat (36°C, 30% relative humidity). Thirty minutes of cooling followed eachbout, using one of the three strategies per trial.Rectal temperature (Tcore), skin temperature (Tsk), heart rate (HR), heart rate recovery (HRR), rating of perceived exertion (RPE), thirst, thermal sensation (TS), and fatigue were obtained. Repeated-measures analysis of variance (condition x time) detected differences between interventions. Final Tcorewas similar betweentrials (P > .05). Cooling rates were largerin FC and MC vs PC following bout one (P < .05). HRR was greatest in FC following bouts two (P = .013) and three (P < .001). Tsk, fluid consumption, and sweat rate were similar between all trials (P > .05). TS and fatigue during bout three were lower in MC, despite similar Tcoreand HR. UtilizingFC and MC during intermittent workin the heat with PPE yields some thermoregulatory and cardiovascularbenefit, but military health and safety personnel should explore new and novelstrategies to mitigate risk and maximize performance under hot conditions while wearing PPE.

U.S. High School Coaches’ Knowledge, Perception, and Current Practices Regarding Exertional Heat Illness

Exertional heat illness (EHI) is a dangerous, but preventable and treatable condition that affects approximately 9,000 athletes each year in the United States. Unfortunately, less than 30% of schools in the United States have access to an athletic trainer, making coaches responsible for the safety of the athletes during practices and games. The purpose of this study was to evaluate the knowledge, perception, and procedures of high school coaches in the United States regarding heat illness recognition, prevention, and treatment. An online survey including Likert items and open-ended questions was completed by 1,676 coaches from 16 states and compared between age, coaching experience, gender, education level, experience handling EHI, state, and the completion of either a general coaching certification or a heat safety certification. Average knowledge score among coaches was 74%. Coaches with experience handling or witnessing EHI, more years of coaching experience, older age, and the completion of a coaching certification had significantly higher level of knowledge than others. Results revealed that evidence-based strategies and state mandates aimed at preventing EHI are not being implemented. More training in prevention, recognition, and treatment of EHI is necessary for all individuals involved with high school athletes to prevent avoidable deaths.

Management of a Special Warfare Trainee With Repeat Exertional Heat Stroke: A Case Study.

Exertional heat stroke (EHS) is the most deadly form the exertional heat illness with a higher incidence among active duty US military members than in the general population. Current guidelines on EHS recovery timelines and return to duty vary among the military branches. In some cases, individuals experience prolonged heat and exercise intolerance with repeat exertional heat illness events, which can complicate the recovery process. Management and rehabilitation of such individuals is unclear. This manuscript addresses the case and management of a US Air Force Special Warfare trainee who experienced 2 episodes of EHS, despite early recognition, gold standard treatment, and undergoing 4weeks of a stepwise recovery after an initial EHS. After the second episode, a 3-step process was utilized, consisting of a prolonged and personalized recovery period, heat tolerance testing using Israeli Defense Force advanced modeling, and stepwise reacclimatization. This process allowed the trainee to successfully recover from repeat EHS and return to duty, and set a framework for future repeat EHS treatment guidelines. In individuals with repeat EHS, a prolonged recovery period followed by heat tolerance testing can be used to demonstrate appropriate thermotolerance and safely clear an individual to begin stepwise reacclimatization. Overall, patient care and military readiness may be improved by unified Department of Defense guidelines for return to duty after EHS.

Hydration: Tactical and Practical Strategies.

Full-spectrum Human Performance Optimization (HPO) is essential for Special Operations Forces (SOF). Adequate hydration is essential to all aspects of performance (physical and cognitive) and recovery. Water losses occur as a result of physical activity and can increase further depending on clothing and environmental conditions. Without intentional and appropriate strategic hydration planning, Operators are at increased risk for degradation in performance and exertional heat illness. The purpose of this article is to highlight current best practices for maintaining hydration before, during, and after activity, while considering various environmental conditions. Effective leadership and planning are necessary for preparing Operators for successful military operations.

Exertional Heat Illness: A Yearly Preventable Cause of Illness and Death in Athletes

Every summer, exertional heat illness in athletes becomes the center of attention among coaches, athletic trainers, and physicians across the United States. This topic has recently received increased attention as seven football players died from exertional heat illness between July 2020 and August 2021[1] . Health professionals believe that sport-related heat illnesses can be prevented through following published sports guidelines, protocols for weather monitoring and water breaks, and using appropriate conditioning during practice sessions. This topic has become such an issue that several states and local governing bodies have enacted legislation and policy for exertional heat illness education and training for coaches, players, and parents[2,3,32] . Every year there are coaches and programs that abstain from following guidelines, disregard weather conditions, and force extreme conditioning, referred to as “irrational intensity”[4] . This blatant disregard for player safety can lead to severe cases of exertional heat illness and even death. The COVID-19 pandemic has had an impact on athletics for nearly two years. When looking at the scope of athletics this upcoming summer, it is reasonable to say that we may be heading towards a return to more typical summer activities. As COVID-19 restrictions loosen, there will likely be an increase in sports participation this summer compared to the summers of 2020 and 2021. Therefore, it is of the utmost importance that the sporting community is educated on a preventable illness that plagues athletes during hot weather seasons. Through education, accountability, enacting protocols, and following guidelines set by health professionals[5-7] , we can help prevent these needless cases of severe heat illness and death.