Journal articles: 'Exertional heat stress'

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Ogden, Henry B., Robert B. Child, Joanne L. Fallowfield, Simon K. Delves, Caroline S. Westwood, and Joseph D. Layden. "The Gastrointestinal Exertional Heat Stroke Paradigm: Pathophysiology, Assessment, Severity, Aetiology and Nutritional Countermeasures." Nutrients 12, no. 2 (February 19, 2020): 537. http://dx.doi.org/10.3390/nu12020537.

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Exertional heat stroke (EHS) is a life-threatening medical condition involving thermoregulatory failure and is the most severe condition along a continuum of heat-related illnesses. Current EHS policy guidance principally advocates a thermoregulatory management approach, despite growing recognition that gastrointestinal (GI) microbial translocation contributes to disease pathophysiology. Contemporary research has focused to understand the relevance of GI barrier integrity and strategies to maintain it during periods of exertional-heat stress. GI barrier integrity can be assessed non-invasively using a variety of in vivo techniques, including active inert mixed-weight molecular probe recovery tests and passive biomarkers indicative of GI structural integrity loss or microbial translocation. Strenuous exercise is strongly characterised to disrupt GI barrier integrity, and aspects of this response correlate with the corresponding magnitude of thermal strain. The aetiology of GI barrier integrity loss following exertional-heat stress is poorly understood, though may directly relate to localised hyperthermia, splanchnic hypoperfusion-mediated ischemic injury, and neuroendocrine-immune alterations. Nutritional countermeasures to maintain GI barrier integrity following exertional-heat stress provide a promising approach to mitigate EHS. The focus of this review is to evaluate: (1) the GI paradigm of exertional heat stroke; (2) techniques to assess GI barrier integrity; (3) typical GI barrier integrity responses to exertional-heat stress; (4) the aetiology of GI barrier integrity loss following exertional-heat stress; and (5) nutritional countermeasures to maintain GI barrier integrity in response to exertional-heat stress.

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Stojićević, Jelena, and Vanja Jovanović. "The effects of exertional heat stress on some complex cognitive functions." Praxis medica 50, no. 3-4 (2021): 13–16. http://dx.doi.org/10.5937/pramed2104013s.

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Introduction/Aim: Heat stress represents the important problem in military services. This study investigates the effects of exertional heat stress on complex cognitive functions. Methods: 40 male soldiers performed exertional heat stress test, of which 10 performed the test of the same intensity in cool environment. Cognitive functions were mesured by computerized battery CANTAB, before and immediately after exertional heat stress test. Results: Exertional heat stress led to impairment of some cognitive functions in unacclimatized group: decrease of accuracy in MTS test (from 92,6±4,2% towards 84,5±6,9%, p<0,05) and PSRs (from 85,0±8,0% towards 77,0±9,6%, p<0,05), while similar decreases were recorded in MTS test in passively acclimatized group (from 92,2±5,5% towards 87,7±5,6%, p<0,05) i.e. in PSRs test in actively acclimatized group (from 83,3±6,3% towards 69,4±5,1%, p<0,05). The reaction time was not affected in any group whatsoever. Discussion and conclusion: Exertional heat stress leads to mild impairment of complex cognitive functions, particularly in domain of accuracy. Physical strain itself, however, does not affect cognitive functions. Relatively resistance to heat stress in zoung soldiers may be contributed to their high aerobic level.

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Radakovic, Sonja, Jelena Maric, Velimir Rubezic, Maja Surbatovic, and Slavica Radjen. "Effects of acclimation on water and electrolitic disbalance in soldiers during exertional heat stress." Vojnosanitetski pregled 64, no. 3 (2007): 199–204. http://dx.doi.org/10.2298/vsp0703199r.

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Background/Aim. Exertional heat stress is a common problem in military services. The aim of this study was to examine changes in body water and serum concentrations of some electrolites in soldiers during exertional heat stress (EHST), as well as effects of 10-day passive or active acclimation in a climatic chamber. Methods. Forty male soldiers with high aerobic capacity, performed EHST either in cool (20 ?C, 16 ?C WBGT-wet bulb globe temperature), or hot (40 ?C, 25 ?C WBGT) environment, unacclimatized, or after 10 days of passive or active acclimation. The subjects were allowed to drink tap water ad libitum during EHST. Mean skin (Tsk) and tympanic (Tty) temperatures and heart rates (HR) measured physiological strain, while sweat rate (SwR), and serum concentrations of sodium, potassium and osmolality measured changes in water and electrolyte status. Blood samples were collected before and immediately after the EHST. Results. Exertional heat stress in hot conditions induced physiological heat stress (increase in Tty, HR, and SwR), with significant decrease in serum sodium concentration (140.6?1.52 before vs 138.5?1.0 mmol/l after EHST, p < 0.01) and osmolality (280.7?3.8 vs 277.5?2.6 mOsm/kg, p < 0.05) in the unacclimatized group. The acclimated soldiers suffered no such effects of exertional heat stress, despite almost the same degree of heat strain, measured by Tty, HR and SwR. Conclusion. In the trained soldiers, 10-day passive or active acclimation in a climatic chamber can prevent disturbances in water and electrolytic balance, i.e. decrease in serum sodium concentrations and osmolality induced by exertional heat stress.

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Masic, Sinisa, Sonja Marjanovic, Jelena Maric, Vanja Jovanovic, Mirjana Joksimovic, and Danijela Ilic. "Relationship between heat storage and parameters of thermotolerance and fatigue in exertional-heat stress." Vojnosanitetski pregled, no. 00 (2021): 99. http://dx.doi.org/10.2298/vsp211012099m.

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Background/Aim. The risk assessment of heat illness and fatigue development is very important in military services. the aim of our study was to investigate the relationship between heat storage and various psychophysiological parameters of heat stress, as well as potential peripheral markers of fatigue in soldiers performing exertional heat stress test. Methods. 15 young, healthy and unacclimatized men underwent exertional heat stress test (EHST) with submaximal work load in warm conditions (WBGT 29 ?C) in climatic chamber. Every 5 minutes following parameters of thermotolerance were measured or calculated: core temperature (Tc), mean skin (Tsk) and body temperature (Tb), heart rate (HR), heat storage (HS), physiological strain index (PSI), as well as peripheral markers of fatigue (blood concentrations of ammonia, urea nitrogen (BUN), lactate dehydrogenase (LDH), cortisol and prolactin) and subjective parameters: thermal sensation (TS) and rate of perceived exertion (RPE). Results. Tolerance time varied from 45-75 minutes (63?7,7 min). Average values of Tc, Tb, and HR constantly increased during EHST, while Tsk after 10 minutes reached the plateau. Concentrations of all investigated peripheral markers of fatigue were significantly higher after EHST compared to baseline levels (31,47?7,29 vs. 11,8?1,11 ?mol/l for ammonia; 5,92?0,73 vs. 4,69?0,74 mmol/l for BUN, 187,27?28,49 vs.152,73?23,39 U/l for LDH, 743,43?206,19 vs. 558,79?113,34 mmol/l for cortisol and 418,08?157,14 vs. 138,79?92,83 ?IU/mL for prolactin). Conclusions. This study demonstrates the relationship between heat storage and Tc, HR, TS and RPE, but also with PSI. Concentrations of cortisol and especially prolactin showed significant correlation with parameters of thermotolerance.

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Flouris, Andreas D., Andrea Bravi, Heather E. Wright-Beatty, Geoffrey Green, Andrew J. Seely, and Glen P. Kenny. "Heart rate variability during exertional heat stress: effects of heat production and treatment." European Journal of Applied Physiology 114, no. 4 (January 5, 2014): 785–92. http://dx.doi.org/10.1007/s00421-013-2804-7.

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Radakovic, Sonja, Jelena Maric, Maja Surbatovic, Nadja Vasiljevic, and Mladen Milivojevic. "Influence of acclimatization on serum enzyme changes in soldiers during exertional heat stress." Vojnosanitetski pregled 66, no. 5 (2009): 359–64. http://dx.doi.org/10.2298/vsp0905359r.

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Background/Aim. Exertional heat stress is common problem in military services. The aim was to examine changes in serum concentrations of some enzymes in soldiers during exertional heat stress test (EHST) as well as the effects of 10-days passive or active acclimatization in climatic chamber. Methods. Forty male soldiers with high aerobic capacity, performed EHST either in cool (20 ?C, 16 ?C Wet bulb globe temperature - WBGT), or hot (40 ?C, 25 ?C WBGT) environment, unacclimatized, or after 10 days of passive or active acclimation. Physiological strain was measured by tympanic temperatures (Tty) and heart rates (HR). Concentrations of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and creatine-kinase (CK) were measured in blood samples collected before and immediately after EHST. Results. Exertional heat stress test in hot conditions induced physiological heat stress (increase in Tty and HR), with significant increase in concentrations of all enzymes in unacclimatized group: ALT (42.5 ? 4.2 before vs 48.1 ? 3.75 U/L after EHST, p < 0.01), AST (24.9 ? 5.1 vs 33.4 ? 4.48 U/L, p < 0.01), LDH (160.6 ? 20.2 vs 195.7 ? 22.6 U/L, p < 0.001) and CK (215.5 ? 91.2 vs 279.1 ? 117.5 U/L, p < 0.05). In acclimatized soldiers there were no significant changes in concentrations of ALT and AST, while concentration of CK was significantly higher. Concentrations of LDH were significantly higher in all investigated groups, regardless of temperature conditions. Conclusion. In trained soldiers, 10-days passive or active acclimatization in climatic chamber can prevent increase in serum concentrations of ALT and AST, induced by exertional heat stress. Increase of serum concentrations of CK and LDH was induced by physical strain itself, with no additional effect of heat stress.

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Maric, Jelena, Milan Marjanovic, Dalibor Jovanovic, Filip Stojanovic, Djordje Vukmirovic, and Vladimir Jakovljevic. "Simple And Complex Cognitive Functions Under Exertional Heat Stress." Serbian Journal of Experimental and Clinical Research 16, no. 1 (March 1, 2015): 21–25. http://dx.doi.org/10.1515/sjecr-2015-0003.

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ABSTRACTHeat stress is a significant problem in the military services. This study investigated the effects of exertional heat stress on cognitive performance.Forty unacclimated male soldiers performed exertional heat stress tests in cool (20 °C) and hot environments (40 °C). Cognitive performance was assessed using a computerized battery before and immediately after tests. Physical strain in cool conditions induced mild but significant deficits in accuracy in complex tests. The number of correct answers in the Matching to Sample Visual Search was reduced (92,18% correct answers before vs. 88,64 after; p<0,05) and also in the spatial part of the Pattern and Spatial Recognition Memory Test (85,25 vs. 8,75%; p<0,05). These decreases were more pronounced in hot conditions (92,38 vs. 84,31% in before and 84,21 vs. 73,42% in the latter test; ps<0,01 and <0,001, respectively). Exertional heat stress also impaired more simple cognitive functions. A significant decrease in accuracy (95,74 vs. 93,89%) and an increase in reaction time (300,32 vs. 315,00 ms) was observed in the Reaction Time test.Strenuous physical activity in a hot environment induces mild cognitive deficits, especially in more complex tasks.

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Vesic, Zoran, Milica Vukasinovic-Vesic, Dragan Dincic, Maja Surbatovic, and Sonja Radakovic. "The effects of acclimatization on blood clotting parameters in exertional heat stress." Vojnosanitetski pregled 70, no. 7 (2013): 670–74. http://dx.doi.org/10.2298/vsp120630013v.

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Background/Aim. Exertional heat stress is a common problem in military services. Considering the coagulation abnormalities are of major importance in development of severe heat stroke, we wanted to examine changes in hemostatic parameters in soldiers during exertional heat stress test as well as the effects of a 10-day passive or active acclimatization in a climatic chamber. Methods. A total of 40 male soldiers with high aerobic capacity performed exertional heat stress test (EHST) either in cool [20?C, 16?C wet bulb globe temperature (WBGT)], or hot (40?C, 29?C, (WBGT) environment, unacclimatized (U) or after 10 days of passive (P) or active (A) acclimatization. Physiological strain was measured by tympanic temperatures (Tty) and heart rates (HR). Platelet count (PC), antithrombin III (AT), and prothrombin time (PT) were assessed in blood samples collected before and immediately after the EHST. Results. EHST in hot conditions induced physiological heat stress (increase in Tty and HR), with a significant increase in prothrombin time in the groups U and A. Platelet counts were significantly higher after the EHST compared to the basic levels in all the investigated groups, regardless environmental conditions and acclimatization state. Antithrombin levels were not affected by EHST whatsoever. Conclusion. In the trained soldiers, physiological heat stress caused mild changes in some serum parameters of blood clotting such as prothrombin time, while others such as antithrombin levels were not affected. Platelet counts were increased after EHST in all groups. A 10-day passive or active acclimatization in climatic chamber showed no effect on parameters investigated.

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Laitano, Orlando, Christian K. Garcia, Alex J. Mattingly, Gerard P. Robinson, Kevin O. Murray, Michelle King, Brian Ingram, Sivapriya Ramamoorthy, Lisa R. Leon, and Thomas L. Clanton. "Stress‐Induced Cardiomyopathy Following Exertional Heat Stroke in Mice." FASEB Journal 34, S1 (April 2020): 1. http://dx.doi.org/10.1096/fasebj.2020.34.s1.02108.

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Ren, Ming Qiang, Josh B. Kazman, Preetha A. Abraham, Danit Atias-Varon, Yuval Heled, and Patricia A. Deuster. "Gene expression profiling of humans under exertional heat stress: Comparisons between persons with and without exertional heat stroke." Journal of Thermal Biology 85 (October 2019): 102423. http://dx.doi.org/10.1016/j.jtherbio.2019.102423.

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Rakesh, Vineet, Jonathan D. Stallings, and Jaques Reifman. "A virtual rat for simulating environmental and exertional heat stress." Journal of Applied Physiology 117, no. 11 (December 1, 2014): 1278–86. http://dx.doi.org/10.1152/japplphysiol.00614.2014.

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Severe cases of environmental or exertional heat stress can lead to varying degrees of organ dysfunction. To understand heat-injury progression and develop efficient management and mitigation strategies, it is critical to determine the thermal response in susceptible organs under different heat-stress conditions. To this end, we used our previously published virtual rat, which is capable of computing the spatiotemporal temperature distribution in the animal, and extended it to simulate various heat-stress scenarios, including 1) different environmental conditions, 2) exertional heat stress, 3) circadian rhythm effect on the thermal response, and 4) whole body cooling. Our predictions were consistent with published in vivo temperature measurements for all cases, validating our simulations. We observed a differential thermal response in the organs, with the liver experiencing the highest temperatures for all environmental and exertional heat-stress cases. For every 3°C rise in the external temperature from 40 to 46°C, core and organ temperatures increased by ∼0.8°C. Core temperatures increased by 2.6 and 4.1°C for increases in exercise intensity from rest to 75 and 100% of maximal O2 consumption, respectively. We also found differences as large as 0.8°C in organ temperatures for the same heat stress induced at different times during the day. Even after whole body cooling at a relatively low external temperature (1°C for 20 min), average organ temperatures were still elevated by 2.3 to 2.5°C compared with normothermia. These results can be used to optimize experimental protocol designs, reduce the amount of animal experimentation, and design and test improved heat-stress prevention and management strategies.

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Kregel, K. C., and P. L. Moseley. "Differential effects of exercise and heat stress on liver HSP70 accumulation with aging." Journal of Applied Physiology 80, no. 2 (February 1, 1996): 547–51. http://dx.doi.org/10.1152/jappl.1996.80.2.547.

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Previous reports have suggested that the heat shock response to passive heating may be blunted by aging. However, during exertional heating, factors in addition to elevated temperature may amplify the degree of stress compared with hyperthermia alone. The purpose of this study was to compare the pattern of accumulation of the highly inducible 72-kDa heat shock protein (HSP72) in liver tissue of mature (12-mo-old) and senescent (24-mo-old) male Fischer 344 rats after either passive or exertional heat stress. A euthermic control group was exposed to an ambient temperature (Ta) of 25 degrees C for 4.5 h. A passive heating (heat) group was exposed to an Ta of 42 degrees C until colonic temperature (Tco) reached 41 degrees C. An exertional heating (exercise) group performed intermittent moderate-intensity treadmill exercise (similar absolute intensities for the two age groups) at an Ta of 32 degrees C until Tco reached 41 degrees C. Heating rates were similar in the heat and exercise groups (approximately 0.08 degrees C/min). Rats in both the heat and exercise groups were maintained at a Tco of 41 degrees C for an additional 30 min and subsequently returned to an Ta of 25 degrees C for 3 h. Liver HSP72 accumulation was increased in mature rats after both the heat (+192% vs. control) and exercise (+292%) protocols. In contrast, the senescent rats demonstrated no significant increase in inducible HSP70 with heating but a large increase with exercise (+232%; P < 0.01 compared with control and heat groups). These data suggest that the blunted heat shock protein response to heating observed with aging is not a result of the inability to produce inducible HSP72 because older rats had an robust response to exertional hyperthermia.

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Iftikhar, Abeer, and Hamza Sohail. "Heat stroke: what goes on at vascular level?" International Journal Of Community Medicine And Public Health 7, no. 6 (May 27, 2020): 2429. http://dx.doi.org/10.18203/2394-6040.ijcmph20202510.

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Heat stroke is the most calamitous consequence of environmental heat stress affecting every age group that can be traced back to more than 2000 years. It can be defined as a form of hyperthermia associated with a systemic inflammatory response leading to multiorgan dysfunction syndrome in which encephalopathy predominates. Based on its etiology, heat stroke can be divided into classic (resulting from exposure to high environmental temperatures) (called classic or non-exertional heat stroke) or exertional heat stroke (from strenuous exercise).

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McCubbin, Alan J., Bethanie A. Allanson, Joanne N. Caldwell Odgers, Michelle M. Cort, Ricardo J. S. Costa, Gregory R. Cox, Siobhan T. Crawshay, et al. "Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments." International Journal of Sport Nutrition and Exercise Metabolism 30, no. 1 (January 1, 2020): 83–98. http://dx.doi.org/10.1123/ijsnem.2019-0300.

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It is the position of Sports Dietitians Australia (SDA) that exercise in hot and/or humid environments, or with significant clothing and/or equipment that prevents body heat loss (i.e., exertional heat stress), provides significant challenges to an athlete’s nutritional status, health, and performance. Exertional heat stress, especially when prolonged, can perturb thermoregulatory, cardiovascular, and gastrointestinal systems. Heat acclimation or acclimatization provides beneficial adaptations and should be undertaken where possible. Athletes should aim to begin exercise euhydrated. Furthermore, preexercise hyperhydration may be desirable in some scenarios and can be achieved through acute sodium or glycerol loading protocols. The assessment of fluid balance during exercise, together with gastrointestinal tolerance to fluid intake, and the appropriateness of thirst responses provide valuable information to inform fluid replacement strategies that should be integrated with event fuel requirements. Such strategies should also consider fluid availability and opportunities to drink, to prevent significant under- or overconsumption during exercise. Postexercise beverage choices can be influenced by the required timeframe for return to euhydration and co-ingestion of meals and snacks. Ingested beverage temperature can influence core temperature, with cold/icy beverages of potential use before and during exertional heat stress, while use of menthol can alter thermal sensation. Practical challenges in supporting athletes in teams and traveling for competition require careful planning. Finally, specific athletic population groups have unique nutritional needs in the context of exertional heat stress (i.e., youth, endurance/ultra-endurance athletes, and para-sport athletes), and specific adjustments to nutrition strategies should be made for these population groups.

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Pryor, Riana R., Ronald N. Roth, Joe Suyama, and David Hostler. "Exertional Heat Illness: Emerging Concepts and Advances in Prehospital Care." Prehospital and Disaster Medicine 30, no. 3 (April 10, 2015): 297–305. http://dx.doi.org/10.1017/s1049023x15004628.

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AbstractExertional heat illness is a classification of disease with clinical presentations that are not always diagnosed easily. Exertional heat stroke is a significant cause of death in competitive sports, and the increasing popularity of marathons races and ultra-endurance competitions will make treating many heat illnesses more common for Emergency Medical Services (EMS) providers. Although evidence is available primarily from case series and healthy volunteer studies, the consensus for treating exertional heat illness, coupled with altered mental status, is whole body rapid cooling. Cold or ice water immersion remains the most effective treatment to achieve this goal. External thermometry is unreliable in the context of heat stress and direct internal temperature measurement by rectal or esophageal probes must be used when diagnosing heat illness and during cooling. With rapid recognition and implementation of effective cooling, most patients suffering from exertional heat stroke will recover quickly and can be discharged home with instructions to rest and to avoid heat stress and exercise for a minimum of 48 hours; although, further research pertaining to return to activity is warranted.PryorRR,RothRN,SuyamaJ,HostlerD.Exertional heat illness: emerging concepts and advances in prehospital care.Prehosp Disaster Med.2015;30(3):19.

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King, Michelle A., Ian Rollo, and Lindsay B. Baker. "Nutritional considerations to counteract gastrointestinal permeability during exertional heat stress." Journal of Applied Physiology 130, no. 6 (June 1, 2021): 1754–65. http://dx.doi.org/10.1152/japplphysiol.00072.2021.

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Intestinal barrier integrity and function are compromised during exertional heat stress (EHS) potentially leading to consequences that range from minor gastrointestinal (GI) disturbances to fatal outcomes in exertional heat stroke or septic shock. This mini-review provides a concise discussion of nutritional interventions that may protect against intestinal permeability during EHS and suggests physiological mechanisms responsible for this protection. Although diverse nutritional interventions have been suggested to be protective against EHS-induced GI permeability, the ingestion of certain amino acids, carbohydrates, and fluid per se is potentially effective strategy, whereas evidence for various polyphenols and pre/probiotics is developing. Plausible physiological mechanisms of protection include increased blood flow, epithelial cell proliferation, upregulation of intracellular heat shock proteins, modulation of inflammatory signaling, alteration of the GI microbiota, and increased expression of tight junction (TJ) proteins. Further clinical research is needed to propose specific nutritional candidates and recommendations for their application to prevent intestinal barrier disruption and elucidate mechanisms during EHS.

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McCubbin, Alan J. "Exertional heat stress and sodium balance: Leaders, followers, and adaptations." Autonomic Neuroscience 235 (November 2021): 102863. http://dx.doi.org/10.1016/j.autneu.2021.102863.

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Snipe, Rhiannon M. J. "Exertional heat stress-induced gastrointestinal perturbations: prevention and management strategies." British Journal of Sports Medicine 53, no. 20 (September 19, 2018): 1312–13. http://dx.doi.org/10.1136/bjsports-2018-099660.

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Karkalic, Radovan, Dalibor Jovanovic, Sonja Radakovic, Dusan Rajic, Biljana Petrovic, Negovan Ivankovic, and Zeljko Senic. "The influence of the passive evaporative cooling vest on a chemical industry workers and physiological strain level in hot conditions." Chemical Industry 69, no. 6 (2015): 587–94. http://dx.doi.org/10.2298/hemind140705079k.

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The present study was conducted in order to evaluate efficiency of a personal body cooling system based on passive evaporative technologies and its effects on test subjects psycho-physiological suitability during exertional heat stress in hot environment. Performed results are based on conducted tests in climatic chamber in the Military Medical Academy Institute of Hygiene in Belgrade. Ten male test subjects were subjected to exertional heat stress test consisted of walking on motorized treadmill at a speed of 5 km/h in hot environment. Tests were performed with and without cooling system. As a physiological strain indicator the following parameters have been determined: mean skin temperature, tympanic temperature, heart rate and sweat rate. Results confirmed that cooling vest worn over the clothes was able to attenuate the physiological strain levels during exercise, when compared to identical exposure without the cooling system.

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Johnson, Evan C., Fred W. Kolkhorst, Allen Richburg, Andy Schmitz, John Martinez, and Lawrence E. Armstrong. "Specific Exercise Heat Stress Protocol for a Triathlete’s Return from Exertional Heat Stroke." Current Sports Medicine Reports 12, no. 2 (2013): 106–9. http://dx.doi.org/10.1249/jsr.0b013e31828940f9.

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Unnikrishnan, Ginu, Rajeev Hatwar, Samantha Hornby, Srinivas Laxminarayan, Tushar Gulati, Luke N. Belval, Gabrielle E. W. Giersch, Josh B. Kazman, Douglas J. Casa, and Jaques Reifman. "A 3-D virtual human thermoregulatory model to predict whole-body and organ-specific heat-stress responses." European Journal of Applied Physiology 121, no. 9 (June 5, 2021): 2543–62. http://dx.doi.org/10.1007/s00421-021-04698-1.

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Abstract Objective This study aimed at assessing the risks associated with human exposure to heat-stress conditions by predicting organ- and tissue-level heat-stress responses under different exertional activities, environmental conditions, and clothing. Methods In this study, we developed an anatomically detailed three-dimensional thermoregulatory finite element model of a 50th percentile U.S. male, to predict the spatiotemporal temperature distribution throughout the body. The model accounts for the major heat transfer and thermoregulatory mechanisms, and circadian-rhythm effects. We validated our model by comparing its temperature predictions of various organs (brain, liver, stomach, bladder, and esophagus), and muscles (vastus medialis and triceps brachii) under normal resting conditions (errors between 0.0 and 0.5 °C), and of rectum under different heat-stress conditions (errors between 0.1 and 0.3 °C), with experimental measurements from multiple studies. Results Our simulations showed that the rise in the rectal temperature was primarily driven by the activity level (~ 94%) and, to a much lesser extent, environmental conditions or clothing considered in our study. The peak temperature in the heart, liver, and kidney were consistently higher than in the rectum (by ~ 0.6 °C), and the entire heart and liver recorded higher temperatures than in the rectum, indicating that these organs may be more susceptible to heat injury. Conclusion Our model can help assess the impact of exertional and environmental heat stressors at the organ level and, in the future, evaluate the efficacy of different whole-body or localized cooling strategies in preserving organ integrity.

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Gagnon, Daniel, Bruno B. Lemire, Ollie Jay, and Glen P. Kenny. "Aural Canal, Esophageal, and Rectal Temperatures During Exertional Heat Stress and the Subsequent Recovery Period." Journal of Athletic Training 45, no. 2 (March 1, 2010): 157–63. http://dx.doi.org/10.4085/1062-6050-45.2.157.

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Abstract Context: The measurement of body temperature is crucial for the initial diagnosis of exertional heat injury and for monitoring purposes during a subsequent treatment strategy. However, little information is available about how different measurements of body temperature respond during and after exertional heat stress. Objective: To present the temporal responses of aural canal (Tac), esophageal (Tes), and rectal (Tre) temperatures during 2 different scenarios (S1, S2) involving exertional heat stress and a subsequent recovery period. Design: Randomized controlled trial. Setting: University research laboratory. Patients or Other Participants: Twenty-four healthy volunteers, with 12 (5 men, 7 women) participating in S1 and 12 (7 men, 5 women) participating in S2. Intervention(s): The participants exercised in the heat (42°C, 30% relative humidity) until they reached a 39.5°C cut-off criterion, which was determined by Tre in S1 and by Tes in S2. As such, participants attained different levels of hyperthermia (as determined by Tre) at the end of exercise. Participants in S1 were subsequently immersed in cold water (2°C) until Tre reached 37.5°C, and participants in S2 recovered in a temperate environment (30°C, 30% relative humidity) for 60 minutes. Main Outcome Measure(s): We measured Tac, Tes, and Tre throughout both scenarios. Results: The Tes (S1 = 40.19 ± 0.41°C, S2 = 39.50 ± 0.02°C) was higher at the end of exercise compared with both Tac (S1 = 39.74 ± 0.42°C, S2 = 38.89 ± 0.32°C) and Tre (S1 = 39.41 ± 0.04°C, S2 = 38.74 ± 0.28°C) (for both comparisons in each scenario, P < .001). Conversely, Tes (S1 = 36.26 ± 0.74°C, S2 = 37.36 ± 0.34°C) and Tac (S1 = 36.48 ± 1.07°C, S2 = 36.97 ± 0.38°C) were lower compared with Tre (S1 = 37.54 ± 0.04°C, S2 = 37.78 ± 0.31°C) at the end of both scenarios (for both comparisons in each scenario, P < .001). Conclusions: We found that Tac, Tes, and Tre presented different temporal responses during and after both scenarios of exertional heat stress and a subsequent recovery period. Although these results may not have direct practical implications in the field monitoring and treatment of individuals with exertional heat injury, they do quantify the extent to which these body temperature measurements differ in such scenarios.

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Wright, Heather E., and Tom M. McLellan. "Central Fatigue Indicators during Repeated Exertional Heat Stress in Untrained Males." Medicine & Science in Sports & Exercise 42 (May 2010): 79–800. http://dx.doi.org/10.1249/01.mss.0000386472.23761.e1.

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McLellan, Tom M., Glen A. Selkirk, Heather E. Wright, Shawn G. Rhind, and Ira Jacobs. "Cytoprotection Against Apoptosis Following An Acute Bout Of Exertional Heat Stress." Medicine & Science in Sports & Exercise 38, Supplement (May 2006): S308. http://dx.doi.org/10.1249/00005768-200605001-02202.

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Wright, Heather E., Tom M. McLellan, Glen A. Selkirk, and Ira Jacobs. "Neuroendocrine Response In Trained Versus Untrained Individuals During Exertional Heat Stress." Medicine & Science in Sports & Exercise 38, Supplement (May 2006): S485. http://dx.doi.org/10.1249/00005768-200605001-02903.

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Szymanski, Mandy C., Trevor L. Gillum, Lacey M. Gould, David S. Morin, and Matthew R. Kuennen. "Short-term dietary curcumin supplementation reduces gastrointestinal barrier damage and physiological strain responses during exertional heat stress." Journal of Applied Physiology 124, no. 2 (February 1, 2018): 330–40. http://dx.doi.org/10.1152/japplphysiol.00515.2017.

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This work investigated the effect of 3 days of 500 mg/day dietary curcumin supplementation on gastrointestinal barrier damage and systems-physiology responses to exertional heat stress in non-heat-acclimated humans. Eight participants ran (65% V̇o2max) for 60 min in a Darwin chamber (37°C/25% relative humidity) two times (Curcumin/Placebo). Intestinal fatty acid-binding protein (I-FABP) and associated proinflammatory [monocyte chemoattractant protein-1, tumor necrosis factor-α (TNF-α), interleukin-6] and anti-inflammatory [interleukin-1 receptor antagonist (IL-1RA), interleukin-10 (IL-10)] cytokines were assayed from plasma collected before (Pre), after (Post) and 1 (1-Post) and 4 (4-Post) h after exercise. Core temperature and HR were measured throughout exercise; the physiological strain index (PSI) was calculated from these variables. Condition differences were determined with 2-way (condition × time) repeated-measures ANOVAs. The interaction of condition × time was significant ( P = 0.05) for I-FABP and IL-1RA. Post hoc analysis indicated I-FABP increased more from Pre to Post (87%) and 1-Post (33%) in Placebo than in Curcumin (58 and 18%, respectively). IL-1RA increased more from Pre to 1-Post in Placebo (153%) than in Curcumin (77%). TNF-α increased ( P = 0.01) from Pre to Post (19%) and 1-Post (24%) in Placebo but not in Curcumin ( P > 0.05). IL-10 increased ( P < 0.01) from Pre to Post (61%) and 1-Post (42%) in Placebo not in Curcumin ( P > 0.05). The PSI, which indicates exertional heatstroke risk, was also lower ( P < 0.01) in Curcumin than Placebo from 40 to 60 min of exercise. These data suggest 3 days curcumin supplementation may improve gastrointestinal function, associated cytokines, and systems-level physiology responses during exertional heat stress. This could help reduce exertional heatstroke risk in non-heat-acclimated individuals.NEW & NOTEWORTHY Exercise-heat stress increases gastrointestinal barrier damage and risk of exertional heatstroke. Over the past decade at least eight different dietary supplements have been tested for potential improvements in gastrointestinal barrier function and systems-level physiology responses during exercise-heat stress. None have been shown to protect against both insults simultaneously. In this report 3 days of 500 mg/day dietary curcumin supplementation are shown to improve gastrointestinal barrier function, associated cytokine responses, and systems-level physiology parameters. Further research is warranted.

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DeMartini, Julie K., Douglas J. Casa, Luke N. Belval, Arthur Crago, Rob J. Davis, John J. Jardine, and Rebecca L. Stearns. "Environmental Conditions and the Occurrence of Exertional Heat Illnesses and Exertional Heat Stroke at the Falmouth Road Race." Journal of Athletic Training 49, no. 4 (August 1, 2014): 478–85. http://dx.doi.org/10.4085/1062-6050-49.3.26.

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Context: The Falmouth Road Race is unique because of the environmental conditions and relatively short distance, which allow runners to maintain a high intensity for the duration of the event. Therefore, the occurrence of exertional heat illnesses (EHIs), especially exertional heat stroke (EHS), is 10 times higher than in other races. Objective: To summarize the occurrence and relationship of EHI and environmental conditions at the Falmouth Road Race. Design: Descriptive epidemiologic study. Setting: An 11.3-km (7-mile) road race in Falmouth, Massachusetts. Patients or Other Participants: Runners who sustained an EHI while participating in the Falmouth Road Race. Main Outcome Measure(s): We obtained 18 years of medical records and environmental conditions from the Falmouth Road Race and documented the incidence of EHI, specifically EHS, as related to ambient temperature (Tamb), relative humidity, and heat index (HI). Results: Average Tamb, relative humidity, and HI were 23.3 ± 2.5°C, 70 ± 16%, and 24 ± 3.5°C, respectively. Of the 393 total EHI cases observed, EHS accounted for 274 (70%). An average of 15.2 ± 13.0 EHS cases occurred each year; the incidence was 2.13 ± 1.62 cases per 1000 runners. Regression analysis revealed a relationship between the occurrence of both EHI and EHS and Tamb (R2 = 0.71, P = .001, and R2 = 0.65, P = .001, respectively) and HI (R2 = 0.76, P < .001, and R2 = 0.74, P < .001, respectively). Occurrences of EHS (24.2 ± 15.5 cases versus 9.3 ± 4.3 cases) and EHI (32.3 ± 16.3 versus 13.0 ± 4.9 cases) were higher when Tamb and HI were high compared with when Tamb and HI were low. Conclusions: Because of the environmental conditions and race duration, the Falmouth Road Race provides a unique setting for a high incidence of EHS. A clear relationship exists between environmental stress, especially as measured by Tamb and HI, and the occurrence of EHS or other EHI. Proper prevention and treatment strategies should be used during periods of high environmental temperatures as the likelihood of runners experiencing EHS is exacerbated in these harsh conditions.

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Jovanovic, Dalibor, Radovan Karkalic, Snjezana Zeba, Miroslav Pavlovic, and Sonja Radakovic. "Physiological tolerance to uncompensated heat stress in soldiers: Effects of various types of body cooling systems." Vojnosanitetski pregled 71, no. 3 (2014): 259–64. http://dx.doi.org/10.2298/vsp120731045j.

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Background/Aim. In military services, emergency situations when soldiers are exposed to a combination of nuclear, biological and chemical (NBC) contamination combined with heat stress, are frequent and complex. In these specific conditions, usage of personal body cooling systems may be effective in reducing heat stress. The present study was conducted in order to evaluate the efficiency of four various types of contemporary personal body cooling systems based on the ?Phase Change Material? (PCM), and its effects on soldiers? subjective comfort and physiological performance during exertional heat stress in hot environments. Methods. Ten male soldiers were voluntarily subjected to exertional heat stress tests (EHSTs) consisted of walking on a treadmill (5.5 km/h) in hot conditions (40?C) in climatic chamber, wearing NBC isolating impermeable protective suits. One of the tests was performed without any additional cooling solution (NOCOOL), and four tests were performed while using different types of cooling systems: three in a form of vests and one as underwear. Physiological strain was determined by the mean skin temperature (Tsk), tympanic temperature (Tty), and heart rate values (HR), while sweat rates (SwR) indicated changes in hydration status. Results. In all the cases EHST induced physiological response manifested through increasing Tty, HR and SwR. Compared to NOCOOL tests, when using cooling vests, Tty and Tsk were significantly lower (on 35th min, for 0.44 ? 0.03 and 0.49 ? 0.05?C, respectively; p < 0.05), as well as the average SwR (0.17 ? 0.03 L/m2/h). When using underwear, the values of given parameters were not significantly different compared to NOCOOL tests. Conclusions. Using a body cooling system based on PCM in the form of vest under NBC protective clothes during physical activity in hot conditions, reduces sweating and alleviates heat stress manifested by increased core and skin temperatures and heart rate values. These effects directly improve heat tolerance, hydration state, decrease in the risk of heat illness, and extends the duration of soldiers? exposure to extreme conditions.

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Laitano, Orlando, Lisa R. Leon, William O. Roberts, and Michael N. Sawka. "Controversies in exertional heat stroke diagnosis, prevention, and treatment." Journal of Applied Physiology 127, no. 5 (November 1, 2019): 1338–48. http://dx.doi.org/10.1152/japplphysiol.00452.2019.

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During the past several decades, the incidence of exertional heat stroke (EHS) has increased dramatically. Despite an improved understanding of this syndrome, numerous controversies still exist within the scientific and health professions regarding diagnosis, pathophysiology, risk factors, treatment, and return to physical activity. This review examines the following eight controversies: 1) reliance on core temperature for diagnosing and assessing severity of EHS; 2) hypothalamic damage induces heat stroke and this mediates “thermoregulatory failure” during the immediate recovery period; 3) EHS is a predictable condition primarily resulting from overwhelming heat stress; 4) heat-induced endotoxemia mediates systemic inflammatory response syndrome in all EHS cases; 5) nonsteroidal anti-inflammatory drugs for EHS prevention; 6) EHS shares similar mechanisms with malignant hyperthermia; 7) cooling to a specific body core temperature during treatment for EHS; and 8) return to physical activity based on physiological responses to a single-exercise heat tolerance test. In this review, we present and discuss the origins and the evidence for each controversy and propose next steps to resolve the misconception.

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Sonna, Larry A., C. Bruce Wenger, Scott Flinn, Holly K. Sheldon, Michael N. Sawka, and Craig M. Lilly. "Exertional heat injury and gene expression changes: a DNA microarray analysis study." Journal of Applied Physiology 96, no. 5 (May 2004): 1943–53. http://dx.doi.org/10.1152/japplphysiol.00886.2003.

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This study examined gene expression changes associated with exertional heat injury (EHI) in vivo and compared these changes to in vitro heat shock responses previously reported by our laboratory. Peripheral blood mononuclear cell (PBMC) RNA was obtained from four male Marine recruits (ages 17-19 yr) who presented with symptoms consistent with EHI, core temperatures ranging from 39.3 to 42.5°C, and elevations in serum enzymes such as creatine kinase. Controls were age- and gender-matched Marines from whom samples were obtained before and several days after an intense field-training exercise in the heat (“The Crucible”). Expression analysis was performed on Affymetrix arrays (containing ∼12,600 sequences) from pooled samples obtained at three times for EHI group (at presentation, 2-3 h after cooling, and 1-2 days later) and compared with control values (average signals from two chips representing pre- and post-Crucible samples). After post hoc filtering, the analysis identified 361 transcripts that had twofold or greater increases in expression at one or more of the time points assayed and 331 transcripts that had twofold or greater decreases in expression. The affected transcripts included sequences previously shown to be heat-shock responsive in PBMCs in vitro (including both heat shock proteins and non-heat shock proteins), a number of sequences whose changes in expression had not previously been noted as a result of in vitro heat shock in PBMCs (including several interferon-induced sequences), and several nonspecific stress response genes (including ubiquitin C and dual-specificity phosphatase-1). We conclude that EHI produces a broad stress response that is detectable in PBMCs and that heat stress per se can only account for some of the observed changes in transcript expression. The molecular evidence from these patients is thus consistent with the hypothesis that EHI can result from cumulative effects of multiple adverse interacting stimuli.

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Hiss, Jehuda, Tzipi Kahana, Chen Kugel, and Yoram Epstein. "3. Fatal Classic and Exertional Heat Stroke — Report of Four Cases." Medicine, Science and the Law 34, no. 4 (October 1994): 339–43. http://dx.doi.org/10.1177/002580249403400414.

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Heat stroke is the outcome of impaired heat dissipation which is aggravated by hot and humid environmental conditions. The very young and debilitated on the one hand and healthy individuals under considerable physical stress on the other are vulnerable to heat stroke. Post-mortem findings will depend on the time lapse between the stroke event and death. We report on the deaths resulting from heat stroke in a 12-month-old baby and three 19-year-old soldiers. Reconstruction of the environmental conditions enables elucidation of the circumstances that precipitated exogenous hyperpyrexia. The Discomfort Index presents reliable criteria for the assessment of heat load: values above 28 units are considered as severe heat load and are life threatening. Awareness of the hazards related to severe heat load on the body is helpful in preventing avoidable calamities.

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Radakovic, Sonja S., Jelena Maric, Maja Surbatovic, Slavica Radjen, Elka Stefanova, Nebojsa Stankovic, and Nikola Filipovic. "Effects of Acclimation on Cognitive Performance in Soldiers during Exertional Heat Stress." Military Medicine 172, no. 2 (February 2007): 133–36. http://dx.doi.org/10.7205/milmed.172.2.133.

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McLellan, Tom M., and Heather E. Wright. "Prolactin as an Indicator of Impending Fatigue during Uncompensable Exertional Heat Stress." Medicine & Science in Sports & Exercise 42 (May 2010): 275. http://dx.doi.org/10.1249/01.mss.0000384365.82918.32.

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Flouris, Andreas D., Heather E. Wright-Beatty, Brian J. Friesen, Douglas J. Casa, and Glen P. Kenny. "Treatment of exertional heat stress developed during low or moderate physical work." European Journal of Applied Physiology 114, no. 12 (August 15, 2014): 2551–60. http://dx.doi.org/10.1007/s00421-014-2971-1.

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Otani, Hidenori, Takayuki Goto, Yuki Kobayashi, Minayuki Shirato, Heita Goto, Yuri Hosokawa, Ken Tokizawa, and Mitsuharu Kaya. "Greater thermoregulatory strain in the morning than late afternoon during judo training in the heat of summer." PLOS ONE 15, no. 12 (December 1, 2020): e0242916. http://dx.doi.org/10.1371/journal.pone.0242916.

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Purpose The time-of-day variations in environmental heat stress have been known to affect thermoregulatory responses and the risk of exertional heat-related illness during outdoor exercise in the heat. However, such effect and risk are still needed to be examined during indoor sports/exercises. The current study investigated the diurnal relationships between thermoregulatory strain and environmental heat stress during regular judo training in a judo training facility without air conditioning on a clear day in the heat of summer. Methods Eight male high school judokas completed two 2.5-h indoor judo training sessions. The sessions were commenced at 09:00 h (AM) and 16:00 h (PM) on separate days. Results During the sessions, indoor and outdoor heat stress progressively increased in AM but decreased in PM, and indoor heat stress was less in AM than PM (mean ambient temperature: AM 32.7±0.4°C; PM 34.4±1.0°C, P<0.01). Mean skin temperature was higher in AM than PM (P<0.05), despite greater dry and evaporative heat losses in AM than PM (P<0.001). Infrared tympanic temperature, heart rate and thermal sensation demonstrated a trial by time interaction (P<0.001) with no differences at any time point between trials, showing relatively higher responses in these variables in PM compared to AM during the early stages of training and in AM compared to PM during the later stages of training. There were no differences between trials in body mass loss and rating of perceived exertion. Conclusions This study indicates a greater thermoregulatory strain in the morning from 09:00 h than the late afternoon from 16:00 h during 2.5-h regular judo training in no air conditioning facility on a clear day in the heat of summer. This observation is associated with a progressive increase in indoor and outdoor heat stress in the morning, despite a less indoor heat stress in the morning than the afternoon.

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KAY, MARK A., and EDWARD D. B. MCCABE. "Escherichia coli Sepsis and Prolonged Hypophosphatemia Following Exertional Heat Stroke." Pediatrics 86, no. 2 (August 1, 1990): 307–9. http://dx.doi.org/10.1542/peds.86.2.307.

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Because of the increasing emphasis on physical activity, sports medicine represents a growing proportion of medical care. Climatic heat stress, including heat stroke, is of sufficient concern that its preventability has been addressed by the American Academy of Pediatrics.1 Although heat stroke is defined by the triad of hyperpyrexia, anhydrosis, and altered mental status, the clinical course of these patients may include multiple complications.2-8 In this article we describe a previously unrecognized etiologic relationship between two of these complications, which may permit early identification and prevention of life-threatening consequences to heat stroke. Two cases of Gram-negative sepsis have been described in previously healthy young adults suffering from fatal exertional heat stroke.7,8

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Low, Ivan C. C., X. R. Tan, Mary C. Stephenson, T. W. Soong, and Jason K. W. Lee. "Functional Changes in Motor Cortical Brain Regions following Passive and Exertional Heat Stress." Medicine & Science in Sports & Exercise 49, no. 5S (May 2017): 452. http://dx.doi.org/10.1249/01.mss.0000518126.47918.66.

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Garcia, Christian K., Alex J. Mattingly, Gerard P. Robinson, Orlando Laitano, Michelle A. King, Shauna M. Dineen, Lisa R. Leon, and Thomas L. Clanton. "Sex-dependent responses to exertional heat stroke in mice." Journal of Applied Physiology 125, no. 3 (September 1, 2018): 841–49. http://dx.doi.org/10.1152/japplphysiol.00220.2018.

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With increasing participation of females in endurance athletics and active military service, it is important to determine if there are inherent sex-dependent susceptibilities to exertional heat injury or heat stroke. In this study we compared responses of male and female adult mice to exertional heat stroke (EHS). All mice were instrumented for telemetry core temperature measurements and were exercise-trained for 3 wk before EHS. During EHS, environmental temperature was 37.5°C (35% RH) while the mice ran on a forced running wheel, using incremental increases in speed. The symptom-limited endpoint was loss of consciousness, occurring at ~42.2°C core temperature. Females ran greater distances (623 vs. 346 m, P < 0.0001), reached faster running speeds (7.2 vs. 5.1 m/min, P < 0.0001), exercised for longer times (177 vs. 124 min, P < 0.0001), and were exposed to greater internal heat loads (240 vs.160°C·min; P < 0.0001). Minimum Tc during hypothermic recovery was ~32.0°C in both sexes. Females lost 9.2% body weight vs. 7.5% in males ( P < 0.001). Females demonstrated higher circulating corticosterone (286 vs 183 ng/ml, P = 0.001, at 3 h), but most plasma cytokines were not different. A component of performance in females could be attributed to greater body surface area/mass and greater external power performance. However, there were significant and independent effects of sex alone and a crossed effect of “sex × power” on performance. These results demonstrate that female mice have greater resistance to EHS during exercise in hyperthermia and that these effects cannot be attributed solely to body size. NEW & NOTEWORTHY Female mice are surprisingly more resistant to exertional heat stroke than male mice. They run faster and longer and can withstand greater internal heat loads. These changes cannot be fully accounted for by increased body surface/mass ratio in females or on differences in aerobic performance. Although the stress-immune response in males and females was similar, females exhibited markedly higher plasma corticosteroid levels, which were sustained over 14 days of recovery.

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DuBose, David A., C. Bruce Wenger, Scott D. Flinn, Thomas A. Judy, Alexandre I. Dubovtsev, and David H. Morehouse. "Distribution and mitogen response of peripheral blood lymphocytes after exertional heat injury." Journal of Applied Physiology 95, no. 6 (December 2003): 2381–89. http://dx.doi.org/10.1152/japplphysiol.00039.2003.

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To determine whether immune disturbances during exertional heat injury (EHI) could be distinguished from those due to exercise (E), peripheral lymphocyte subset distributions and phytohemagglutinin-stimulated CD69 mitogen responses as discriminated by flow cytometry were studied in military recruits [18.7 ± 0.3 (SE) yr old] training in warm weather. An E group (3 men and 3 women) ran 1.75–2 miles. During similar E, 11 recruits (10 men and 1 woman) presented with suspected EHI. EHI (40.4 ± 0.3°C) vs. E (38.6 ± 0.2°C) body temperature was significantly elevated ( P < 0.05). Heat illness was largely classified as EHI, not heatstroke, because central nervous system manifestations were generally mild. Blood was collected at E completion or EHI onset (0 h) and 2 and 24 h later. At 0 h (EHI vs. E), suppressor, natural killer, and total lymphocyte counts were significantly elevated, helper and B lymphocyte counts remained similar, and the helper-to-suppressor ratio was significantly depressed. By 2 h, immune cell dynamics between groups were similar. From 0 to 24 h, T lymphocyte subsets revealed significantly reduced phytohemagglutinin responses (percent CD69 and mean CD69 fluorescent intensity) in EHI vs. E. Thus immune cell dynamics with EHI were distinguishable from E. Because heat stress as reported in exercise or heatstroke is associated with similar immune cell disturbances, these findings in EHI contributed to the suggestion that heat stress of varying severity shares a common pathophysiological process influencing the immune system.

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Grundstein, Andrew J., Yuri Hosokawa, and Douglas J. Casa. "Fatal Exertional Heat Stroke and American Football Players: The Need for Regional Heat-Safety Guidelines." Journal of Athletic Training 53, no. 1 (January 1, 2018): 43–50. http://dx.doi.org/10.4085/1062-6050-445-16.

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Context: Weather-based activity modification in athletics is an important way to minimize heat illnesses. However, many commonly used heat-safety guidelines include a uniform set of heat-stress thresholds that do not account for geographic differences in acclimatization. Objective: To determine if heat-related fatalities among American football players occurred on days with unusually stressful weather conditions based on the local climate and to assess the need for regional heat-safety guidelines. Design: Cross-sectional study. Setting: Data from incidents of fatal exertional heat stroke (EHS) in American football players were obtained from the National Center for Catastrophic Sport Injury Research and the Korey Stringer Institute. Patients or Other Participants: Sixty-one American football players at all levels of competition with fatal EHSs from 1980 to 2014. Main Outcome Measure(s): We used the wet bulb globe temperature (WBGT) and a z-score WBGT standardized to local climate conditions from 1991 to 2010 to assess the absolute and relative magnitudes of heat stress, respectively. Results: We observed a poleward decrease in exposure WBGTs during fatal EHSs. In milder climates, 80% of cases occurred at above-average WBGTs, and 50% occurred at WBGTs greater than 1 standard deviation from the long-term mean; however, in hotter climates, half of the cases occurred at near average or below average WBGTs. Conclusions: The combination of lower exposure WBGTs and frequent extreme climatic values in milder climates during fatal EHSs indicates the need for regional activity-modification guidelines with lower, climatically appropriate weather-based thresholds. Established activity-modification guidelines, such as those from the American College of Sports Medicine, work well in the hotter climates, such as the southern United States, where hot and humid weather conditions are common.

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Gaskell, Stephanie K., Bonnie Taylor, Jane Muir, and Ricardo J. S. Costa. "Impact of 24-h high and low fermentable oligo-, di-, monosaccharide, and polyol diets on markers of exercise-induced gastrointestinal syndrome in response to exertional heat stress." Applied Physiology, Nutrition, and Metabolism 45, no. 6 (June 2020): 569–80. http://dx.doi.org/10.1139/apnm-2019-0187.

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The study aimed to determine the effects of 24-h high (HFOD) and low (LFOD) fermentable oligo-, di-, monosaccharide, and polyol (FODMAP) diets before exertional heat stress on gastrointestinal integrity, function, and symptoms. Eighteen endurance runners consumed a HFOD and a LFOD (double-blind crossover design) before completing 2 h of running at 60% maximal oxygen uptake in 35 °C ambient temperature. Blood samples were collected before and after exercise to determine plasma cortisol and intestinal fatty acid binding protein (I-FABP) concentrations, and bacterial endotoxin and cytokine profiles. Breath hydrogen (H2) and gastrointestinal symptoms (GIS) were determined pre-exercise, every 15 min during, and in recovery. No differences were observed for plasma cortisol concentration between diets. Plasma I-FABP concentration was lower on HFOD compared with LFOD (p = 0.033). A trend for lower lipopolysaccharide binding protein (p = 0.088), but not plasma soluble CD14 (p = 0.478) and cytokine profile (p > 0.05), responses on HFOD was observed. A greater area under the curve breath H2 concentration (p = 0.031) was observed throughout HFOD (mean and 95% confidence interval: HFOD 2525 (1452–3597) ppm·4 h−1) compared with LFOD (1505 (1031–1978) ppm·4 h−1). HFOD resulted in greater severity of GIS compared with LFOD (pre-exercise, p = 0.017; during, p = 0.035; and total, p = 0.014). A 24-h HFOD before exertional heat stress ameliorates disturbances to epithelial integrity but exacerbates carbohydrate malabsorption and GIS severity in comparison with a LFOD. Novelty Twenty-four-hour high FODMAP diet ameliorated disturbances to gastrointestinal integrity. Twenty-four-hour high FODMAP diet results in greater carbohydrate malabsorption compared with low FODMAP diet. Incidence of GIS during exertional heat stress were pronounced on both low and high FODMAP diets, but greater GIS severity was observed with high FODMAP diet.

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Jovanovic, Dalibor, Radovan Karkalic, Ljubisa Tomic, Zlate Velickovic, and Sonja Radakovic. "Efficacy of a novel phase change material for microclimate body cooling." Thermal Science 18, no. 2 (2014): 657–65. http://dx.doi.org/10.2298/tsci130216129j.

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The present study was conducted in order to evaluate the efficiency of personal body microclimate cooling systems based on a phase change materials (PCM) and its effects on physiological strain in soldiers during exertional heat stress in hot environment. The results are obtained in the experiment conducted in the climatic chamber in the Institute of Hygiene, Military Medical Academy in Belgrade. Ten male soldiers were voluntarily subjected to exertional heat stress tests (EHST) consisted of walking on treadmill (5.5 km/h) in hot conditions (40?C) in climatic chamber. The subjects performed first test while wearing a field camouflage uniform without any cooling system ("CONTROL" group) and in second test they used additional microclimate cooling system with paraffin wax consist of n-hexadecane (C16H34), in a form of cooling packs ("COOL" group). As indicators of thermal strain, mean skin (Tsk) and tympanic (Tty) temperature were determined. Simultaneously, thermal effects of PCM were measured by thermal imaging camera. The exercise in hot conditions induced a physiological response to heat stress, manifested through increased body core and skin temperatures. The results confirmed that the cooling vest worn over the field uniform was able to attenuate the physiological strain during exercise, compared to the identical exposure in the ''control'' group. The results of thermal imaging also indicate that heat generated inside the body is the main factor that will affect the phase change material melting time.

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Wright Beatty, Heather E., Jocelyn M. Keillor, Stephen G. Hardcastle, Pierre Boulay, and Glen P. Kenny. "Preservation of Cognitive Performance with Age during Exertional Heat Stress under Low and High Air Velocity." BioMed Research International 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/619103.

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Older adults may be at greater risk for occupational injuries given their reduced capacity to dissipate heat, leading to greater thermal strain and potentially cognitive decrements.Purpose.To examine the effects of age and increased air velocity, during exercise in humid heat, on information processing and attention.Methods.Nine young (24 ± 1 years) and 9 older (59 ± 1 years) males cycled 4 × 15 min (separated by 15 min rest) at a fixed rate of heat production (400 W) in humid heat (35°C, 60% relative humidity) under 0.5 (low) and 3.0 (high) m·s−1air velocity wearing coveralls. At rest, immediately following exercise (end exercise), and after the final recovery, participants performed an abbreviated paced auditory serial addition task (PASAT, 2 sec pace).Results.PASAT numbers of correct responses at end exercise were similar for young (low = 49 ± 3; high = 51 ± 3) and older (low = 46 ± 5; high = 47 ± 4) males and across air velocity conditions, and when scored relative to age norms. Psychological sweating, or an increased sweat rate with the administration of the PASAT, was observed in both age groups in the high condition.Conclusion.No significant decrements in attention and speeded information processing were observed, with age or altered air velocity, following intermittent exercise in humid heat.

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Pryor, Riana R., Jennifer R. Seitz, Julia Morley, Joe Suyama, Francis X. Guyette, Steven E. Reis, and David Hostler. "Estimating Core Temperature with External Devices After Exertional Heat Stress in Thermal Protective Clothing." Prehospital Emergency Care 16, no. 1 (January 2012): 136–41. http://dx.doi.org/10.3109/10903127.2011.614047.

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Sidman, Robert D., and E. John Gallagher. "Exertional Heat Stroke in a Young Woman: Gender Differences in Response to Thermal Stress." Academic Emergency Medicine 2, no. 4 (April 1995): 315–19. http://dx.doi.org/10.1111/j.1553-2712.1995.tb03229.x.

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Greisler, Luke D., Ben J. Lee, Tessa R. Flood, Ania M. Hiles, Mark ET Willems, Ella F. Walker, Garrett W. Hill, Phebe A. Romano, and Matthew R. Kuennen. "New Zealand Blackcurrant Extract Modulates Peripheral Blood Mononuclear Cell Response To Exertional Heat Stress." Medicine & Science in Sports & Exercise 52, no. 7S (July 2020): 970–71. http://dx.doi.org/10.1249/01.mss.0000686120.21274.d2.

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Snipe, Rhiannon, and et. al. "Can carbohydrate and protein intake prevent gut-immune perturbations induced by exertional-heat stress?" Annals of Research in Sport and Physical Activity, ex2018 (2018): 101–2. http://dx.doi.org/10.14195/2182-7087_ex2018_27.

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Périard, Julien D., Thijs M. H. Eijsvogels, and Hein A. M. Daanen. "Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies." Physiological Reviews 101, no. 4 (October 1, 2021): 1873–979. http://dx.doi.org/10.1152/physrev.00038.2020.

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A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances, and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat by examining the benefits of heat acclimation, cooling strategies, and hyperhydration. Finally, contemporary controversies are summarized and future research directions are provided.

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Selkirk, Glen A., Heather E. Wright, Shawn G. Rhind, and Tom M. McLellan. "Changes In Circulating Immuno-inflammatory Mediators Following Repeated Exertional Heat Stress Exposures In Untrained Males." Medicine & Science in Sports & Exercise 42 (May 2010): 364–65. http://dx.doi.org/10.1249/01.mss.0000384644.52609.af.

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Shephard, R. J. "Aural Canal, Esophageal, and Rectal Temperatures During Exertional Heat Stress and the Subsequent Recovery Period." Yearbook of Sports Medicine 2011 (January 2011): 303–5. http://dx.doi.org/10.1016/s0162-0908(10)79723-3.

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Journal articles on the topic 'Exertional heat stress'

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