Exertional Hyperthermia Research Articles

Skeletal Muscle Physiology

In the beginning of the last century, muscle proteins were viewed as static structural molecules not capable of being utilized by other tissues or organs. This concept was accepted until the 30s, where Rudolf Schoenheimer presented strong evidences about the “Dynamic State of Body Constituents,” which means that skeletal muscle is not only capable of contracting but also capable of releasing nitrogen derived molecules to be utilized by other organs and tissues (Guggenheim, 1991) [1]. Such concept established that skeletal muscle is a highly plastic tissue, adapting its structure and metabolism in response to diverse conditions such as contractile activity, mechanical overload, and nutrients. From this point of view several questions arise, specifically, how form follows function of skeletal muscles, as well as the synergistic role of nutrients. A large number of research groups around the world are helping to clarify this and many other questions. In particular in the last four decades, the growth in the number of publications on skeletal muscle subject is noteworthy (Figure 1). Figure 1 Number of publications in Medline database with “skeletal muscle” present on title. Data from the US National Library of Medicine National Institutes of Health (http://www.ncbi.nlm.nih.gov/pubmed?term=skeletal%20muscle [Title]). ... In this special issue, the reader will be brought directly to a wide spectrum of articles regarding the skeletal muscle tissue. From France, a new hypothesis concerning how to consume amino acids and deal with catabolic conditions also is put in debate, focusing on the anabolic threshold concept (D. Dardevet et al., 2012). From the University of Tokyo, Japan, A. Wagatsuma and K. Sakuma (2013) summarize the current knowledge about the role of mitochondria as a regulator of myogenesis. From Brazil, C. O. Assumpcao et al. (2013) present an extensive review on the effects of exercise-induced muscle damage on running economy in humans. Also, W. S. Dantas et al. (2013) discuss the impact of polycystic ovary syndrome on skeletal muscle tissue. A. Carsana (2013), from Italy, reviewed the documented cases of exertional rhabdomyolysis or stress-induced malignant hyperthermia and reported a possible association with RYR1 gene polymorphism. This special issue also presents original articles focusing on the cytokine response of skeletal muscle cells according its differentiation stage (M. Podbregar et al., 2013), the effects of tissue culture conditions on in vitro myogenesis (S. Hinds et al., 2013) and the differences in spontaneous physical activity between mice substrains (D. Coletti et al., 2013). All these discussions are being provided in order to generate new benefits and from athletes to debilitated populations; from basic to applied sciences. In this issue, our focus was not to restrict but, on the contrary, to be capable of proposing new hypotheses and ideas based on the current knowledge.

Hypohidrotic ectodermal dysplasia and physical exercise

Because of their lack of sweat glands, individuals with hypohidrotic ectodermal dysplasia (HED) are assumed to be at risk of severe hyperthermia during exercise in a warm environment. If pediatric HED patients ask whether they may practice competitive sports, most physicians are hesitant to give recommendations other than swimming, which is unlikely to lead to life-threatening exertional overheating. To study the effects of physical exercise on HED patients more systematically and to determine levels of activity they tolerate and may engage in without health hazards, 13 boys and male adolescents with X-linked HED as well as age-matched healthy male controls were investigated during standardized exercise on a bicycle ergometer at ambient temperatures of 25°C and 30°C. Protective effects of evaporative skin cooling devices were evaluated at 30°C. Body core temperature during and after exercise, heart rate, performance, endurance, and serum lactate were analyzed. HED subjects experienced a significantly greater rise in body temperature after cycling than healthy controls, and their body temperature remained elevated longer. Maximum heart rates and lactate values did not differ significantly between HED and control groups. Application of skin cooling devices led to a clinically relevant attenuation of exertional hyperthermia in HED patients, and a previous tendency towards lower performance disappeared. This first systematic study of the effects of physical exercise on HED patients demonstrated a rapid and lasting body temperature increase in HED subjects after cycling, posing them at risk of exercise-induced hyperthermia and heat-related illnesses. External evaporative skin cooling attenuates exertional overheating in HED patients and may facilitate their participation in athletic activities and professional life.

Systematic Evaluation of Exertional Hyperthermia in Children and Adolescents With Hypohidrotic Ectodermal Dysplasia: An Observational Study

To evaluate exertional overheating and the impact of physical exercise on individuals with hypohidrotic ectodermal dysplasia (HED) and to assess protective effects of cooling devices, 13 boys and male adolescents with X-linked HED (XLHED) and age-matched healthy male controls were studied during standardized exercise on a bicycle ergometer at ambient temperatures of 25 and 30°C, without cooling and with evaporative skin cooling devices at 30°C. Body core temperature during and after exercise, heart rate, performance, endurance, and serum lactate were investigated. XLHED subjects experienced a significantly greater rise in body temperature after cycling than healthy controls, and their body temperature remained elevated longer. Maximum heart rates and lactate values did not differ significantly between XLHED and control groups. Application of skin cooling devices led to a clinically relevant attenuation of exertional hyperthermia in XLHED patients, and a previous tendency toward lower performance disappeared. This first systematic study of the effects of physical exercise on HED patients demonstrates a rapid and lasting body temperature increase in XLHED subjects after cycling, posing them at risk of exercise-induced hyperthermia. External evaporative skin cooling attenuates exertional overheating in HED patients and may facilitate their participation in athletic activities and professional life.

Immersion Treatment for Exertional Hyperthermia

Immersion Treatment for Exertional Hyperthermia

Predictors Of High Body Core Temperatures During A Competitive Running Event

Exercise is associated with an increase in body core temperature (Tcore). However, little is known about factors that contribute to the exercise-induced increase in Tcore or predict the upper range of the body core temperature, often referred to as exertional hyperthermia (Tcore >40°C), during a competitive event. PURPOSE: The purpose of this study was to identify factors (personal and exercise-related) that predict the Tcore immediately after a competitive 15-km run, but also predict the presence of a Tcore >40°C (i.e. exertional hyperthermia). METHODS: Tcore, race characteristics, anthropometrical data, body mass changes and fluid intake were collected in a large heterogeneous group (n=230, 45±11 years, 49% male) who participated in a 15-km run. In addition, we performed additional analysis in urine (specific gravity) and blood samples (sodium levels) in subjects with Tcore >40°C (i.e. exertional hyperthermia) and gender- and finish time-matched peers. RESULTS: Baseline Tcore (37.6°C) increased to 37.8°C after warming-up, while it was increased further to 39.2°C at the finish. A backward linear regression model identified BMI, baseline Tcore, the individual Tcore increase during warm-up (start Tcore - baseline Tcore), and fluid intake before and during the race to significantly predict the finish Tcore (overall R2=0.25, P<0.001). After finishing, 15% of our participants (n=31) demonstrated a Tcore >40°C (i.e. exertional hyperthermia). Binary logistic regression analysis showed that only Tcore increase during warm-up was predictive for exertional hyperthermia (R2=0.16). All other characteristics, including additional blood and urine parameters, did not differ between subjects with and without exertional hyperthermia. CONCLUSION: Finish Tcore was significantly related to a number of factors (BMI, baseline Tcore, Tcore increase during warm-up, fluid intake). Nonetheless, only the individual Tcore increase during warm-up partially predicts the presence of a Tcore >40.0°C during exercise.

Absence of Exertional Hyperthermia in a 17-Year-Old Boy With Severe Burns

An important safety concern when exercising burned patients is the potential for an excessive increase in core body temperature (hyperthermia=body core temperature>39 degrees C) during exercise. We examined the thermoregulatory response to exercise in the heat (31 degrees C, relative humidity 40%) in a 17-year-old boy with a 99% TBSA burn. A 30-minute exercise test was performed at an intensity of 75% of his peak aerobic capacity. Intestinal temperature was assessed via telemetry with an ingestible capsule. Intestinal temperature was measured before, during, and postexercise. The patient completed 12 minutes of the 30-minute exercise test. Starting core temperature was 36.98 degrees C and increased 0.69 degrees C during exercise. After exercise, intestinal temperature continued to increase, but no hyperthermia was noted. It has been reported that burned children can safely exercise at room temperature; however, the response in the heat is unknown. This patient did not develop exertional hyperthermia, which we propose is due to his low-fitness level and heat intolerance. However, the potential for hyperthermia would be increased if he was forced to maintain a high relative workload in the heat. We propose that severely burned individuals should be able to safely participate in physical activities. However, the decision to stop exercising should be accepted to avoid development of exertional hyperthermia.

Acute Whole-Body Cooling for Exercise-Induced Hyperthermia: A Systematic Review

To assess existing original research addressing the efficiency of whole-body cooling modalities in the treatment of exertional hyperthermia. During April 2007, we searched MEDLINE, EMBASE, Scopus, SportDiscus, CINAHL, and Cochrane Reviews databases as well as ProQuest for theses and dissertations to identify research studies evaluating whole-body cooling treatments without limits. Key words were cooling, cryotherapy, water immersion, cold-water immersion, ice-water immersion, icing, fanning, bath, baths, cooling modality, heat illness, heat illnesses, exertional heatstroke, exertional heat stroke, heat exhaustion, hyperthermia, hyperthermic, hyperpyrexia, exercise, exertion, running, football, military, runners, marathoner, physical activity, marathoning, soccer, and tennis. Two independent reviewers graded each study on the Physiotherapy Evidence Database (PEDro) scale. Seven of 89 research articles met all inclusion criteria and a minimum score of 4 out of 10 on the PEDro scale. After an extensive and critical review of the available research on whole-body cooling for the treatment of exertional hyperthermia, we concluded that ice-water immersion provides the most efficient cooling. Further research comparing whole-body cooling modalities is needed to identify other acceptable means. When ice-water immersion is not possible, continual dousing with water combined with fanning the patient is an alternative method until more advanced cooling means can be used. Until future investigators identify other acceptable whole-body cooling modalities for exercise-induced hyperthermia, ice-water immersion and cold-water immersion are the methods proven to have the fastest cooling rates.

Cytokine induction during exertional hyperthermia is abolished by core temperature clamping: neuroendocrine regulatory mechanisms

The immunomodulatory effects of physiological temperature change remain poorly understood and inter-relationships between changes in core temperature, stress hormones and cytokines during exertional hyperthermia are not well established. This experimental study was designed to examine how cytokine (tumour necrosis factor (TNF)-α, interleukin (IL)-6, IL-12 and IL-1ra (receptor antagonist)) and hormone (epinephrine (Epi), norepinephrine (NE), growth hormone (GH) and cortisol (CORT)) responses are modified when the exercise-induced rise in core temperature is attenuated or exacerbated by immersion in a water bath. Ten men ((mean ± SD) age: 26.9 ± 5.7 years; height 1.75 ± 0.07 m; body mass 76.0 ± 10.9 kg; O2 peak: 48.0 ± 12.4 mL kg−1 min−1) completed two 40-min cycle ergometer exercise trials at 65% O2 peak while immersed to mid-chest. Rectal temperature (Tre) peaked at 39.1 ± 0.03 and 37.5 ± 0.13°C during the hot (39°C) and cold (18°C) conditions, respectively. Blood samples were collected before, during (20- and 40-min) and after (30- and 120-min) exercise. Increases in circulating NE (>350%), Epi (>500%), GH (>900%), IL-12 (>150%) and TNF-α (>90%) were greatest after 40-min exercise in the heat. Substantial elevations of CORT (80%), IL-1ra (150%) and IL-6 (>400%) did not occur until after exercise was complete. Core temperature clamping decreased the rise in circulating stress hormone concentrations and abolished increases in plasma cytokine concentrations. These findings suggest that exercise-associated elevations of Tre mediate increases of circulating stress hormones, which subsequently contribute to induction of circulating cytokine release.

Another Look at Sudden Death and Exertional Hyperthermia

Another Look at Sudden Death and Exertional Hyperthermia

FINISH LINE FATIGUE IN TRIATHLON - AN EXERCISE IN DIFFERENTIALS

1729 HISTORY - LF, a 30 yo WF high level triathlete, presented to the finish line of an Olympic Distance Championship Triathlon disoriented and unable to ambulate further without assistance. She was immediately supported, but after several steps was unable to ambulate further. She was subsequently carried immediately to the finish line medical tent. Ambient Weather: Wet Bulb Globe Temperature 81 F.; Sunny skies with haze; minimal breeze. PHYSICAL EXAMINATION: Temp. (rectal) Deferred (agitation). HR: 150. R: 30, deep. BP 110/60. Skin was warm and moist (sweaty); Turgor: Fair. MS: Awake, confused, agitated; Oriented to person, season, month; Monosyllabic. Exercise Associated Collapse Exertional Hyperthermia Dehydration INITIAL TREATMENT & FOLLOW UP: Six-point ice packs; free-flow garden hose. Two liters of normal saline given intravenously. Mental status steadily improved; HR steadily normalized. Began to take oral fluids; eventually able to ambulate unassisted. Conversation lucid and appropriate. Voided clear yellow urine. LF, a resident physician, was discharged to the care of family and friends. Subsequent to release from the Medical Tent, LF returned home, continued with dry heaves, developed frequent watery diarrhea, remained fatigued, and did not void again. She proceeded to the Emergency Room after 3 hours. Persistent Dehydration Rhabdomyolysis Acute Renal Failure / Acute Tubular Necrosis (?)Hyponatremia (?)Bowel Ischemia TEST & RESULTS IN ER: LABS: WBC = 30.45 with Left Shift; Hgb 12.9; CPK 744; Na 142, K 3.9, Cl 111, CO2 20, BUN 20, Cr 1.7; UA: Yellow, Clear, SpG 1.020, pH 5.0, Keto 15; Myoglobin - NEG. CXR: Bibasilar atelectasis/infiltrate; B/L pleural effusions. WORKING DIAGNOSIS: Dehydration; Mycoplasma pneumonia. 10-12 L NS given in ER Azithromycin LAB FOLLOW UP: Legionella: Negative. Mycoplasma: Negative (CF 1:8). Exertional Heat Injury with Dehydration & Mild Acidosis. Viral vs Other Bacterial pneumonia vs Pulmonary Congestion (Fluid Overload) Other Potential Underlying / Precipitating Process(es) • Leptospirosis; Overtraining Syndrome; Anemia vs "Sports Anemia"

ACSM Position Stand: The Female Athlete Triad: Heat and Cold Illnesses During Distance Running

Many recreational and elite runners participate in distance races each year. When these events are conducted in hot or cold conditions, the risk of environmental illness increases. However, exertional hyperthermia, hypothermia, dehydration, and other related problems may be minimized with pre-event education and preparation. This position stand provides recommendations for the medical director and other race officials in the following areas: scheduling; organizing personnel, facilities, supplies, equipment, and communication; providing competitor education; measuring environmental stress; providing fluids; and avoiding potential legal liabilities. This document also describes the predisposing conditions, recognition, and treatment of the four most common environmental illnesses: heat exhaustion, heatstroke, hypothermia, and frostbite. The objectives of this position stand are: 1) To educate distance running event officials and participants about the most common forms of environmental illness including predisposing conditions, warning signs, susceptibility, and incidence reduction. 2) To advise race officials of their legal responsibilities and potential liability with regard to event safety and injury prevention. 3) To recommend that race officials consult local weather archives and plan events at times likely to be of low environmental stress to minimize detrimental effects on participants. 4) To encourage race officials to warn participants about environmental stress on race day and its implications for heat and cold illness. 5) To inform race officials of preventive actions that may reduce debilitation and environmental illness. 6) To describe the personnel, equipment, and supplies necessary to reduce and treat cases of collapse and environmental illness.

Differential effects of exercise and heat stress on liver HSP70 accumulation with aging.

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.

Comparison between two post exercise cooling methods

SummaryForty‐two fit 3‐day‐event horses were tested under hot, humid ambient conditions to determine if application of cold water (mean 9°C) over the entire body surface after exercise would cool horses more quickly than regional application of tepid water (mean 31°C); and to determine if topical application of cold water caused myopathy. Horses were exercised under saddle for an average of 81 min. Heart rate data and post exercise plasma lactate concentrations characterised the work effort as low intensity work with short bouts of moderate intensity effort.Sixteen horses were studied in a crossover design on 2 consecutive days. Immediately after exercise, horses were randomly assigned to the hypercooling protocol (cold water on entire body surface) or the conventional protocol (tepid water on neck, shoulders, torso, underside and legs). Hypercooled horses (Group 1) had significantly lower rectal temperatures at 15, 20, 25 and 30 min after exercise compared to conventionally cooled horses (Group 2). In a supplemental study, an additional 19 horses (Group 3) were hypercooled after exercise. Mean rectal temperatures were significantly decreased from the immediate post exercise rectal temperature at 10, 15, 20 and 25 min after exercise. Based on physical examination and serum AST and CK concentrations, myopathy did not occur in any of the horses. These results suggest that application of cold water to the entire body surface relieves mild to moderate exertional hyperthermia quickly under hot, humid conditions; and that myopathy is not a common complication of this cooling approach.