Walking with unilateral ankle-foot unloading: a comparative biomechanical analysis of three assistive devices.

BACKGROUND: Foot and ankle unloading is essential in various clinical contexts, including ulcers, tendon ruptures, and fractures. Choosing the right assistive device is crucial for functionality and recovery. Yet, research on the impact of devices beyond crutches, particularly ankle-foot orthoses (AFOs) designed to unload the ankle and foot, is limited. This study investigates the effects of three types of devices-forearm crutches, knee crutch, and AFO-on biomechanical, metabolic, and subjective parameters during walking with unilateral ankle-foot unloading. METHODS: Twenty healthy participants walked at a self-selected speed in four conditions: unassisted able-bodied gait, and using three unloading devices, namely forearm crutches, iWalk knee crutch, and ZeroG AFO. Comprehensive measurements, including motion capture, force plates, and metabolic system, were used to assess various spatiotemporal, kinematic, kinetic, and metabolic parameters. Additionally, participants provided subjective feedback through questionnaires. The conditions were compared using a within-subject crossover study design with repeated measures ANOVA. RESULTS: Significant differences were found between the three devices and able-bodied gait. Among the devices, ZeroG exhibited significantly faster walking speed and lower metabolic cost. For the weight-bearing leg, ZeroG exhibited the shortest stance phase, lowest braking forces, and hip and knee angles most similar to normal gait. However, ankle plantarflexion after push-off using ZeroG was most different from normal gait. IWalk and crutches caused significantly larger center-of-mass mediolateral and vertical fluctuations, respectively. Participants rated the ZeroG as the most stable, but more participants complained it caused excessive pressure and pain. Crutches were rated with the highest perceived exertion and lowest comfort, whereas no significant differences between ZeroG and iWalk were found for these parameters. CONCLUSIONS: Significant differences among the devices were identified across all measurements, aligning with previous studies for crutches and iWalk. ZeroG demonstrated favorable performance in most aspects, highlighting the potential of AFOs in enhancing gait rehabilitation when unloading is necessary. However, poor comfort and atypical sound-side ankle kinematics were evident with ZeroG. These findings can assist clinicians in making educated decisions about prescribing ankle-foot unloading devices and guide the design of improved devices that overcome the limitations of existing solutions.

[THE CLIMATE CRISIS].

INTRODUCTION: THE CLIMATE CRISIS.

Heat-Stress Preconditioning Attenuates Behavioral Responses to Psychological Stress: The Role of HSP-70 in Modulating Stress Responses.

Exposure to high ambient temperature is a stressor that influences both biological and behavioral functions and has been previously shown to have an extensive impact on brain structure and function. Physiological, cellular and behavioral responses to heat-stress (HS) (40-41 °C, 2 h) were evaluated in adult male Sprague-Dawley rats. The effect of HS exposure before predator-scent stress (PSS) exposure (i.e., HS preconditioning) was examined. Finally, a possible mechanism of HS-preconditioning to PSS was investigated. Immunohistochemical analyses of chosen cellular markers were performed in the hippocampus and in the hypothalamic paraventricular nucleus (PVN). Plasma corticosterone levels were evaluated, and the behavioral assessment included the elevated plus-maze (EPM) and the acoustic startle response (ASR) paradigms. Endogenous levels of heat shock protein (HSP)-70 were manipulated using an amino acid (L-glutamine) and a pharmacological agent (Doxazosin). A single exposure to an acute HS resulted in decreased body mass (BM), increased body temperature and increased corticosterone levels. Additionally, extensive cellular, but not behavioral changes were noted. HS-preconditioning provided behavioral resiliency to anxiety-like behavior associated with PSS, possibly through the induction of HSP-70. Targeting of HSP-70 is an attractive strategy for stress-related psychopathology treatment.

Exertional sodium loss does not increase immediate salt appetite or dietary sodium intake in athletes.

We tested whether salt preference increases immediately after exertion-induced Na+ loss in sweat, and whether this may generalise 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 psychophysical tests. For the second aim, we compared dietary and urinary Na+, and salt preference, seasoning and hedonics in the athletes and sedentary men (n = 20). No relationship was found between sodium loss during exercise and immediate preference for salt or psychophysical responses, and no differences in comparison to sedentary men. However, athlete diet had fewer foods (29.4 ± 1.5 vs 37.8 ± 1.9, p < 0.001), less seasoning (19 vs 32. p = 0.011) and more athletes reported dietary limitations (31 vs 11, p < 0.05), although nutrient content did not differ. Together these might suggest athlete adherence to a healthy diet at the expense of variety and flavour and a dissociation between dietary reports and intake. Athletes, more than controls, liked foods rich in energy and K+ suggesting compensatory-driven hedonics, although overall their intake did not differ. The findings are consistent with the absence of a salt appetite responding to Na+ loss in humans, and specifically that trained athletes do not increase their preference for salt in immediate response to exertion-induced Na+ loss and are not at risk for increased dietary Na+ compared to sedentary men.

The Cardiovascular Reserve Index-A Noninvasive Clinical Insight Into Heat Intolerance.

OBJECTIVE: To noninvasively explore the heat intolerance condition during exercise-heat stress by assessing cardiovascular (CV) performance. DESIGN: Prospective study of participants undergoing a standard heat-tolerance test (HTT). SETTING: Institutional study. PARTICIPANTS: Ninety-five young males: 16 heat-intolerant (HI) and 79 heat-tolerant (HT). INTERVENTIONS: Cardiovascular performance during an HTT was estimated by heart rate (HR) and blood pressure measurements. MAIN OUTCOME MEASURES: The sensitivity of the cardiovascular reserve index (CVRI) and the dynamic heart rate reserve (dHRR) index to predict heat intolerance was compared. RESULTS: A significant difference in the CV reserve during exercise-heat stress was exhibited between the HI and the HT groups. Starting at a similar level, the reduction in the CV reserve at HTT endpoint was much greater in the HI than the HT individuals (P < 0.0001), as depicted by both the CVRI and the dHRR. This result indicates a greater utilization of the CV reserve by HI individuals. The CVRI is likely to be better predictor of heat intolerance than the dHRR because the partial area under the curve in the high sensitivity (>90%) region of its receiver operating characteristic curve is higher (93.2 vs 76.8). CONCLUSIONS: More than being a predictor, the CVRI may provide a new clinical insight into heat intolerance because it noninvasively characterizes the efficiency of an individual's thermoregulatory mechanism and hints that an impaired CV reserve might underlie heat intolerance. The CVRI provides a noninvasive measurement of thermoregulation, which has been long awaited to enable on-field studies and dynamic monitoring of heat-exposed task forces.

Assessing rectal temperature with a novel non-invasive sensor.

Athletes, soldiers, and workers who perform intense physical activities under extreme hot conditions might encounter increased physiological thermal strain. Consequently, the increase in body core temperature (Tc) might result in heat exhaustion and heatstroke. Thus, continuously following changes in Tc is of utmost importance. Recently, the Tcore sensor (Dräger, Germany), which employs a unique dual-sensor heat flux technology, became commercially available to measure Tc, in a hospital-controlled environment. This study aimed to evaluate the possibility of using the Tcore sensor to accurately monitor rectal temperature (Tre), reflecting Tc, under exercise-heat stress. Thirteen healthy young males completed the study protocol, consisting of 90 min of moderate exercise (walking on a treadmill - 5 km/h, 4% elevation) under controlled hot/dry and hot/wet climatic conditions (30 °C/60% rh, 34 °C/40% rh, and 40 °C/40% rh). Tcore sensors were placed on the forehead and the left wrist. Temperatures from both Tcore sensors were recorded continuously together with Tre using a rectal thermistor. The original algorithm used by the company to estimate Tre from the Tcore sensor was found to be inadequate under the study's conditions and new models for the forehead and the wrist measurements were developed. Nearly 150,000 measurement sets (after filtering) were used to build independent MATLAB software algorithms and test their reliability according to the cross-validation algorithm. Bland-Altman analysis was used to compare between the results obtained by the new models to Tre. The database consisted of a large Tre range (36.5-38.9 °C). The mean errors of the models were close to zero, and the mean absolute errors were 0.20 ± 0.16 °C and 0.27 ± 0.20 °C for the forehead and wrist, respectively. 95% of the measurements from the forehead model and 86% from the wrist model were within ±0.5 °C of Tre, and 78% (forehead) and 64% (wrist) were within ±0.3 °C. Root Mean Square Deviation (RMSD) values were 0.29 °C and 0.40 °C for the forehead and wrist models, respectively. The developed models show the feasibility to use the Tcore sensor for assessing Tre under exercise-heat conditions. Furthermore, the sensor was found to be adequate for use on the wrist as well, which might be more practical for use in field conditions.

[WEARING A MASK IS A PERSONAL PROTECTION AGAINST SARS-COV-2 INFECTION EVEN IN A VACCINATION-ON-BOARDING COUNTRY].

INTRODUCTION: Even with the advent of the COVID-19 vaccine, masks and social distancing are recommended as a precautionary measure to suppress SARS-CoV-2 infection and disease. In Israel, as in many other countries, despite official regulations and widespread availability and accessibility to affordable effective masks, the use of face masks is not consistent or universal. Physicians and other medical and health professionals have a vital role to play in communicating to the public about the importance of masking and encouraging people to wear face masks correctly and consistently. This review underscores the importance of masking as a protective public health mitigation measure. It describes types of face masks mainly used by the public and their effectiveness. It emphasizes the importance of identifying and addressing barriers (e.g., physical, social, economic) to encourage widespread and sustained appropriate use of masks. The article also proposes strategies to enhance masking, such as changing social norms through targeted local interventions and governmental control of mask quality and price.

Six Hours of Manual Ventilation With a Bag-Valve-Mask Device Is Feasible and Clinically Consistent.

OBJECTIVES: Manual ventilation of intubated patients is a common intervention. It requires skill as well as physical effort and is typically restricted to brief periods. Prolonged manual ventilation may be unavoidable in some scenarios, for example, extreme mass casualty incidents. The present study tested whether nurses are capable of appropriately manually ventilating patients for 6 hours. DESIGN: Volunteers performed ventilation on an electronic simulator for 6 hours while their own cardiorespiratory variables and the quality of the delivered ventilation were measured and recorded. The volunteers scored their perceived level of effort on a standard Borg Scale. SETTING: Research laboratory at the Emergency Department, Tel Aviv Medical Center. SUBJECTS: Ten nursing staff members of the Tel Aviv Sourasky Medical Center, 25-43 years old. INTERVENTIONS: Volunteers ventilated manually a lung simulator for 6 hours. MEASUREMENTS AND MAIN RESULTS: The subjects' physiologic states, including blood pressure, heart rate, respiratory rate, and oxygen saturation, showed no significant changes over time. The quality of delivered ventilation was somewhat variable, but it was stable on the average: average tidal volume ranged between 524.8 and 607.0 mL (p = 0.33). There was a slight but significant increase (7.3-10.9 L/min [p = 0.048]) in minute volume throughout the test period, reaching values consistent with mild hyperventilation. The subjects scored their perceived working effort as very light to fairly light, with a nonsignificant gradual increase in the Borg score as the study progressed. CONCLUSIONS: Manual ventilation of intubated patients can be performed continuously for 6 hours without excessive physical effort on the part of the operator. The quality of delivered ventilation was clinically adequate for all of them. There was a mild but significant trend toward hyperventilation, albeit within safe clinical levels, which was due to an increasing ventilatory rate rather than an increase in tidal volume.

A novel body circumferences-based estimation of percentage body fat.

Anthropometric measures of body composition are often used for rapid and cost-effective estimation of percentage body fat (%BF) in field research, serial measurements and screening. Our aim was to develop a validated estimate of %BF for the general population, based on simple body circumferences measures. The study cohort consisted of two consecutive samples of health club members, designated as 'development' (n 476, 61 % men, 39 % women) and 'validation' (n 224, 50 % men, 50 % women) groups. All subjects underwent anthropometric measurements as part of their registration to a health club. Dual-energy X-ray absorptiometry (DEXA) scan was used as the 'gold standard' estimate of %BF. Linear regressions where used to construct the predictive equation (%BFcal). Bland-Altman statistics, Lin concordance coefficients and percentage of subjects falling within 5 % of %BF estimate by DEXA were used to evaluate accuracy and precision of the equation. The variance inflation factor was used to check multicollinearity. Two distinct equations were developed for men and women: %BFcal (men)=10·1-0·239H+0·8A-0·5N; %BFcal (women)=19·2-0·239H+0·8A-0·5N (H, height; A, abdomen; N, neck, all in cm). Bland-Altman differences were randomly distributed and showed no fixed bias. Lin concordance coefficients of %BFcal were 0·89 in men and 0·86 in women. About 79·5 % of %BF predictions in both sexes were within ±5 % of the DEXA value. The Durnin-Womersley skinfolds equation was less accurate in our study group for prediction of %BF than %BFcal. We conclude that %BFcal offers the advantage of obtaining a reliable estimate of %BF from simple measurements that require no sophisticated tools and only a minimal prior training and experience.

[PRINCIPLES FOR THE INTERPRETATION OF CARDIOPULMONARY EXERCISE TESTS (CPET)].

INTRODUCTION: The cardiopulmonary exercise test (CPET) permits the most accurate and reproducible quantification of cardiopulmonary fitness, a grading of the etiology and severity of cardiopulmonary impairments, and an objective assessment of the response to an intervention. Moreover, over the last three decades, a large volume of research has been directed toward the utility of CPET as a diagnostic and prognostic tool; these studies have established CPET as a scientifically sound and, therefore, clinically valuable method for accurately assessing exercise limitation and prognosis in various disease states. The CPET is relatively easy to perform, yet complex in the interpretation of the results. The current review presents the principles of the analytic process of the test results, in order to obtain possible diagnoses.

Measuring core body temperature with a non-invasive sensor.

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). The purpose of this study was to evaluate the accuracy of the DS in measuring Tc under heat stress. Seventeen male participants performed a three stage protocol: 30min rest in a thermal comfort environment (20-22°C, 50% relative humidity), followed by an exposure to a hot environment of 40°C, 40% relative humidity -30min at rest and 60min of exercise (walking on a treadmill at 5km/h and 2% elevation). Simultaneously temperatures measured by the DS (TDS) and by rectal temperature (Tre) (YSI-401 thermistor) were recorded and then compared. During the three stages of the study the average temperature obtained by the DS was within±0.3°C of rectal measurement. The correlation between TDS and Tre was significantly better during the heat exposures phases than during resting under comfort conditions. These preliminary results are promising for potential use of the DS by workers under field conditions and especially under environmental heat stress or when dressed in protective garments. For this goal, further investigations are required to validate the accuracy of the DS under various levels of heat stress, clothing and working levels.

Fatal heat stroke in children found in parked cars: autopsy findings.

UNLABELLED: 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 in closed vehicles over a 21-year period (1995-2015) were reviewed. Data extracted were the circumstances of the events, child age, sex, height and weight, time, date and duration of entrapment, and environmental temperatures at the time of entrapment and the autopsy findings. Eight deceased children were brought to the forensic medicine center for autopsy, and seven families consented to the procedure. Autopsy findings included diffuse petechiae and hemorrhages of serosal membranes (n = 7/7) and lung congestion (n = 3/7). CONCLUSION: Typical autopsy findings following classical heat stroke in children include diffuse petechiae and hemorrhages and lung involvement. These findings are similar to those reported in adults that had died following exertional heat stroke-a very different mechanism of heat accumulation. Prevention of future events can possibly be obtained by public education on the rapid heating of closed vehicles, the vulnerability of children to heat, and the caregiver role in child entrapment. WHAT IS KNOWN: • A common and unfortunate cause for heat stroke-related deaths in children is entrapment in closed vehicles. The pathological consequences of such grave events have not been previously reported. What is New: • This study is the first to describe autopsy findings from children who were found dead in parked cars. • Autopsy findings included diffuse petechiae hemorrhages of serosal membranes and lung congestion. • These findings are identical to those seen in adults following exertional heat stroke.

Physiological and Medical Aspects That Put Women Soldiers at Increased Risk for Overuse Injuries.

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 weight and fat-free mass and the higher body fat of women are associated with lower muscle strength and endurance, placing them at a disadvantage compared with men in performing military tasks such as lifting and carrying weights, or marching with a load. Working at a higher percentage of their maximal capacity to achieve the same performance levels as men, women tire earlier. Their smaller size, skeletal anatomy, and different bone geometry also predispose women to a higher incidence of exercise-related injuries. Consequently, the attrition rate of female soldiers in combat units is higher than that of their male counterparts. This review summarizes the literature on gender-related physiological and anatomical differences that put female soldiers at an increased risk of exercise-related injuries.

Deformations in the Shoulder Tissues During Load Carriage: A Computational Model.

Shoulder soft tissue deformations seem to be one of the limiting factors of load carriage among soldiers and recreational backpackers that are required to carry heavy loads. Yet, there are no loading limits related to the forces borne by the shoulders, and the backpacks designs are not consistent with providing pressure relief from this sensitive anatomical region. The aim of this study was to develop a model that will enable to study the biomechanical loads that develop in the shoulder under heavy loads and to help in optimizing load carriage systems design. A 3-dimensional, anatomically accurate finite element model of a human shoulder was constructed based on MRI scans. The model was developed to calculate the effective stresses on the skin below the shoulder strap (superficial loads) and the effective strain in the brachial plexus region (inner tissue deformation) for loads of up to 35 kg. The model successfully predicted deformations in the soft tissue surrounding the brachial plexus when compared with deformations measured from load-bearing MRI scans. The model yielded a skin pressure mapping, which showed pressure hotspots in the clavicle region. Inner tissue deformations mapping, as assessed by brachial plexus envelop strains, were found to peak at 30% effective strain at the lateral aspect below the pectoralis muscle. The newly developed model successfully predicted soft tissue deformations in the shoulder related to backpacks. This model can be used to optimize load carriage systems for better distribution of pressure over the shoulders and lower inner tissue deformations.

Sepsis, septic shock, and fatal exertional heat stroke.

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 is linked to an inflammatory response that is akin to the systemic inflammatory response syndrome (SIRS). However because EHS is not a common problem in most hospital intensive care units and is not in the usual list of SIRS causes, it may be overlooked easily. Furthermore normalizing the body temperature of patients with EHS, especially when hyperthermia recognition and total body cooling are delayed, may not prevent SIRS and its clinical consequences. This narrative review focuses on the inflammatory response behind the pathway leading to EHS-associated organ pathology and recommends a new insight to possible clinical interventions beyond whole body cooling.

[Exertional heat stroke].

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 is linked to an inflammatory response that is akin to the systemic inflammatory response syndrome (SIRS). However, because EHS is not a common problem in most hospital intensive care units and is not in the usual list of SIRS causes, it may easily be overlooked. The present case report will highlight the preliminary clinical manifestations of the syndrome, the initial optimal treatment, and its clinical sequelae.

The Significance of Body Surface Area to Mass Ratio for Thermal Responses to a Standardized Exercise-Heat Stress Test.

PURPOSE: To evaluate the significance of body surface area-to-mass ratio (BSA/mass) on the heat-tolerance test (HTT) results. We hypothesized that individuals defined as heat tolerant (HT) would have on average higher BSA/mass compared to heat intolerant (HI) individuals. METHODS: A retrospective reanalysis of the HTT results of 517 soldiers (age: 18-38 yrs., M/F: 96/4%), who were tested by the Israel Defense Forces (IDF) HTT protocol. The criterion for heat tolerance in the current analysis was a rectal temperature (Tre) plateau during the second hour of the test. A logistic regression analysis to evaluate the predictive power of BSA/mass for heat intolerance was performed; the spline model was applied to show the odds for heat intolerance across BSA/mass. RESULTS: In men BSA/mass of HI individuals was lower than HT individuals (248 ± 19 vs. 262 ± 18 cm2/kg, p < 0.01, d = 0.76). In women a similar trend was noted but with no statistical significance between HT and HI groups. The odd ratio for heat intolerance for every unit increase in BSA/mass was 0.97 (CI 95% 0.95-0.99). The spline model plateaued above BSA/mass of 270 cm2/kg. CONCLUSIONS: The results imply that body-core temperature responses to a standard exercise-heat stress (fixed external work rate and climatic conditions) are influenced by BSA/mass. More specifically, lack of a steady state in Tre (indicating heat intolerance) was more likely to occur with every unit decrease in BSA/mass. These findings contribute to a better understanding of the role of body anthropometry in the response to a standard exercise-heat task that might have an implication on clinical decision-making about return to duty/play of soldiers, athletes and others who deemed to be identified as HI.