Yuval Heled

Heller Institute of Medical Research · Sheba Medical Center Tel Hashomer, Israel

Exertional heat stroke (EHS) is a true medical emergency with potential for organ injury and death. This consensus statement emphasizes that optimal exertional heat illness management is promoted by a synchronized chain of survival that promotes rapid recognition and management, as well as communication between care teams. Health care providers sho...

Introduction Infantry recruit attrition wastes resources and can affect combat readiness. The purpose of this study was to examine the utility of preinduction tests as a predictor of attrition among conscripts in the first year of infantry training. Methods 303 infantry conscripted recruits participated in a prospective study. Before their service...

We tested whether salt preference increases immediately after exertion-induced Na⁺ loss in sweat, and whether this may generalize to an increase in habitual dietary Na⁺ intake. For the first aim, trained athletes (n=20) exercised in 2 ambient temperatures and sweat Na⁺ loss related to immediate salt preference assessed by taste, intake and psychoph...

Background Soldiers in modern armies perform tasks that are increasingly technologically dependent. Training them to obtain necessary technological skills is both complex and expensive. Personnel attrition is costly and can affect military readiness. The purpose of this study was to examine the utility of pre-induction tests as a predictor of attri...

It is well-established that physical exercise in humans improves cognitive functions, such as executive functions, pattern separation, and working memory. It is yet unknown, however, whether spatial learning, long known to be affected by exercise in rodents, is also affected in humans. In order to address this question, we recruited 20 healthy youn...

Traumatic brain injury (TBI), caused by mechanical impact to the brain, is a leading cause of death and disability among young adults, with slow and often incomplete recovery. Preemptive treatment strategies may increase the injury resilience of high-risk populations such as soldiers and athletes. In this work, the xanthophyll carotenoid Astaxanthi...

Background Athletes, soldiers, and rescue personnel must often perform intense, prolonged, and physically demanding activities while maintaining cognitive focus. As cognitive and physical functions are believed to share central nervous system resources, their simultaneous activation can cause reciprocal disruptions in the performance of both. Meth...

Background: Athletes, soldiers, and rescue personnel must often perform intense, prolonged, and physically demanding activities while maintaining cognitive focus. As cognitive and physical functions are believed to share central nervous system resources, their simultaneous activation can cause reciprocal disruptions in the performance of both. Meth...

Due to an unfortunate misunderstanding, the top part of Figures 2 and 3 are not correctly displayed. The original article has been corrected and the proper version of Figures 2 and 3 is also published here.

Astaxanthin is a powerful carotenoid antioxidant prevalent in marine organisms and approved as a food supplement. Recent studies have demonstrated Astaxanthin’s beneficial attributes in various health states. Following initial reports of potential heat protective properties in Astaxanthin supplemented rats, we present here results of a novel study...

Objectives: To examine the supplementation effects of the xanthophyll carotenoid Astaxanthin on physical performance and exertional heat strain in humans. Design: A randomized double blind placebo controlled trial. Methods: Twenty two male participants (Age: 23.14 ± 3.5 y, height: 175 ± 6 cm, body mass: 69.6 ± 8.7 kg, % body fat: 16.8 ± 3.8) receiv...

Exertional heat stroke (EHS) is a leading cause of preventable morbidity and mortality among both athletes and warfighters. Therefore, it is important to find blood biomarkers to predict susceptibility to EHS. We compared gene expression profiling from blood cells between two groups of participants - those with and those without a history EHS - by...

Purpose: Heat intolerance (HI) is determined in the Israel Defense Force according to a heat tolerance test (HTT) before returning to duty after an exertional heat stroke (EHS) event. Recently, increased numbers of female combatants resulted in an increased number of EHS cases among women and a higher percentage of heat intolerance (HI) individuals...

Background: Aerobic exercise under muscle fatigue can lead to muscular damage and injuries. Finding the correlations between central and peripheral microcirculation variables, as well as with electromyography signals of leg muscles during aerobic exercise, may contribute to early muscle fatigue identification. The goal of this study was to charact...

Exertional heat stroke (EHS) is a leading cause of preventable morbidity and mortality among both athletes and warfighters. Since current evidence suggests that the history of a prior event is an important risk factor for an EHS event, sports medicine providers can find post-EHS return to play/duty (RTP/D) decisions challenging. Heat tolerance test...

Exertional Heat Stroke (EHS) is a life-threatening illness that affects both athletic and military populations. It continues to be among one of the top three leading causes of death in these cohorts and remains largely preventable. Although clear guidelines have been established for the successful treatment of EHS, the process of returning individu...

Introduction: A loss of 1% or more of bodyweight due to dehydration has a negative effect on cognitive performance, which could critically affect flight safety. There is no mention in the literature concerning the amounts of military pilots' fluid loss during flight. The aim of this study was to quantify fluid loss of pilots during military flight...

Introduction: Prolonged and strenuous exercise may lead to changes in the immune system function and to temporary suppression in defense against pathogens. These changes likely increase the risk of those engaging in prolonged and strenuous physical activity to develop upper respiratory tract infection and to reduce the level of performance. On the...

Objectives: Heat-tolerance-testing (HTT) protocol is used as a screening test for secondary prevention of exertional heat illness (EHI) in the military. Subjects whose test results are positive (heat-intolerant, HI) are presumed to be at higher risk of repeated EHI events than heat-tolerant subjects (HT) and are therefore prevented from return to...

Introduction: Rhabdomyolysis is a syndrome characterized by muscle necrosis followed by release of intracellular muscle contents into the circulation. Exertional rhabdomyolysis (ER) occurs in response to nonfamiliar and/or excessive, prolonged, or repetitive exercises, with eccentric characteristics. In military populations, due to the type of int...

Soldiers are often required to carry loads which impose biomechanical strain on the human body. This can adversely affect physical performances. Recently, wheel-based devices (WBD) were designed to reduce the load on the soldier. In the present study, a prototype of this newly developed WBD was evaluated. Thirteen volunteers performed three exercis...

In various occupations, workers may be exposed to extreme environmental conditions and physical activities. Under these conditions the ability to follow the workers' body temperature may protect them from overheating that may lead to heat related injuries. The "Dräger" Double Sensor (DS) is a novel device for assessing body-core temperature (Tc). T...

Read full text at http://rdcu.be/j30Z A common and unfortunate cause for heat stroke-related deaths in children is entrapment in closed vehicles. The aim of this study was to analyze the pathological consequences of such grave events. Autopsy reports of all children that were brought to a national forensic medicine center after being found dead i...

Background Smoking has a thermogenic effect and is associated with low physical performance. Nevertheless, a direct, quantitative effect of acute smoking on exercise heat tolerance has not been reported. Methods Sixteen healthy young male volunteers, eight cigarette smokers, and eight non-smokers participated in the study. All subjects performed a...

The common practice in the Israel defense Forces is that exertional heat related injury patients undergo a heat tolerance test 6–8 weeks post event as part of the “return to duty” process. In the case of a positive heat tolerance test the individual is classified as heat intolerant, in some cases however, the thermoregulatory recovery may be longer...

Carrying heavy weight imposes high physiological strain on the human body, which can adversely affect physical performance. This is especially important for soldiers whose physical performance level may influence mission completion and survival. Recently, wheel-based devices (WBDs), designed to reduce the load on the soldier, have been suggested as...

Anthropometric and physiological factors place female soldiers at a disadvantage relative to male soldiers in most aspects of physical performance. Average aerobic and anaerobic fitness levels are lower in women than in men. Thus, women have a lower overall work capacity and must exert themselves more than men to achieve the same output. The lower...

An increasing number of women are serving in militaries around the world. Overuse musculoskeletal injuries (OMI) are common with military activities in both sexes but are more common in female soldiers, in part because of differences in whole body and tissue-level biomechanics. Sex-based differences in whole body biomechanics such as stride length,...

Lean body mass (LBM), strongly correlates with absolute maximal oxygen uptake (VO2max), has been shown to predict load carriage performance [1]. In contrast, fat mass is considered "dead mass" (DM) that reduces mobility and effectiveness of the carrier[2,3]. Lyons et al. proposed that the ratio LBM to DM can indicate the ability to carry loads [3]....

Cardiovascular Reserve Index (CVRI) was developed as a diagnostic method for estimating quantitatively cardiovascular performance reserve [1]. It has been also been suggested in previous studies as a predictor of cardiovascular related morbidities (e.g. shock or heart failure). We aimed to investigate the CVRI ability to distinguish between heat to...

Sleep deprivation (SD) is suggested to be associated with reduced thermo-regulatory functions. This study aimed to quantify the effect of partial (PSD) and total (TSD) 24 h SD using a standard heat tolerance test (HTT). Eleven participants underwent HTT after well-rested state, PSD and TSD. No significant physiological differences were found betwee...

Objective: With the expanding role of women into previously closed combat military occupational specialties, women will likely be exposed more to challenging and extreme conditions. Physical work or exercise in extreme environments could increase the risk for exertional heat illness (EHI) and exertional heat stroke (EHS), the most severe type of E...

Prior operational activities such as marching in diverse environments, with heavy backloads may cause early fatigue and reduce the unit’s readiness. The purpose of this preliminary study was to evaluate the effect of 10-kilometer (km) march on selected, military oriented, physiological and cognitive performances. Eight healthy young males (age 25 ±...

Exertional heat stroke (EHS) is a clinical syndrome of hyperthermia, encephalopathy and multi-organ dysfunction that can be irreversible and fatal. Prompt recognition and immediate, aggressive total body cooling can prevent progression of the clinical syndrome, but even a short delay can exacerbate the effects of hyperthermic-induced changes. EHS i...

Exertional heat stroke (EHS) is a clinical syndrome of hyperthermia, encephalopathy, and multiorgan dysfunction that can be irreversible and fatal. While prompt recognition and immediate, aggressive total body cooling can prevent progression of the clinical syndrome, even a short delay can exacerbate the effects of hyperthermia-induced changes. EHS...

This study investigated associations between heat intolerance, as determined by performance on a heat tolerance test (HTT), and anthropometric measurements (body surface-to-mass ratio, percent body fat, body mass index, and waist circumference) and cardiorespiratory fitness (maximal oxygen uptake [VO2max]). Relationships between predictive variable...

Introduction The common practice in the Israel Defense Force is that all exertional heat related injuries victims undergo a heat tolerance test (HTT) as a part of the "return to duty" process. The purpose of this study was to develop a quantitative, supportive physiological index for the assessment of the HTT based on the understanding that heat st...

Exertional rhabdomyolysis (ER) is a common medical condition encountered by primary care and sports medicine providers. Although the majority of individuals with ER follow an expected and unremarkable clinical course without any adverse long-term sequelae or increased risk for recurrence, in others, the condition can serve as an 'unmasker' of an un...

The heat tolerance test (HTT) is a standardized physiological test that constitutes one of the considerations in the Israel Defence Forces (IDF) for return to duty after a heat injury. The HTT consists of a 2 h controlled exercise-heat stress with a threshold of maximal rectal temperature (Tc) and heart rate (HR) values above which subjects are ref...

The purposes of this report are to review and discuss the issue of recurrent exertional rhabdomyolysis (ER), the return to physical activity after ER, and the possible causes of recurrence, with special consideration to metabolic myopathies and the possibility of an acquired post-ER myopathy. We discuss the medical investigation required prior to r...

Exertional rhabdomyolysis (ER) occurs in young, otherwise healthy, individuals principally during strenuous exercise, athletic, and military training. Although many risk factors have been offered, it is unclear why some individuals develop ER when participating in comparable levels of physical exertion under identical environmental conditions and o...

Abstract Cytokines are intracellular peptides that serve as immune mediators. The levels of both pro- and anti-inflammatory cytokines have been demonstrated to rise in the event of heat stroke in both human and animal models. Different hyperthermic states, including both normal exercise-induced hyperthermia and classical and exertional heat stroke,...

Exertional heat stroke (EHS) is a common clinical problem for both athletes and warriors; however, evidence-based guidance for return-to-play/duty (RTP/RTD) decisions is limited. Heat tolerance testing (HTT) has been proposed as a potential tool that, when combined with appropriate clinical information, may assist in RTP/RTD decisions. However, cur...

Objectives: The high values of thermal resistance (Rct) and/or vapor resistance (Ret) of chemical protective clothing (CPC) induce a considerable thermal stress. The present study compared the physiological strain induced by CPCs and evaluates the relative importance of the fabrics' Rct, Ret, and air permeability in determining heat strain. Metho...

Anthropometric and physiological factors place the average female soldier at a disadvantage relative to male soldiers in most aspects of physical performance. Aerobic and anaerobic fitness levels are lower in women than in men. Thus, women have a lower overall work capacity and must therefore exert themselves more than men to achieve the same outpu...

Aim: To evaluate the effect of physical activity on the structural, morphological, and metabolic characteristics of the gastrocnemius muscle in familial Mediterranean fever (FMF) patients, utilizing quantitative (31)P magnetic resonance spectroscopy (MRS), in order to elucidate the mechanism of their exertional leg pain. Materials and methods: E...

Hypoxia is known to reduce performance. Adaptation is limited and requires special conditions. Heat and hypoxia have been shown to share some adaptive mechanisms. The purpose of this study was to test the possibility that prior heat acclimation may preserve performance under hypoxia. Eight young healthy men participated in this study. They went thr...

Heat-related injuries, and specifically exertional heat stroke, are a significant occupational risk in the armed forces, especially for those soldiers who are rapidly deployed from a temperate climate region to hot climate regions. Traditionally, adaptation to heat was considered as a matter of physiological adaptation. It is clear today that these...

Appropriate and sufficient dietary intake is one of the main requirements for maintaining fitness and health. Inadequate energy intake may have a negative impact on physical performance which may result in injuries among physically active populations. The purpose of this research was to evaluate a possible relationship between dietary intake and st...

During exercise certain metabolic and physiological processes influence fluid and electrolyte balance. Fluid loss, mostly through sweating, that is not properly compensated for by drinking, may result in dehydration. Clinical manifestations of dehydration depend on the amount of fluid lost. The more severe the level of dehydration is, the greater t...

Exertional heat stroke (EHS) is the most dangerous heat-related injury. EHS may be followed by a state of heat intolerance. The Israeli Defense Forces (IDF) performs heat tolerance tests (HTT) to all heat injury victims 6-8 wk following injury as part of the "return to duty" process. The HTT protocol and normal values are based on vast experience w...

Exertional heat stroke (EHS) is the most complicated and dangerous amongst heat injuries that can lead to irreversible injury and even death. Early diagnosis and treatment are therefore crucial determinants of the patient's prognosis. The following case report depicts a soldier who presented primarily with confusion and behavioral changes during ph...

Exertional heat stroke (EHS) is a life-threatening condition, which deteriorates rapidly. Immediate cooling treatment can, therefore, be life saving. Over the past two winters, we witnessed three cases of hypothermia resulting from treatment of suspected EHS. Since no such cases were described in the literature before, we, therefore, in this study...