Drowning rates among children and adolescents (aged 7-17) in Israel during the years 2008-2018.

OBJECTIVE: Drowning is one of the leading causes of death among children and youth worldwide. This study aims to examine differences in the rates of drowning (fatal and non-fatal drowning) among children and youth in Israel stratified by age, sex, sector, place of drowning, and the drowning outcome. In addition, we compared the results of studies reported in other countries in specific age groups based on statistics of about 100,000 drowning cases. METHOD: A statistical analysis of 474 drownings between 2008 and 2018 was conducted. All cases refer to youngsters aged 7-17 in the State of Israel. Statistical analysis was performed on data obtained from the Beterem - Safe Kids Israel organization and from the Israel Central Bureau of Statistics. Disparities between groups within the examined population were analyzed based on gender, sector (Jewish versus non-Jewish), and drowning site. RESULTS: Of the 474 drownings that occurred during 2008-2018, 38.4% ended in death. 79% of the cases occurred in pools. The Arab minority sector (21.1% of the general population) accounted for 25.1% of all drownings, males accounted for 70.5% of the drowning cases, and the age group with the most drownings (48.5%) was that of 15-17 years. The Jewish population was involved in more than 75% of drownings in places designated for bathing and in more than 83% of all disaster scenarios, whereas the Arab minority was involved in more than 61% of drownings in places not designated for bathing. CONCLUSIONS: The results are comparable to those of other studies worldwide. Boys drown twice as much as girls, mainly in the age group of 15-17. This may be explained by overconfidence in boys and a tendency to overestimate their actual swimming abilities. Most drownings occur in pools. Drowning among the Jewish population occurs mainly in designated bathing sites. PRACTICAL APPLICATIONS: The findings can and, in fact, must be used to inform and educate the younger generation as to the potential dangers involving bathing in designated bathing sites.

[SOCIAL IMPACT BONDS FOR HEALTH PROMOTION AND PREVENTIVE MEDICINE].

INTRODUCTION: The World Health Organization (WHO) has declared obesity a global epidemic. WHO sheds much light on this matter in its publications on health promotion and preventative medicine. Lack of physical activity, an unbalanced diet and an unhealthy lifestyle are the leading causes of developing obesity and chronic diseases. In Israel, the growing rate of obesity is a reason for concern. About 500,000 diabetics, mainly as a result of obesity, live in Israel today and by 2030 the number is expected to rise to 2,000,000. Every third child born is expected to develop diabetes by the time they reach the age of 40 unless a profound change is made in health policy. The State of Israel recognizes its responsibility in promoting awareness against obesity as well as its role in prevention. In spite of the country's recognition of the problem, it still has not managed to implement long term solutions which address the issue. Therefore, creative and innovative solutions are called for. The social impact bond (SIB), a newly developed financial model is a possible solution. This model suggests the entry of private investors into the public sector, a field which is within the responsibility of the government. The private investor will be in charge of running a social program on a topic which will be finalized with the government. The private investor and the government will have a contract outlining the program and the criteria for the evaluation and the success of the program. To note, the private investor will only be paid according to the success of the program. Thus the purpose of SIB is in motion processes and is set to serve as a model for several years, and then the authorities will take over the responsibility and continue with the program that the SIB handled. In March 2016, a new SIB was launched in Israel to prevent Type 2 diabetes. This involves 2250 pre-diabetic adults who are at risk to develop Type 2 diabetes and will be identified by their Health Maintenance Organizations (HMOs, Clalit and Leumit) through blood tests. The participants will take part in an intensive intervention wellness program during 3 years. This SIB aims to prevent the onset of diabetes. If successful, and a significant reduction in Type 2 diabetes is found, there will be substantial savings for the HMOs and the National Insurance Institute, which will in turn repay the investors for their expenses, according to the signed contract. This SIB will serve as a pilot project for diabetes prevention and if successful, this model can be adopted for other projects in preventive medicine and health promotion. Thereby, we may be facing a dramatic change in the paradigm of funding national health services in Israel.

Functional polymorphisms in the P2X7 receptor gene are associated with stress fracture injury.

Military recruits and elite athletes are susceptible to stress fracture injuries. Genetic predisposition has been postulated to have a role in their development. The P2X7 receptor (P2X7R) gene, a key regulator of bone remodelling, is a genetic candidate that may contribute to stress fracture predisposition. The aim of this study is to evaluate the putative contribution of P2X7R to stress fracture injury in two separate cohorts, military personnel and elite athletes. In 210 Israeli Defense Forces (IDF) military conscripts, stress fracture injury was diagnosed (n = 43) based on symptoms and a positive bone scan. In a separate cohort of 518 elite athletes, self-reported medical imaging scan-certified stress fracture injuries were recorded (n = 125). Non-stress fracture controls were identified from these cohorts who had a normal bone scan or no history or symptoms of stress fracture injury. Study participants were genotyped for functional SNPs within the P2X7R gene using proprietary fluorescence-based competitive allele-specific PCR assay. Pearson's chi-squared (χ (2)) tests, corrected for multiple comparisons, were used to assess associations in genotype frequencies. The variant allele of P2X7R SNP rs3751143 (Glu496Ala-loss of function) was associated with stress fracture injury, whilst the variant allele of rs1718119 (Ala348Thr-gain of function) was associated with a reduced occurrence of stress fracture injury in military conscripts (P < 0.05). The association of the variant allele of rs3751143 with stress fractures was replicated in elite athletes (P < 0.05), whereas the variant allele of rs1718119 was also associated with reduced multiple stress fracture cases in elite athletes (P < 0.05). The association between independent P2X7R polymorphisms with stress fracture prevalence supports the role of a genetic predisposition in the development of stress fracture injury.

Critical Velocity Is Associated With Combat-Specific Performance Measures in a Special Forces Unit.

The purpose of this study was to examine the relationship between critical velocity (CV) and anaerobic distance capacity (ADC) to combat-specific tasks (CST) in a special forces (SFs) unit. Eighteen male soldiers (mean ± SD; age: 19.9 ± 0.8 years; height: 177.6 ± 6.6 cm; body mass: 74.1 ± 5.8 kg; body mass index [BMI]: 23.52 ± 1.63) from an SF unit of the Israel Defense Forces volunteered to complete a 3-minute all-out run along with CST (2.5-km run, 50-m casualty carry, and 30-m repeated sprints with "rush" shooting [RPTDS]). Estimates of CV and ADC from the 3-minute all-out run were determined from data downloaded from a global position system device worn by each soldier, with CV calculated as the average velocity of the final 30 seconds of the run and ADC as the velocity-time integral above CV. Critical velocity exhibited significant negative correlations with the 2.5-km run time (r = -0.62, p < 0.01) and RPTDS time (r = -0.71, p < 0.01). In addition, CV was positively correlated with the average velocity during the 2.5-km run (r = 0.64, p < 0.01). Stepwise regression identified CV as the most significant performance measure associated with the 2.5-km run time, whereas BMI and CV measures were significant predictors of RPTDS time (R(2) = 0.67, p ≤ 0.05). Using the 3-minute all-out run as a testing measurement in combat, personnel may offer a more efficient and simpler way in assessing both aerobic and anaerobic capabilities (CV and ADC) within a relatively large sample.

ß-Alanine supplementation and military performance.

During sustained high-intensity military training or simulated combat exercises, significant decreases in physical performance measures are often seen. The use of dietary supplements is becoming increasingly popular among military personnel, with more than half of the US soldiers deployed or garrisoned reported to using dietary supplements. ß-Alanine is a popular supplement used primarily by strength and power athletes to enhance performance, as well as training aimed at improving muscle growth, strength and power. However, there is limited research examining the efficacy of ß-alanine in soldiers conducting operationally relevant tasks. The gains brought about by ß-alanine use by selected competitive athletes appears to be relevant also for certain physiological demands common to military personnel during part of their training program. Medical and health personnel within the military are expected to extrapolate and implement relevant knowledge and doctrine from research performed on other population groups. The evidence supporting the use of ß-alanine in competitive and recreational athletic populations suggests that similar benefits would also be observed among tactical athletes. However, recent studies in military personnel have provided direct evidence supporting the use of ß-alanine supplementation for enhancing combat-specific performance. This appears to be most relevant for high-intensity activities lasting 60-300 s. Further, limited evidence has recently been presented suggesting that ß-alanine supplementation may enhance cognitive function and promote resiliency during highly stressful situations.

ß-Alanine ingestion increases muscle carnosine content and combat specific performance in soldiers.

The purpose of this study was to examine the effect of ß-alanine (BA) ingestion on tissue carnosine levels and the impact such changes would have on combat specific activity. Eighteen soldiers (19.9 ± 0.8 year) from an elite combat unit were randomly assigned to either a BA or placebo (PL) group. Before and following a 30-day supplementation period carnosine content of the gastrocnemius muscle and brain was determined by proton magnetic resonance spectroscopy. During each testing session, participants performed military relevant tasks that included a 2.5 km run, a 1-min sprint, 50-m casualty carry, repeated 30-m sprints with target shooting, and a 2-min serial subtraction test (SST) to assess cognitive function under stressful conditions. A significant elevation (p = 0.048) in muscle carnosine content was noted in BA compared to PL. Changes in muscle carnosine content was correlated to changes in fatigue rate (r = 0.633, p = 0.06). No changes (p = 0.607) were observed in brain carnosine content. Following supplementation, no differences were noted in 2.5 km run, 1-min sprint, repeated sprint, or marksmanship performance, but participants in BA significantly (p = 0.044) improved their time for the 50-m casualty carry and increased their performance (p = 0.022) in the SST compared to PL. In summary, 30-days of BA ingestion can increase muscle carnosine content and improve aspects of military specific performance. Although cognitive performance was significantly greater in participants consuming BA compared to placebo, current study methods were unable to detect any change in brain carnosine levels, thus, the precise mechanism underlying these effects remains elusive.

Tibial stress changes in new combat recruits for special forces: patterns and timing at MR imaging.

PURPOSE: To characterize the incidence, location, grade, and patterns of magnetic resonance (MR) imaging findings in the tibia in asymptomatic recruits before and after 4-month basic training and to investigate whether MR imaging parameters correlated with pretraining activity levels or with future symptomatic injury. MATERIALS AND METHODS: This study was approved by three institutional review boards and was conducted in compliance with HIPAA requirements. Volunteers were included in the study after they signed informed consent forms. MR imaging of the tibia of 55 men entering the Israeli Special Forces was performed on recruitment day and after basic training. Ten recruits who did not perform vigorous self-training prior to and during service served as control subjects. MR imaging studies in all recruits were evaluated for presence, type, length, and location of bone stress changes in the tibia. Anthropometric measurements and activity history data were collected. Relationships between bone stress changes, physical activity, and clinical findings and between lesion size and progression were analyzed. RESULTS: Bone stress changes were seen in 35 of 55 recruits (in 26 recruits at time 0 and in nine recruits after basic training). Most bone stress changes consisted of endosteal marrow edema. Approximately 50% of bone stress changes occurred between the middle and distal thirds of the tibia. Lesion size at time 0 had significant correlation with progression. All endosteal findings smaller than 100 mm resolved or did not change, while most findings larger than 100 mm progressed. Of 10 control subjects, one had bone stress changes at time 0, and one had bone stress changes at 4 months. CONCLUSION: Most tibial bone stress changes occurred before basic training, were usually endosteal, occurred between the middle and distal thirds of the tibia, were smaller than 100 mm, and did not progress. These findings are presumed to represent normal bone remodeling.

Novel candidate genes putatively involved in stress fracture predisposition detected by whole-exome sequencing.

While genetic factors in all likelihood contribute to stress fracture (SF) pathogenesis, a few studies focusing on candidate genes have previously been reported. The objective of this study is to gain better understanding on the genetic basis of SF in a gene-naive manner. Exome sequence capture followed by massive parallel sequencing of two pooled DNA samples from Israeli combat soldiers was employed: cases with high grade SF and ethnically matched healthy controls. The resulting sequence variants were individually verified using the Sequenom™ platform and the contribution of the genetic alterations was validated in a second cohort of cases and controls. In the discovery set that included DNA pool of cases (n = 34) and controls (n = 60), a total of 1174 variants with >600 reads/variant/DNA pool were identified, and 146 (in 127 genes) of these exhibited statistically significant (P < 0·05) different rates between SF cases and controls after multiple comparisons correction. Subsequent validation of these 146 sequence variants individually in a total of 136 SF cases and 127 controls using the Sequenom™ platform validated 20/146 variants. Of these, three missense mutations (rs7426114, rs4073918, rs3752135 in the NEB, SLC6A18 and SIGLEC12 genes, respectively) and three synonymous mutations (rs2071856, rs2515941, rs716745 in the ELFN2, GRK4, LRRC55 genes) displayed significant different rates in SF cases compared with controls. Exome sequencing seemingly unravelled novel candidate genes as involved in SF pathogenesis and predisposition.

Ad libitum caffeine consumption, cognitive performance, and sleep in special forces soldiers during a 96-h combat exercise.

Introduction: This observational study investigated the effects of sleep deprivation and ad libitum caffeine consumption on cognitive performance, risk behavior, and mood among 28 Israeli Special Forces (SF) soldiers (mean age: 20.57 ± 0.92 years) during a 96-hour combat exercise. Methods: Actigraphy was used to monitor sleep and activity; cognitive function, risk-taking propensity, mood states, and self-reported sleepiness were assessed using the Psychomotor Vigilance Task (PVT), Evaluation of Risks Scale (EVAR), Profile of Mood States (POMS), Karolinska Sleepiness Scale (KSS); and caffeine consumption by questionnaire at 0, 50, and 96 hours. For analyses, participants were divided into Low (<400 mg) and High (≥400 mg) caffeine consumption groups. Results: The soldiers hiked 108.5 ± 0.52 km and slept for 12.7 ± 0.5 h, with a notable transition from multiple short sleep epochs in the initial 50 hours to a consolidated 5-hour sleep period subsequently. In the High caffeine group, PVT reaction time was faster (p = 0.024) compared to the Low caffeine group, with fewer premature response errors (p = 0.026). However, this group showed increased risk-taking (p = 0.037), particularly reduced Self-Control (p = 0.010). No significant impact of ad libitum caffeine intake on mood was observed. However, degradation over the course of the exercise in both groups in mood states, including anger, fatigue, tension, and vigor, was noted (p < 0.05). KSS scores increased significantly at 50 and 96 h (p < 0.001). Discussion: These results suggest that while caffeine enhances cognitive function, its ad libitum consumption did not consistently improve these measures in this cohort of SF soldiers. The study highlights the complex relationship between sleep deprivation and caffeine intake and their combined effects on soldiers' cognitive and behavioral functions, indicating a need for evidence-based caffeine use guidelines for using caffeine in military settings.

The effect of air permeability characteristics of protective garments on the induced physiological strain under exercise-heat stress.

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. METHODS: Twelve young (20-30 years) healthy, heat-acclimated male subjects were exposed fully encapsulated for 3h daily to an exercise-heat stress (35°C and 30% relative humidity, walking on a motor-driven treadmill at a pace of 5 km h(1) and a 4% inclination, in a work-rest cycle of 45 min work and 15 min rest). Two bipack CPCs (PC1 and PC2) were tested and the results were compared with those attained by two control suits-a standard cotton military BDU (CO1) and an impermeable material suit (CO2). RESULTS: The physiological burden imposed by the two bilayer garments was within the boundaries set by the control conditions. Overall, PC2 induced a lower strain, which was closer to CO1, whereas PC1 was closer to CO2. Air permeability of the PC2 cloth was almost three times higher than that of PC1, enabling a better heat dissipation and consequently a lower physiological strain. Furthermore, air permeability characteristic of the fabrics, which is associated with its construction and weave, significantly correlated with the physiological strain, whereas the correlation with Rct, Ret, and weight was poor. CONCLUSIONS: The results emphasize the importance of air permeability in reducing the physiological strain induced by CPCs.

Physiological employment standards IV: integration of women in combat units physiological and medical considerations.

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 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 disadvantage compared with men in carrying out 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 and are at increased risk of overuse injuries. Their smaller size, different bone geometry and lower bone strength also predispose women to a higher incidence of stress fractures. Although training in gender-integrated groups narrows the gaps in fitness, significant differences between the genders after basic training still remain. Nevertheless, integration of women into military combat professions is feasible in many cases. Some 'close combat roles' will still be an exception, mainly because of the extreme physical demands that are required in those units that are beyond the physiological adaptability capacities of an average female. There is no direct evidence that women have a negative impact on combat effectiveness. Once the gender differences are acknowledged and operational doctrines adjusted accordingly, female soldiers in mixed-gender units can meet the physical standards for the assigned missions.

Bone turnover markers do not predict stress fracture in elite combat recruits.

BACKGROUND: With bone resorption rates greater than formation, stress fracture pathogenesis plausibly involves bone remodeling imbalance. If this is the case, one would anticipate serum levels of bone turnover markers would be higher in patients with stress fractures than in those without. QUESTIONS/PURPOSES: We therefore asked whether: (1) bone turnover markers differ between soldiers who will or will not have stress fractures during basic training; (2) bone turnover markers change during basic training; and (3) serial bone formation or bone resorption markers differ between subjects with and without stress fractures during basic training? METHODS: We performed serial determinations of serum bone formation (bone alkaline phosphatase [BAP] and procollagen type I amino-terminal propeptide [PINP]), and resorption (tartrate-resistant acid phosphatase [TRAP5b] and cross-linked collagen telopeptide [CTx]) biomarkers, measured at 2- to 4-week intervals (during 18 weeks) in 69 male soldiers in the Israeli Defense Forces during elite basic training. Twenty-two soldiers (32%) were diagnosed with stress fractures. The mean training week at diagnosis was 8.0±2.0 weeks. RESULTS: We observed no differences in bone turnover markers between soldiers with and without stress fractures. During basic training, the mean values of all subjects for bone turnover markers (BAP, PINP, and CTx) changed in comparison to their mean levels at induction (43.9 versus 37.3 µg/L, 110.4 versus 78.0 µg/L, 1.4 versus 1.1 ng/mL, respectively). We found no changes in bone formation and resorption markers between subjects with and without stress fractures. CONCLUSIONS: These specific bone turnover markers cannot be considered as either diagnostic or predictive tools for stress fracture detection in young male military recruits. LEVEL OF EVIDENCE: Level II prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Hand Grip Strength Relative to Waist Circumference as a Means to Identify Men and Women Possessing Intact Mobility in a Cohort of Older Adults with Type 2 Diabetes.

Possessing intact mobility in older adults assures their continued independence. The early identification of reduced mobility in older adults with type 2 diabetes (T2DM) is paramount for preventing their future physical deterioration. Hand grip strength (HGS), relative to body size, is associated with mobility in older T2DM patients. This study aims to identify an HGS index that best identifies mobilityintact older T2DM patients, along with its optimal cut-off point. The baseline data are from a cohort of 122 older T2DM patients (59% women) (mean age of 70.2 ± 4.4 years). Three mobility tests encompassing three main mobility domains were measured, including usual gait speed (UGS), timed up and go (TUG), and a two-minute walk test (2MWT). Passing scores were defined as those either above the established cut-off points or above the 25th percentile of population norms. Passing all three tests was considered as possessing intact mobility. Receiver operating characteristic (ROC) curves of the most relevant HGS indices were constructed to determine the area under the curve (AUC) that best identifies patients with intact mobility. In a sample of 122 older adults with T2DM, 63.9% of women and 60% of men were found to possess intact mobility. HGS relative to waist circumference (WC) was found to have the strongest association with intact mobility, presenting the highest AUC in both men (0.78) and women (0.72) for discriminating mobility status, with an optimal cut-off of 0.355 (kg/cm) and 0.245 (kg/cm) in men and women, respectively. HGS relative to WC best differentiated between mobility-intact older adults with T2DM and those with mobility limitations, especially in men. Using HGS/WC as a simple and safe screening mode for mobility in a clinical setting could potentially identify older patients with T2DM that require therapeutic interventions.

Beating the heat: military training and operations in the era of global warming.

Global climate change has resulted in an increase in the number and intensity of environmental heat waves, both in areas traditionally associated with hot temperatures and in areas where heat waves did not previously occur. For military communities around the world, these changes pose progressively increasing risks of heat-related illnesses and interference with training sessions. This is a significant and persistent "noncombat threat" to both training and operational activities of military personnel. In addition to these important health and safety concerns, there are broader implications in terms of the ability of worldwide security forces to effectively do their job (particularly in areas that historically already have high ambient temperatures). In the present review, we attempt to quantify the impact of climate change on various aspects of military training and performance. We also summarize ongoing research efforts designed to minimize and/or prevent heat injuries and illness. In terms of future approaches, we propose the need to "think outside the box" for a more effective training/schedule paradigm. One approach may be to investigate potential impacts of a reversal of sleep-wake cycles during basic training during the hot months of the year, to minimize the usual increase in heat-related injuries, and to enhance the capacity for physical training and combat performance. Regardless of which approaches are taken, a central feature of successful present and future interventions will be that they are rigorously tested using integrative physiological approaches.

Do the rotator cuff tendons of young athletic subjects hypertrophy in response to increased loading demands?

BACKGROUND: The rotator cuff is composed of muscle and tendon units. Although muscle has been shown to adapt to mechanical loads, the response of human tendon is not well defined. We hypothesized that increased loading demands on the rotator cuff of young trainees would cause an adaptive muscle response but not an adaptive hypertrophic tendon response. METHODS: The hypertrophic response of the rotator cuff tendon, shoulder strength, aerobic fitness, and the lean body weight of 70 young male recruits were studied before and after a 1-year course of elite infantry training. Shoulder strength was assessed by the maximum number of pull-ups done and the rotator cuff thickness by ultrasound measurement of the supraspinatus thickness. Aerobic physical fitness was assessed by maximum oxygen consumption (Vo(2) max). Lean body weight was measured by skin-fold thickness. RESULTS: The mean number of pull-ups done increased from 17.5 to 21.7 (P = .01), but the supraspinatus thickness at the beginning of training (6.1 mm) was unchanged at the end of the training. Vo(2) max increased from 57 to 64 mL/kg/min (P = .0001). Lean body weight increased from 58.3 to 64.7 kg (P = .0001). CONCLUSIONS: As a result of increased loading, the strength of the rotator cuff muscles of young trainees increased, but by the parameter of hypertrophy, no evidence was found of a parallel adaptive response of the rotator cuff tendon.

A simplified model to predict stress fracture in young elite combat recruits.

The purpose of the study was to develop a simple prediction model for stress fractures (SFs) in young male recruits to identify risk factors for SF. Data were collected from 57 young (18.5 ± 0.5 years) male athletes before elite combat basic training (BT). Measurements included anthropometric variables, blood samples, fitness tests, bone quality (peripheral quantitative computed tomography [pQCT]), psychological assessment, nutritional habits, and history of physical activity. A medical evaluation was done periodically. The SFs were clinically diagnosed during the 1-year training and thereafter confirmed by bone scintigraphy. Three "simple to monitor" variables were found to be significantly (p < 0.05) related to SF occurrence during basic and advanced training: aerobic training frequency, aerobic training duration, and waist circumference. From these 3 variables, a new model was constructed that successfully predicted 85% of the soldiers with (n = 23) and without (n = 34) SF as follows:(Equation is included in full-text article.)where PSF is the stress fracture prediction according to the Log Odds (SF), Odds(SF) is the ratio between the probability of SF existence and nonexistence, ATn is the aerobic training (times per week), ATt is the aerobic training duration (minutes per week), and waist is the circumference (centimeters). This model was validated on a different database taken from another 59 elite combat recruits before BT and successfully predicted 76.5% of the soldiers with SF (n = 22) and without SF (n = 37). A young male recruit for elite combat unit is at a greater risk of developing SF if, before entering BT, he trained aerobically <2 times per week with each training >40 minutes and has a waist circumference of <75 cm. However, further evaluation is required for different combat recruits, ages, and training programs to validate these results.

IGF-I, IGFBPs, and inflammatory cytokine responses during gender-integrated Israeli Army basic combat training.

Insulin-like growth factor 1 (IGF-I) is a robust metabolic and anabolic biomarker that has been demonstrated to be reflective of military training-induced body composition changes and influenced by initial aerobic fitness level. Greater mechanistic insight into the IGF-I response to physical training can potentially be gleaned by also examining other regulatory factors that influence IGF-I biological activity (i.e., insulin-like growth factor-binding proteins [IGFBPs] and inflammatory cytokine responses). The purpose of this study was to assess the influence of sex and initial fitness level on the IGF-I and inflammatory cytokine response to gender-integrated Israeli Defense Forces (IDF) basic combat training (BCT). Recruits (29 men, 19.1 ± 1.3 years; 93 women, 18.8 ± 0.6 years) were recruited from a 4-month gender-integrated BCT of the IDF. Blood was drawn and assayed for total IGF-I, free IGF-I, IGFBPs 1-6, tumor necrosis factor alpha (TNF-α), interleukin 6, and interleukin 1 beta. Body composition was determined via a 4-site skinfold (biceps, triceps, suprailiac, and subscapular) equation. Physical performance was assessed via a maximum volume of oxygen consumption (V[Combining Dot Above]O2max) test using a treadmill protocol. All measures were obtained pre- and posttraining. A 2-way (sex × time) analysis of variance was used to test for statistical differences (p ≤ 0.05). Additionally, subjects were further partitioned (men and women separately) by tertiles of initial V[Combining Dot Above]O2max to assess the influence of initial fitness level on the IGF-I system and inflammatory cytokine responses to physical training. Pearson product moment correlational analysis was also used to examine relationships between percent changes in blood measures and physical performance and body composition changes. All data are presented as mean ± SE. Time effects were observed only for total IGF-I, IGFBP-2, TNF-α, V[Combining Dot Above]O2max, fat-free mass, and fat mass. The only significant (p ≤ 0.05) correlations observed for percent changes were in men between total IGF-I and V[Combining Dot Above]O2max (r = 0.49) and body mass (r = -0.42) During gender-integrated Israeli Army BCT, men and women generally respond in a similar fashion with regard to blood measures (IGF-I system and inflammatory cytokines) and V[Combining Dot Above]O2max. Initial fitness level only influenced the IGF-I response to training in women. Although the training-induced changes in total IGF-I (increase), IGFBP-2 (decrease), and TNF-α (decrease) are all indicative of an enhanced circulating anabolic milieu, only total IGF-I for the men was correlated with body composition and fitness improvements.

Heat acclimation and performance in hypoxic conditions.

INTRODUCTION: 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. METHODS: Eight young healthy men participated in this study. They went through two cognitive tests: Visual Vigilance Task (VVT) and Four Choice Reaction Time (FCRT); through a Dynamic Posture Test (DPT); and through an exercise onset of blood lactate accumulation rate (OBLA) test under moderate hypoxia (O2 = 15.6%) before and after 12 d of heat acclimation. RESULTS: Maximal heart rate and core temperature were lower during the last day of heat acclimation compared to baseline (103 +/- 14 compared to 115 +/- 13 bpm and 37.59 +/- 0.20 compared to 37.83 +/- 0.28 degrees C, respectively). OBLA was higher after heat acclimation under both normoxic and hypoxic conditions. Blood oxygen saturation during walking at a pace of 7 km/h in hypoxic conditions was higher after heat acclimation compared to baseline (88 +/- 2% and 86.5 +/- 2%, respectively). Average steps during DPT in hypoxic conditions increased from 4.083 +/- 0.044 to 4.75 +/- 0.326 after heat acclimation. The VVT results under hypoxia did not change after heat acclimation, but false positive results were lower. The FCRT test results improved after heat acclimation (475 +/- 30 ms compared to 500 +/- 24 ms). CONCLUSIONS: Prior heat acclimation may reduce physiological strain and improve cognitive performance in moderate hypoxia. Further studies are required in order to evaluate the possibility of implementing this method as an operational preconditioning tool.

[Fluid and sodium balance during exercise--standpoint].

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 the reduction in physical and cognitive performance. It is recommended to drink water frequently and in small amounts. In order to encourage drinking, the fluid should be cool, palatable, readily available, and not carbonated. During exercise the ability of the kidney to excrete water is restricted, and therefore, there is a risk of hyperhydration and hyponatremia, mainly under conditions of overdrinking. Sodium loss through sweating and the development of hyponatremia will primarily occur during strenuous exercise lasting more than 4 hours. Symptoms of hyponatremia will generally appear at sodium concentrations below 130 mmol/l. In order to avoid hyponatremia one must avoid overdrinking, and during prolonged physical activity (> 4 hours) sodium intake must match the amount lost by sweating. Proper electrolyte and carbohydrate consumption through a normal diet is preferable to sport beverages or exogenous sodium supplements. In order to avoid dehydration, on one hand, and hyponatremia due to hyperhydration, on the other hand, the amount of fluid consumed should complement the amount of fluid lost during exercise. Given that there is intra- (depending on the type of activity and environmental conditions) and interindividual variability in the rate of fluid and salt loss, fluid and salt intake should be determined on an individual basis, as outlined in this standpoint.