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INTRODUCTION: The recommended treatment for exertional heat stroke is immediate, whole-body immersion in < 10 °C water until rectal temperature (Tre) reaches ≤ 38.6 °C. However, real-time Tre assessment is not always feasible or available in field settings or emergency situations. We defined and validated immersion durations for water temperatures of 2-26 °C for treating exertional heat stroke. METHODS: We compiled data for 54 men and 18 women from 7 previous laboratory studies and derived immersion durations for reaching 38.6 °C Tre. The resulting immersion durations were validated against the durations of cold-water immersion used to treat 162 (98 men; 64 women) exertional heat stroke cases at the Falmouth Road Race between 1984 and 2011. RESULTS: Age, height, weight, body surface area, body fat, fat mass, lean body mass, and peak oxygen uptake were weakly associated with the cooling time to a safe Tre of 38.6 °C during immersions to 2-26 °C water (R2 range: 0.00-0.16). Using a specificity criterion of 0.9, receiver operating characteristics curve analysis showed that exertional heat stroke patients must be immersed for 11-12 min when water temperature is ≤ 9 °C, and for 18-19 min when water temperature is 10-26 °C (Cohen's Kappa: 0.32-0.75, p < 0.001; diagnostic odds ratio: 8.63-103.27). CONCLUSION: The reported immersion durations are effective for > 90% of exertional heat stroke patients with pre-immersion Tre of 39.5-42.8 °C. When available, real-time Tre monitoring is the standard of care to accurately diagnose and treat exertional heat stroke, avoiding adverse health outcomes associated with under- or over-cooling, and for implementing cool-first transport second exertional heat stroke policies.
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Temperatura Corporal , Golpe de Calor , Masculino , Humanos , Feminino , Temperatura , Imersão , Água , Exercício Físico , Golpe de Calor/terapia , Golpe de Calor/diagnóstico , Temperatura BaixaRESUMO
BACKGROUND: Exertional heat illnesses (EHIs), specifically exertional heat stroke (EHS), are a top cause of nonaccidental death among U.S. laborers. EHS management requires coordination between Emergency Medical Services (EMS) and workplace officials to implement cold water immersion (CWI) and cool first, transport second (CFTS). OBJECTIVE: The purpose of this article was to quantify and identify existing statewide EMS guidelines, determine whether statewide EHS guidelines improved outcomes for EHIs in laborers, and examine the odds of laborer EHS fatalities when best practices are present in EMS statewide guidelines. METHODS: The Paramedic Protocol Provider database and official EMS websites were examined to determine which U.S. states had statewide EMS guidelines and, for those with statewide guidelines, a two-way χ2 analysis with associated odds ratios examined EHI outcomes. Statewide EMS guidelines underwent content analysis by three independent reviewers regarding EHS best practices. Significance was set a priori at p < 0.05. RESULTS: Among 50 states, the District of Columbia, and Puerto Rico, 57.7% (n = 30) had statewide EMS guidelines and 42.3% (n = 22) did not. There was a significant association for EHI outcome for states recommending CWI as a cooling method vs. those that did not (χ21 = 3.336; p = 0.049). The odds of EHS deaths for laborers were 3.0 times higher if CWI was not included in the EMS guidelines. There was a significant association in EHI outcomes for states without CFTS (χ21 = 5.051; p = 0.017). The odds of laborers dying from EHS were 3.7 times higher in states without CFTS. CONCLUSIONS: Laborers are 3.0 and 3.7 times less likely to die from EHS when statewide EMS guidelines include CWI and CFTS, respectively.
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Serviços Médicos de Emergência , Golpe de Calor , Humanos , Golpe de Calor/terapia , Golpe de Calor/mortalidade , Serviços Médicos de Emergência/métodos , Serviços Médicos de Emergência/normas , Serviços Médicos de Emergência/estatística & dados numéricos , Estados Unidos , Guias de Prática Clínica como Assunto , Esforço Físico , Guias como Assunto/normas , MasculinoRESUMO
ABSTRACT: Earp, JE, Stearns, RL, Agostinucci, J, Lepley, AS, and Ward-Ritacco, CL. Total body and extracellular water measures are unrelated to cramp sensitivity in euhydrated cramp-prone individuals. J Strength Cond Res 36(9): 2653-2656, 2022-Spectral bioelectrical impedance analysis (BIA) is a valid and noninvasive tool for measuring total body water (TBW), intracellular water (ICW), and extracellular water (ECW). As altered hydration and electrolyte imbalance have been proposed as one of 2 etiologies for exercise-associated muscle cramps (EAMC), the purpose of this study was to determine if distribution of body water is related to cramp sensitivity in similarly hydrated cramp-prone individuals. To this end, 11 euhydrated subjects who regularly experience EAMC had their relative TBW, ICW, and ECW assessed using 8-pole spectral BIA. Subjects' cramp sensitivity was then assessed by electrically stimulating the tibial nerve at increasing frequencies until a muscle cramp occurred, allowing for the determination of the threshold frequency (TF) at which the cramp occurred. It was observed that TF was not significantly related to TBW ( r = 0.087, p = 0.368), ICW ( r = 0.105, p = 0.338), ECW ( r = 0.087, p = 0.368), or ECW:TBW ( r = 0.147, p = 0.280). As cramp etiology is poorly understood, these results add to a growing body of literature questioning the role of hydration and electrolyte imbalance in EAMC. Although fluid distribution may be unrelated to TF in those who commonly experience EAMC, additional research is needed to compare those who commonly experience cramps (athletes as well as individuals with specific neuropathies or pharmacologically induced cramps) with those who do not experience cramps and to determine if acute shifts in body water compartmentalization are related to changes in cramp sensitivity.
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Cãibra Muscular , Água , Atletas , Composição Corporal , Água Corporal/química , Água Corporal/fisiologia , Impedância Elétrica , Humanos , Cãibra Muscular/etiologia , Água/análiseRESUMO
INTRODUCTION: Dehydration is known to impair health, quality of daily life, and exercise performance [
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Índice de Massa Corporal , Desidratação/urina , Estado de Hidratação do Organismo/fisiologia , Sede/classificação , Urinálise/classificação , Biomarcadores/urina , Peso Corporal , Cor , Feminino , Humanos , Masculino , Concentração Osmolar , Gravidade Específica , Urinálise/métodos , Equilíbrio Hidroeletrolítico , Adulto JovemRESUMO
Background and Objectives: The purpose of this systematic review is to synthesize the influence cooling modality has on survival with and without medical complications from exertional heat stroke (EHS) in sport and military populations. Methods and Materials: All peer-reviewed case reports or series involving EHS patients were searched in the following online databases: PubMed, Scopus, SPORTDiscus, Medline, CINAHL, Academic Search Premier, and the Cochrane Library: Central Registry of Clinical Trials. Cooling methods were subdivided into "adequate" (>0.15 °C/min) versus "insufficient" (<0.15 °C/min) based on previously published literature on EHS cooling rates. Results: 613 articles were assessed for quality and inclusion in the review. Thirty-two case reports representing 521 EHS patients met the inclusion criteria. Four hundred ninety-eight (498) patients survived EHS (95.58%) and 23 (4.41%) patients succumbed to complications. Fischer's Exact test on 2 × 2 contingency tables and relative risk ratios were calculated to determine if modality cooling rate was associated with patient outcomes. EHS patients that survived who were cooled with an insufficient cooling rate had a 4.57 times risk of medical complications compared to patients who were treated by adequate cooling methods, regardless of setting (RR = 4.57 (95%CI: 3.42, 6.28)). Conclusions: This is the largest EHS dataset yet compiled that analyzes the influence of cooling rate on patient outcomes. Zero patients died (0/521, 0.00%) when treatment included a modality with an adequate cooling rate. Conversely, 23 patients died (23/521, 4.41%) with insufficient cooling. One hundred seventeen patients (117/521, 22.46%) survived with medical complications when treatment involved an insufficient cooling rate, whereas, only four patients had complications (4/521, 0.77%) despite adequate cooling. Cooling rates >0.15 °C/min for EHS patients were significantly associated with surviving EHS without medical complications. In order to provide the best standard of care for EHS patients, an aggressive cooling rate >0.15 °C/min can maximize survival without medical complications after exercise-induced hyperthermia.
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Golpe de Calor , Esportes , Temperatura Baixa , Exercício Físico , Febre , Golpe de Calor/terapia , HumanosRESUMO
Background and Objectives: Exertional heat stroke (EHS) survivors may be more susceptible to subsequent EHS; however, the occurrence of survivors with subsequent EHS episodes is limited. Therefore, the purpose of this study was to evaluate the incidence of participants with repeated EHS (EHS-2+) cases in a warm-weather road race across participation years compared to those who experienced 1 EHS (EHS-1). Materials and Methods: A retrospective observational case series design was utilized. Medical record data from 17-years at the Falmouth Road Race between 2003-2019 were examined for EHS cases. Incidence of EHS-2+ cases per race and average EHS cases per EHS-2+ participant were calculated (mean ± SD) and descriptive factors (rectal temperature (TRE), finish time (FT), Wet Bulb Globe Temperature (WBGT), age, race year) for each EHS was collected. Results: A total of 333 EHS patients from 174,853 finishers were identified. Sixteen EHS-2+ participants (11 males, 5 females, age = 39 ± 16 year) accounted for 11% of the total EHS cases (n = 37/333). EHS-2+ participants had an average of 2.3 EHS cases per person (range = 2-4) and had an incidence rate of 2.6 EHS per 10 races. EHS-2+ participants finished 93 races following initial EHS, with 72 of the races (77%) completed without EHS incident. Initial EHS TRE was not statistically different than subsequent EHS initial TRE (+0.3 ± 0.9 °C, p > 0.050). Initial EHS-2+ participant FT was not statistically different than subsequent EHS FT (-4.2 ± 7.0 min, p > 0.050). The years between first and second EHS was 3.6 ± 3.5 year (Mode: 1, Range: 1-12). Relative risk ratios revealed that EHS patients were at a significantly elevated risk for subsequent EHS episodes 2 years following their initial EHS (relative risk ratio = 3.32, p = 0.050); however, the risk from 3-5 years post initial EHS was not statistically elevated, though the relative risk ratio values remained above 1.26. Conclusions: These results demonstrate that 11% of all EHS cases at the Falmouth Road Race are EHS-2+ cases and that future risk for a second EHS episode at this race is most likely to occur within the first 2 years following the initial EHS incident. After this initial 2-year period, risk for another EHS episode is not significantly elevated. Future research should examine factors to explain individuals who are susceptible to multiple EHS cases, incidence at other races and corresponding prevention strategies both before and after initial EHS.
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Golpe de Calor , Corrida , Adulto , Feminino , Golpe de Calor/epidemiologia , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Tempo (Meteorologia) , Adulto JovemRESUMO
BACKGROUND: Recent investigations have questioned the role of hydration and electrolytes in cramp susceptibility and thus the efficacy of consuming electrolyte-rich carbohydrate beverages (EB) to control/prevent cramping. METHODS: Nine euhydrated, cramp-prone participants had their cramp susceptibility assessed by measuring the nerve stimulation threshold frequency at which cramping occurs (TF) before and after consumption of an EB (kCal: 120, Na: 840 mg, K: 320 mg, Mg: 5 mg) and placebo beverage (PB: kCal: 5, Na: 35 mg). Cramp intensity was assessed using a verbal pain scale and poststimulation electromyography (EMG). RESULTS: TF was greater in EB (14.86 ± 7.47 Hz) than PB (14.00 ± 5.03 Hz; P = .038) and reported pain was lower in EB (2.0 ± 0.6) than PB (2.7 ± 0.8; P = .025) while EMG was similar (P = .646). DISCUSSION: EB consumption decreased cramp susceptibility and pain but did not prevent cramping in any participants. These results suggest that electrolyte consumption independent of hydration can influence cramp susceptibility in young people.
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Bebidas , Eletrólitos/uso terapêutico , Cãibra Muscular/prevenção & controle , Nervo Tibial , Adulto , Alanina/uso terapêutico , Sacarose Alimentar/uso terapêutico , Estimulação Elétrica/métodos , Eletromiografia , Feminino , Humanos , Magnésio/uso terapêutico , Masculino , Músculo Esquelético , Medição da Dor , Potássio/uso terapêutico , Sódio/uso terapêutico , Adulto JovemRESUMO
Exertional heat illness (EHI) risk is a serious concern among athletes, laborers, and warfighters. US Governing organizations have established various activity modification guidelines (AMGs) and other risk mitigation plans to help ensure the health and safety of their workers. The extent of metabolic heat production and heat gain that ensue from their work are the core reasons for EHI in the aforementioned population. Therefore, the major focus of AMGs in all settings is to modulate the work intensity and duration with additional modification in adjustable extrinsic risk factors (e.g., clothing, equipment) and intrinsic risk factors (e.g., heat acclimatization, fitness, hydration status). Future studies should continue to integrate more physiological (e.g., valid body fluid balance, internal body temperature) and biometeorological factors (e.g., cumulative heat stress) to the existing heat risk assessment models to reduce the assumptions and limitations in them. Future interagency collaboration to advance heat mitigation plans among physically active population is desired to maximize the existing resources and data to facilitate advancement in AMGs for environmental heat.
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Exercício Físico , Transtornos de Estresse por Calor/prevenção & controle , Temperatura Alta , Aclimatação , Atletas , Guias como Assunto , Humanos , Militares , Saúde Ocupacional , Estados UnidosRESUMO
Adams, EL, Casa, DJ, Huggins, RA, DeMartini-Nolan, JK, Stearns, RL, Kennedy, RM, Bosworth, MM, DiStefano, LJ, Armstrong, LE, and Maresh, CM. Heat exposure and hypohydration exacerbate physiological strain during load carrying. J Strength Cond Res 33(3): 727-735, 2019-Heat exposure and hypohydration induce physiological and psychological strain during exercise; however, it is unknown if the separate effects of heat exposure and hypohydration are synergistic when co-occurring during loaded exercise. This study compared separate and combined effects of heat exposure and hypohydration on physiological strain, mood state, and visual vigilance during loaded exercise. Twelve men (mean ± SD; age, 20 ± 2 years; body mass, 74.0 ± 8.2 kg; maximal oxygen uptake, 57.0 ± 6.0 ml·kg·min) completed 4 trials under the following conditions: euhydrated temperate (EUT), hypohydrated temperate (HYT), euhydrated hot (EUH), and hypohydrated hot (HYH). Exercise was 90 minutes of treadmill walking (â¼50% V[Combining Dot Above]O2max, 5% grade) while carrying a 45-lb rucksack. Profile of Mood States and the Scanning Visual Vigilance Test were completed before and after exercise. The separate effects of heat exposure (EUH) and hypohydration (HYT) on post-exercise rectal temperature (Tre) were similar (38.25 ± 0.63°C vs. 38.22 ± 0.29°C, respectively, p > 0.05), whereas in combination (HYH), post-exercise Tre was far greater (39.32 ± 0.43°C). Increase in Tre per 1% body mass loss (BML) for HYH (vs. EUH) was greater than HYT (vs. EUT) (0.32 vs. 0.04°C, respectively, p = 0.02); heart rate increase per 1% BML for HYH (vs. EUH) was 7 b·min compared with HYT (vs. EUT) at 3 b·min (p = 0.30). Hypohydrated hot induced greater mood disturbance (post-exercise - pre-exercise) (35 ± 21 units) compared with other conditions (EUT = 3 ± 9 units; HYT = 3 ± 16 units; EUH = 16 ± 26 units; p < 0.001). No differences occurred in visual vigilance (p > 0.05). Independently, heat exposure and hypohydration induced similar physiological strain during loaded exercise; when combined, heat exposure with hypohydration, synergistically exacerbated physiological strain and mood disturbance.
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Afeto/fisiologia , Desidratação/fisiopatologia , Exercício Físico/fisiologia , Temperatura Alta/efeitos adversos , Adolescente , Adulto , Teste de Esforço , Frequência Cardíaca/fisiologia , Humanos , Masculino , Adulto JovemRESUMO
Exertional heat stroke (EHS) is one of the most common causes of sudden death in athletes. It also represents a unique medical challenge to the prehospital healthcare provider due to the time sensitive nature of treatment. In cases of EHS, when cooling is delayed, there is a significant increase in organ damage, morbidity, and mortality after 30 minutes, faster than the average EMS transport and ED evaluation window. The purpose of this document is to present a paradigm for prehospital healthcare systems to minimize the risk of morbidity and mortality for EHS patients. With proper planning, EHS can be managed successfully by the prehospital healthcare provider.
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Serviços Médicos de Emergência , Golpe de Calor/diagnóstico , Golpe de Calor/terapia , Atletas , Consenso , Humanos , Hipotermia InduzidaRESUMO
To investigate the influence of estimated wet bulb globe temperature (WBGT) and the International Institute of Race Medicine (IIRM) activity modification guidelines on the incidence of exertional heat stroke (EHS) and heat exhaustion (HEx) and the ability of an on-site medical team to treat those afflicted. Medical records of EHS and HEx patients over a 17-year period from the New Balance Falmouth Road Race were examined. Climatologic data from nearby weather stations were obtained to calculate WBGT with the Australian Bureau of Meteorology (WBGTA) and Liljegren (WBGTL) models. Incidence rate (IR) of EHS, HEx, and combined total of EHS and HEx (COM) were calculated, and linear regression analyses were performed to assess the relationship between IR and WBGTA or WBGTL. One-way ANOVA was performed to compare differences in EHS, HEx, and COM incidence to four alert levels in the IIRM guidelines. Incidence of EHS, HEx, and COM was 2.12, 0.98, and 3.10 cases per 1000 finishers. WBGTA explained 48, 4, and 46% of the variance in EHS, HEx, and COM IR; WBGTL explained 63, 13, and 69% of the variance in EHS, HEx, and COM IR. Main effect of WBGTA and WBGTL on the alert levels were observed in EHS and COM IR (p < 0.05). The cumulative number of EHS patients treated did not exceed the number of cold water immersion tubs available to treat them. EHS IR increased as WBGT and IIRM alert level increased, indicating the need for appropriate risk mitigation strategies and on-site medical treatment.
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Golpe de Calor/epidemiologia , Temperatura Alta , Aniversários e Eventos Especiais , Humanos , Incidência , Massachusetts/epidemiologia , Corrida , Tempo (Meteorologia)RESUMO
DeMartini-Nolan, JK, Martschinske, JL, Casa, DJ, Lopez, RM, Stearns, RL, Ganio, MS, and Coris, E. Examining the influence of exercise intensity and hydration on gastrointestinal temperature in collegiate football players. J Strength Cond Res 32(10): 2888-2896, 2018-Debate exists regarding the influence of intensity and hydration on body temperature during American football. The purpose of this study was to observe body core temperature responses with changes in intensity and hydration. Twenty-nine male football players (age = 21 ± 1 year, height = 187 ± 9 cm, mass = 110.1 ± 23.5 kg, body mass index [BMI] = 31.3 ± 5.0, and body surface area [BSA] = 2.34 ± 0.27 m) participated in 8 days of practice in a warm environment (wet bulb globe temperature: 29.6 ± 1.6° C). Participants were identified as starters (S; n = 12) or nonstarters (n = 17) and linemen (L; n = 14) or nonlinemen (NL; n = 15). Variables of interest included core body temperature (T), hydration status, and physical performance characteristics as measured by a global positioning system. Intensity measures of average heart rate (138 ± 9 bpm), low-velocity movement (4.2 ± 1.7%), high-velocity movement (0.6 ± 0.6%), and average velocity (0.36 ± 0.10 m·s) accounted for 42% of the variability observed in T (38.32 ± 0.34° C, r = 0.65, p = 0.01). Hydration measures (percent body mass loss = -1.56 ± 0.80%, urine specific gravity [Usg] = 1.025 ± 0.006, and urine color [Ucol] = 6 ± 1) did not add to the prediction of T (p = 0.83). Metrics of exercise intensity accounted for 39% of the variability observed in maximum T (38.83 ± 0.42° C, r = 0.62, p = 0.02). Hydration measures did not add to this prediction (p = 0.40). Low-velocity movement, high-velocity movement, average velocity, BMI, and BSA were significantly different (p = 0.002, p < 0.001, p = 0.02, p < 0.001, p < 0.001, respectively) between L vs. NL. Heart rate and T were not different between L and NL (p > 0.05). Exercise intensity primarily accounted for the rise in core body temperature. Although L spent less time at higher velocities, T was similar to NL, suggesting that differences in BMI and BSA added to thermoregulatory strain.
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Regulação da Temperatura Corporal , Temperatura Corporal , Futebol Americano/fisiologia , Estado de Hidratação do Organismo , Índice de Massa Corporal , Sistemas de Informação Geográfica , Frequência Cardíaca , Temperatura Alta , Humanos , Masculino , Universidades , Adulto JovemRESUMO
Lopez, RM, Casa, DJ, Jensen, K, Stearns, RL, DeMartini, JK, Pagnotta, KD, Roti, MW, Armstrong, LE, and Maresh, CM. Comparison of two fluid replacement protocols during a 20-km trail running race in the heat. J Strength Cond Res 30(9): 2609-2616, 2016-Proper hydration is imperative for athletes striving for peak performance and safety, however, the effectiveness of various fluid replacement strategies in the field setting is unknown. The purpose of this study was to investigate how two hydration protocols affect physiological responses and performance during a 20-km trail running race. A randomized, counter-balanced, crossover design was used in a field setting (mean ± SD: WBGT 28.3 ± 1.9° C). Well-trained male (n = 8) and female (n = 5) runners (39 ± 14 years; 175 ± 9 cm; 67.5 ± 11.1 kg; 13.4 ± 4.6% BF) completed two 20-km trail races (5 × 4-km loop) with different water hydration protocols: (a) ad libitum (AL) consumption and (b) individualized rehydration (IR). Data were analyzed using repeated measures ANOVA. Paired t-tests compared pre-race-post-race measures. Main outcome variables were race time, heart rate (HR), gastrointestinal temperature (TGI), fluid consumed, percent body mass loss (BML), and urine osmolality (Uosm). Race times between groups were similar. There was a significant condition × time interaction (p = 0.048) for HR, but TGI was similar between conditions. Subjects replaced 30 ± 14% of their water losses in AL and 64 ± 16% of their losses in IR (p < 0.001). Ad libitum trial experienced greater BML (-2.6 ± 0.5%) compared with IR (-1.3 ± 0.5%; p < 0.001). Pre-race to post-race Uosm differences existed between AL (-273 ± 146 mOsm) and IR (-145 ± 215 mOsm, p = 0.032). In IR, runners drank twice as much fluid than AL during the 20-km race, leading to > 2% BML in AL. Ad libitum drinking resulted in 1.3% greater BML over the 20-km race, which resulted in no thermoregulatory or performance differences from IR.
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Desidratação/prevenção & controle , Hidratação/métodos , Corrida/fisiologia , Água/administração & dosagem , Adulto , Desempenho Atlético/fisiologia , Temperatura Corporal , Estudos Cross-Over , Ingestão de Líquidos/fisiologia , Feminino , Frequência Cardíaca , Temperatura Alta , Humanos , Masculino , Pessoa de Meia-Idade , Concentração Osmolar , Urina/química , Equilíbrio Hidroeletrolítico , Redução de Peso , Adulto JovemAssuntos
Golpe de Calor , Temperatura Baixa , Golpe de Calor/terapia , Humanos , Esforço Físico , Padrões de ReferênciaRESUMO
CONTEXT: A high number of exertional heat stroke (EHS) cases occur during the Falmouth Road Race. OBJECTIVES: To extend previous analyses of EHS cases during the Falmouth Road Race by assessing or describing (1) EHS and heat exhaustion (HE) incidence rates, (2) EHS outcomes as they relate to survival, (3) the effect of the environment on these outcomes, and (4) how this influences medical provider planning and preparedness. DESIGN: Descriptive epidemiologic study. SETTING: Falmouth Road Race. PATIENTS OR OTHER PARTICIPANTS: Patients with EHS or HE admitted to the medical tent. MAIN OUTCOME MEASURE(S): We obtained 8 years (2012 to 2019) of Falmouth Road Race anonymous EHS and HE medical records. Meteorologic data were collected and analyzed to evaluate the effect of environmental conditions on the heat illness incidence (exertional heat illness [EHI] = EHS + HE). The EHS treatment and outcomes (ie, cooling time, survival, and discharge outcome), number of HE patients, and wet bulb globe temperature (WBGT) for each race were analyzed. RESULTS: A total of 180 EHS and 239 HE cases were identified. Overall incidence rates per 1000 participants were 2.07 for EHS and 2.76 for HE. The EHI incidence rate was 4.83 per 1000 participants. Of the 180 EHS cases, 100% survived, and 20% were transported to the emergency department. The WBGT was strongly correlated with the incidence of both EHS (r2 = 0.904, P = .026) and EHI (r2 = 0.912, P = .023). CONCLUSIONS: This is the second-largest civilian database of EHS cases reported. When combined with the previous dataset of EHS survivors from this race, it amounts to 454 EHS cases resulting in 100% survival. The WBGT remained a strong predictor of EHS and EHI cases. These findings support 100% survival from EHS when patients over a wide range of ages and sexes are treated with cold-water immersion.
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Transtornos de Estresse por Calor , Golpe de Calor , Humanos , Temperatura Baixa , Transtornos de Estresse por Calor/epidemiologia , Golpe de Calor/epidemiologia , Golpe de Calor/terapia , Golpe de Calor/etiologia , Incidência , Água , Masculino , FemininoRESUMO
BACKGROUND: Maximal oxygen uptake (VO2max) is an important determinant of endurance performance. Heat acclimation/acclimatization (HA/HAz) elicits improvements in endurance performance. Upon heat exposure reduction, intermittent heat training (IHT) may alleviate HA/HAz adaptation decay; however, corresponding VO2max responses are unknown. HYPOTHESIS: VO2max is maintained after HAz/HA; IHT mitigates decrements in aerobic power after HAz/HA. STUDY DESIGN: Interventional study. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 27 male endurance runners (mean ± SD; age, 36 ± 12 years; body mass, 73.03 ± 8.97 kg; height, 178.81 ± 6.39 cm) completed VO2max testing at 5 timepoints; baseline, post-HAz, post-HA, and weeks 4 and 8 of IHT (IHT4, IHT8). After baseline testing, participants completed HAz, preceded by 5 days of HA involving exercise to induce hyperthermia for 60 minutes in the heat (ambient temperature, 39.13 ± 1.37°C; relative humidity, 51.08 ± 8.42%). Participants were assigned randomly to 1 of 3 IHT groups: once-weekly, twice-weekly, or no IHT. Differences in VO2max, velocity at VO2max (vVO2), and maximal heart rate (HRmax) at all 5 timepoints were analyzed using repeated-measure analyses of variance with Bonferroni corrections post hoc. RESULTS: No significant VO2max or vVO2 differences were observed between baseline, post-HAz, or post-HA (P = 0.36 and P = 0.09, respectively). No significant group or time effects were identified for VO2max or vVO2 at post-HA, IHT4, and IHT8 (P = 0.67 and P = 0.21, respectively). Significant HRmax differences were observed between baseline and post-HA tests (P < 0.01). No significant group or time HRmax differences shown for post-HA, IHT4, and IHT8 (P = 0.59). CONCLUSION: VO2max was not reduced among endurance runners after HA/HAz and IHT potentially due to participants' similar aerobic training status and high aerobic fitness levels. CLINICAL RELEVANCE: HAz/HA and IHT maintain aerobic power in endurance runners, with HAz/HA procuring reductions in HRmax.
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CONTEXT: Little information exists regarding what exertional heatstroke (EHS) survivors know and believe about EHS best practices. Understanding this would help clinicians focus educational efforts to ensure survival and safe return-to-play following EHS. OBJECTIVE: We sought to better understand what EHS survivors knew about EHS seriousness (e.g., lethality, short- and long-term effects), diagnosis and treatment procedures, and recovery. Design: Multi-year, cross-sectional, descriptive design. SETTING: An 11.3-km road race located in the Northeastern United States in August 2022 and 2023. PATIENTS OR OTHER PARTICIPANTS: Forty-two of 62 runners with EHS (15 women, 27 men; age: 33±15 y; pre-treatment rectal temperature [TREC]: 41.5±0.9°C). INTERVENTIONS: Medical professionals evaluated runners requiring medical attention at the finish line. If they observed TREC ≥40°C with concomitant central nervous system dysfunction (CNS) EHS was diagnosed and patients were immersed in a 189.3-L tub filled with ice-water. Before medical discharge, we asked EHS survivors 15 questions about their experience and knowledge of select EHS best practices. Survey items were piloted and validated by experts and laypersons a priori (content validity index ≥0.88 for items and scale). MAIN OUTCOME MEASURES: Survey responses. RESULTS: Sixty-seven percent (28/42) of patients identified EHS as potentially fatal and 76% (32/42) indicated it negatively affected health. Seventy-nine percent (33/42) correctly identified TREC as the best temperature site to diagnose EHS. Most patients (74%, 31/42) anticipated returning to normal exercise within 1 week post-EHS; 69% (29/42) stated EHS would not impact future race participation. Patients (69%, 29/42) indicated it was important to tell their primary care physician about their EHS. CONCLUSIONS: Our patients were knowledgeable on the potential seriousness and adverse health effects of EHS and the necessity of TREC for diagnosis. However, educational efforts should be directed towards helping patients understand safe recovery and return-to-play timelines following EHS.