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Kailin C. Parker, Rachel R. Shelton and Rebecca M. Lopez

Question Do alternative cooling methods have effective core body temperature cooling rates for hyperthermia compared with previously established CWI cooling rates? Summary of Key Findings We searched for randomized clinical trials that used alternative methods of cooling that were applied on exercising

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Timothy M. Wohlfert and Kevin C. Miller

Evidence-based Medicine (CEBM) 1 level-2 evidence or higher, with PEDro scores ≥5 Exclusion • Studies that used passive heating techniques rather than exercise to induce hyperthermia • Studies that cooled subjects during exercise (ie, percooling) • Studies that cooled subjects between exercise bouts

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Kayla E. Boehm and Kevin C. Miller

recommendations for exertional heat stroke (EHS) victims (ie, 0.15°C/min). 5 Table 1 Characteristics of Included Studies Authors Armstrong et al 3 DeMartini et al 4 Lemire et al 2 Patients, n 8000 athletes. 21 (35 [3] y) were diagnosed with extreme hyperthermia and either heat exhaustion or EHS. 17 males (age

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Robert Carter III, Samuel N. Cheuvront and Michael N. Sawka

Objectives:

We report our observations on one soldier with abnormal hyperthermia during exercise in the heat compared with prior exercise and following acute local (non-febrile) infection. Also, we report on 994 heat stroke hospitalizations in the U.S. Army. It is known that prior infection is a risk factor for heat illness and some of the 37 heat stroke deaths cited infections (eg, pneumonia, influenza) in the medical records.

Results:

This case report illustrates complete recovery from abnormal hyperthermia, which occurred in a laboratory setting during mild, low intensity exercise. In a field setting, this case may have resulted in serious heat illness. As with most of the heat stroke cases, rapid medical attention (ie, cooling and rehydration) and the age group (19 to 26) that represents majority of the heatstroke cases in U.S. Army are likely factors that contribute successful treatment of heatstroke in the field environment.

Conclusions:

We conclude that acute inflammatory response can augment the hyperthermia of exercise and possibly increase heat illness susceptibility. Furthermore, it is important for health care providers of soldiers and athletes to monitor acute local infections due to the potential thermoregulatory consequences during exercise in the heat.

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Tal Marom, David Itskoviz, Haim Lavon and Ishay Ostfeld

Introduction:

Exertional heat stroke (EHS) is a major concern in military trainees performing intense physical exercise, with substantial morbidity rates. Prehospital diagnosis of EHS is essentially clinical. Thus, soldiers, command personnel, and medical staff are taught to recognize this injury and immediately begin aggressive treatment to prevent further deterioration.

Patients and Methods:

During 2007, 5 otherwise healthy Israeli Defense Forces (IDF) soldiers were diagnosed with EHS while performing strenuous exercise. They were treated vigorously according to the IDF EHS-treatment protocol and were referred to the emergency department.

Results:

On arrival at the emergency department, physical examination including rectal temperature was unremarkable in all soldiers. Blood and urine workup showed near-normal values. No other medical conditions that could have explained the clinical presentation were found. All soldiers were discharged shortly afterward, with no further consequences. A heat-tolerance test was performed several weeks after the event and was interpreted as normal. All soldiers returned to active service.

Conclusion:

Because the initial clinical findings were very suggestive of EHS and because no other condition could have explained the prehospital transient hyperthermia, we suggest that these soldiers were correctly diagnosed with EHS, and we propose that rapid vigorous cooling prevented further deterioration and complications. We suggest calling this condition aborted heat stroke.

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Tyler T. Truxton and Kevin C. Miller

Clinical Scenario:

Exertional heat stroke (EHS) is a medical emergency which, if left untreated, can result in death. The standard of care for EHS patients includes confirmation of hyperthermia via rectal temperature (Trec) and then immediate cold-water immersion (CWI). While CWI is the fastest way to reduce Trec, it may be difficult to lower and maintain water bath temperature in the recommended ranges (1.7°C–15°C [35°F–59°F]) because of limited access to ice and/or the bath being exposed to high ambient temperatures for long periods of time. Determining if Trec cooling rates are acceptable (ie, >0.08°C/min) when significantly hyperthermic humans are immersed in temperate water (ie, ≥20°C [68°F]) has applications for how EHS patients are treated in the field.

Clinical Question:

Are Trec cooling rates acceptable (≥0.08°C/min) when significantly hyperthermic humans are immersed in temperate water?

Summary of Findings:

Trec cooling rates of hyperthermic humans immersed in temperate water (≥20°C [68°F]) ranged from 0.06°C/min to 0.19°C/min. The average Trec cooling rate for all examined studies was 0.11±0.06°C/min.

Clinical Bottom Line:

Temperature water immersion (TWI) provides acceptable (ie, >0.08°C/min) Trec cooling rates for hyperthermic humans post-exercise. However, CWI cooling rates are higher and should be used if feasible (eg, access to ice, shaded treatment areas).

Strength of Recommendation:

The majority of evidence (eg, Level 2 studies with PEDro scores ≥5) suggests TWI provides acceptable, though not ideal, Trec cooling. If possible, CWI should be used instead of TWI in EHS scenarios.

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Mitchell J. Henderson, Bryna C.R. Chrismas, Christopher J. Stevens, Aaron J. Coutts and Lee Taylor

) recovery tool for rugby sevens athletes, proposed to control hyperthermia, reduce muscle inflammation and damage, and decrease muscle soreness. 9 However, the efficacy of rugby sevens specific CWI protocols, 10 within a real-world elite tournament scenario, is not available (eg, total heat storage as a

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Column-editor : Robert I. Moss

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Jonathan P. Dugas

The regulation of temperature during exercise is a widely debated topic. Two primary views exist, with one embracing a peripheral approach and the other adopting a more integrative and central explanation of the physiology. Especially in the past 10 years, several investigators have published increasingly elegant interpretations that have moved the debate forward.

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Neil S. Maxwell, Richard W.A. Mackenzie and David Bishop

Purpose:

To examine the effect of hypohydration on physiological strain and intermittent sprint exercise performance in the heat (35.5 ± 0.6°C, 48.7 ± 3.4% relative humidity).

Methods:

Eight unacclimatized males (age 23.4 ± 6.2 y, height 1.78 ± 0.04 m, mass 76.8 ± 7.7 kg) undertook three trials, each over two days. On day 1, subjects performed 90 min of exercise/heat-induced dehydration on a cycle ergometer, before following one of three rehydration strategies. On day 2, subjects completed a 36-min cycling intermittent sprint test (IST) with a -0.62 ± 0.74% (euhydrated, EUH), -1.81 (0.99)% (hypohydrated1, HYPO1), or -3.88 ± 0.89% (hypohydrated2, HYPO2) body mass defcit.

Results:

No difference was observed in average total work (EUH, 3790 ± 556 kJ; HYPO1, 3785 ± 628 kJ; HYPO2, 3647 ± 339 kJ, P = 0.418), or average peak power (EUH, 1315 ± 129 W; HYPO1, 1304 ± 175 W; HYPO2, 1282 ± 128 W, P = 0.356) between conditions on day 2. Total work and peak power output in the sprint immediately following an intense repeated sprint bout during the IST were lower in the HYPO2 condition. Physiological strain index was greater in the HYPO2 vs. the EUH condition, but without changes in metabolic markers.

Conclusion:

A greater physiological strain was observed with the greatest degree of hypohydration; however, sprint performance only diminished in the most hypohydrated state near the end of the IST, following an intense bout of repeating sprinting.