Voluntary Dehydration Research Articles

Oliguria caused by dehydration in combat trauma (case series)

Background. A combat gunshot wound is significantly different from a civilian trauma. It is characterized by the prevalence of penetrating injuries, which increases the volume of blood loss at the pre-hospital stage, and the destruction of large masses of muscle tissue (rhabdomyolysis), which leads to acute kidney injury. Moreover, combat trauma occurs in conditions of chronic background stress as a result of severe emotional and physical strain, uncomfortable weather conditions, and deprivation of sleep, drinking and food. So, such a phenomenon as voluntary dehydration is common among soldiers in combat conditions. In wounded, oliguria is often considered a result of acute kidney injury, but it can also be a symptom of severe dehydration. The purpose of our work was to analyze three clinical cases of oliguria caused by dehydration in wounded with combat trauma to better understand the severity of the condition of such victims and to improve medical aid for them. Materials and methods. The article describes three cases of men aged 35, 50 and 44 years with combat gunshot wounds to the extremities, who were admitted to the tertiary care hospital on the second day after the injury with oliguria (0.18–0.19 ml/kg/hr) and high creatinine (333 to 457 μmol/L). Results. All three patients were conscious, breathing spontaneously, had stable hemodynamics, and moderate anemia after pre-hospital blood transfusions. Focused ultrasound study revealed hyperdynamic left ventricle and small inferior vena cava with complete inspiratory collapse, which suggested hypovolemia. Upon further investigation of the medical history, patients admitted not drinking any liquid for one to two days prior to injury. Tissue hydrophilicity test was conducted which showed severe dehydration in all three cases. Infusion volume was calculated using P.I. Shelestiuk nomogram (modified by O.V. Kravets et al.) and amounted to 60 ml/kg of balanced crystalloid solutions. Upon starting rehydration, diuresis was restored within two hours and amounted to 0.7–2.1 ml/kg/h in all three patients. Creatinine levels normalized in 2–4 days. Patients were transferred to another hospital in a moderate condition in 4–5 days. Conclusions. Oliguria is a frequent complication of combat gunshot injury. Although it is most often associated with acute kidney injury from rhabdomyolysis, it should also be considered that in a combat environment, soldiers’ access to water may be limited and the injury may be accompanied by dehydration. In the cases presented, the differential diagnosis of the causes of oliguria in the wounded made it possible to detect signs of severe dehydration, abstain from the inappropriate use of saluretics, quickly compensate for the fluid deficit, and to avoid the development of kidney damage and the need for renal replacement therapy.

Current Hydration Habits: The Disregarded Factor for the Development of Renal and Cardiometabolic Diseases.

Improper hydration habits are commonly disregarded as a risk factor for the development of chronic diseases. Consuming an intake of water below recommendations (underhydration) in addition to the substitution of sugar-sweetened beverages (SSB) for water are habits deeply ingrained in several countries. This behavior is due to voluntary and involuntary dehydration; and because young children are exposed to SSB, the preference for a sweet taste is profoundly implanted in the brain. Underhydration and SSB intake lead to mild hyperosmolarity, which stimulates biologic processes, such as the stimulation of vasopressin and the polyol-fructose pathway, which restore osmolarity to normal but at the expense of the continued activation of these biological systems. Unfortunately, chronic activation of the vasopressin and polyol-fructose pathways has been shown to mediate many diseases, such as obesity, diabetes, metabolic syndrome, chronic kidney disease, and cardiovascular disease. It is therefore urgent that we encourage educational and promotional campaigns that promote the evaluation of personal hydration status, a greater intake of potable water, and a reduction or complete halting of the drinking of SSB.

Early Detection of Exercise - Associated Muscle cramp

One of the deep and painful involuntary contractions of skeletal muscle is muscle cramp which takes place during various other conditions. The origin for the cramps that occur during or soon after exercise and the appropriate remedies continue to prove uncertain. Soon after an implant process and forceful workout, past voluntary dehydration cramps occur at many sections. The process of identifying the type of cramp is time consuming and treatment process to cramps is also quite tedious. If not treated at the right time, Muscle cramps may cause vigorous side effects and worsening in day to day physiological activities. The main motive of this vest is to locate and identify the cramp and alert so that further injury can be detected. It would also be helpful in preventing the person from further muscular cramps and other complications. EMG signals which are obtained from adhesive electrodes are amplified by using IC741 (op-amp) with instrumentation amplifier configuration.LM35 temperature sensor is used to monitor the temperature at specified locations. Wherever the cramp occurring possibilities are high. Flex sensor is used to identify the abnormal contraction and relaxation muscles in upper limbs. The three input bio potential signals are fed to the micro controller (Arduino UNO). The main objective of this system is to provide a comfortable vest which would monitor the cramps occurring in athletes whenever it occurs. Therefore with the help of this wearable device muscle cramps occurring at upper limbs can be detected and further injuries, complications such as fractures can be reduced.

Detection of voluntary dehydration in paediatric populations using non‐invasive point‐of‐care saliva and urine testing

Voluntary dehydration, or lack of fluid intake despite water availability, is common in otherwise healthy children, and can lead to adverse effects. Most dehydration biomarkers are impractical for routine assessment in paediatric populations. This study aimed to assess two non-invasive hydration assessment tools, urine specific gravity (USG ) and a novel point-of-care (POC) salivary osmolarity (SOSM) sensor, in healthy children. Volunteers were tested by colorimetric USG and a handheld SOSM system. Observed values were compared against previous studies to determine hydration status, as was the concordance between parameters. At the common USG threshold of 1.020, 42.4% of the 139 healthy children were dehydrated. The same prevalence was found using the 70-mOSM cut-off value. Comparative analysis of SOSM at varying USG thresholds demonstrated significantly higher SOSM in dehydrated children with a USG ≥ 1.030 (P= 0.002). At the USG threshold of 1.020 and SOSM threshold of 70 mOSM, 42.4% of healthy children were found to be voluntarily dehydrated. Significantly higher SOSM was observed in dehydrated children (USG ≥ 1.030). As the first study on the utility of POC SOSM measurements for detecting dehydration, these results provide a foundation for future POC characterisation of SOSM in other populations and clinical contexts.

Mild dehydration following voluntary water intake reduction does not affect anaerobic power performance.

Dehydration is common among athletes. The negative impact of dehydration on aerobic performance is well characterized. However, little is known about the effect of dehydration on anaerobic performance particularly when dehydration results from insufficient water intake, not water loss due to body temperature regulation. The purpose of this study was to examine the effect of dehydration on anaerobic performance following voluntary water intake reduction. Fifteen healthy adults completed two exercise sessions, euhydrated (EUD) and dehydrated (DEH). Sessions consisted of baseline anthropometric and blood lactate measurement followed by a 30-second Wingate test and three vertical jump trials to measure anaerobic performance. Additional blood lactate measurements were taken immediately and at 5, 10, and 15 minutes after taking the Wingate test. The dehydration protocol resulted in a reduction in body mass (EUD 69.1±17.2 kg, DEH 68.1±16.6 kg, P=0.039). The 30-s Wingate peak power (EUD 971±302 W, DEH 960±316 W, P=0.578) was not different between conditions, nor was the vertical jump height (EUH 26.4±4.5 cm, DEH 26.6±3.6 cm, P=0.778). Blood lactate (P<0.001) was elevated immediately following the 30-s Wingate test which remained throughout the trial. There were no differences in blood lactate between conditions. Acute anaerobic power and exercise performance is not negatively affected by voluntary dehydration.

The effect of voluntary fasting and dehydration on posterior ocular structures

Purpose: Islamic Ramadan is the month of fasting, in which intake of food and drink is restricted from sunrise until sunset. The objective of the present study was to find out the effects of religious fasting on posterior ocular structures.Materials and methods: In this prospective study, 34 eyes of 34 healthy volunteers with a mean age of 34.09 ± 7.20 years were enrolled. Volunteers with any systemic disorder and eyes with pathology or previous surgery were excluded. One week before Ramadan (non-fasting period) and during Ramadan (fasting period) at the same hours (at 08:00 and 16:00 h), choroidal, macular, and retinal nerve fibre layer (RNFL) thicknesses were measured by spectral domain optical coherence tomography. Results were compared using paired sample t-test, and a p value <0.05 was accepted as statistically significant.Results: The comparison of 16:00-h measurements significantly revealed lower values during fasting period when compared non-fasting period for choroidal thickness (non-fasting and fasting, respectively; subfoveal: 299.26 ± 41.3 and 280.03 ± 38.75 p < 0.001, nasal: 246.09 ± 53.59 and 227.06 ± 53.82 p < 0.001, and temporal: 273.56 ± 42.68 and 257.44 ± 45.06 p = 0.001) and paracentral macular thickness (superior: p = 0.002, inferior: p = 0.010, temporal: p = 0.013, and nasal: p = 0.016). By contrast, no significant differences were found in the central macular thickness between the fasting and non-fasting periods (p = 0.735). Also, no statistically significant difference was noted for RNFL thickness at the different periods and time points.Conclusion: Our results reveal that Islamic religious fasting is associated with statistically significant alterations in choroidal and paracentral macular thickness in healthy volunteers. However, more detailed investigations should be designed to evaluate whether fasting has a pivotal influence on pathological conditions.

Prevalence of voluntary dehydration according to urine osmolarity in elementary school students in the metropolitan region of São Paulo, Brazil

OBJECTIVES:To evaluate the prevalence of voluntary dehydration based on urine osmolarity in elementary school students from two public educational institutions in the metropolitan region of São Paulo and evaluate whether there is a relationship between voluntary dehydration and nutritional status or socioeconomic status.METHODS:Analytical cross-sectional study with students from two public schools in the city of Osasco. The determination of urine osmolarity was performed using the freezing method of the Advanced® Osmometer Model 3W2. Urine osmolarity greater than 800 mOsm/kg H2O was considered voluntary dehydration. During data collection, the weights and heights of the students, environmental temperatures and air humidity levels were obtained.RESULTS:A total of 475 students aged six to 12 years were evaluated, of whom 188 were male. Voluntary dehydration occurred in 63.2% of the students and was more frequent in males than in females. The prevalence of voluntary dehydration was more frequent in males aged six to nine years than in females. However, no statistically significant difference was observed between males and females aged 10 to 12 years. No association was found between voluntary dehydration and nutritional status or socioeconomic status.CONCLUSION:The prevalence of voluntary dehydration was high in elementary school students and was more frequent in males. No association was found between voluntary dehydration and nutritional or socioeconomic status.

Where Can I Find Nutrition Resources for Children and Adolescents Participating in Youth Sports?

In addition to consuming a healthy eating pattern, regular physical activity is one of the most important things all Americans, including children and adolescents, can do to improve their health. The 2008 Physical Activity Guidelines for Americans, published by the US Department of Health and Human Services, describe the types and amounts of physical activity that offer substantial health benefits.1Office of Disease Prevention and Health Promotion. Physical Activity Guidelines. Washington, DC: US Department of Health and Human Services. https://health.gov/paguidelines/. Accessed July 12, 2017.Google Scholar Children and adolescents should do 60 minutes or more of physical activity daily. Most of that time should be spent doing either moderate- or vigorous-intensity aerobic activity. In addition, they should participate in muscle-strengthening and bone-strengthening activities at least 3 days a week. The “Be Active Your Way” blog is the official blog of the Physical Activity Guidelines for Americans, and it provides updates about the development of the second edition of the guidelines and insights from health and physical activity professionals about translating the guidelines into practice.2Office of Disease Prevention and Health Promotion. Be Active Your Way. Washington, DC: US Department of Health and Human Services. https://health.gov/news/category/blog-bayw/. Accessed May 30, 2017.Google Scholar A 2012 mid-course Physical Activity Guidelines report on “Strategies to Increase Physical Activity Among Youth” further emphasized the importance of physical activity for health in children and youth and outlined methods for achieving the recommended 60 minutes of physical activity per day, while noting that fewer than half of children meet the recommendations.3Office of Disease Prevention and Health Promotion. PAG Midcourse Report: Strategies to Increase Physical Activity Among Youth. Washington, DC: US Department of Health and Human Services. https://health.gov/paguidelines/midcourse/. Accessed July 12, 2017.Google Scholar Additional statistics and information about physical activity and health are available on the Centers for Disease Control and Prevention’s physical activity webpage.4National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition, Physical Activity, and Obesity. Facts about Physical Activity. Atlanta, GA: Centers for Disease Control and Prevention. https://www.cdc.gov/physicalactivity/data/facts.htm. Accessed May 30, 2017.Google Scholar Proper nutrition is a major factor that can help make participation in physical activity a positive experience for children and adolescents. Registered dietitian nutritionists may be called upon to talk with coaches, make presentations to players and their parents, or provide personalized nutrition counseling. An excellent resource for sports-related nutrition information is the Pediatric Nutrition Care Manual (PNCM).5Pediatric Nutrition Care Manual. Child athletes. Chicago, IL: Academy of Nutrition and Dietetics. https://www.nutritioncaremanual.org/topic.cfm?ncm_category_id=12&lv1=144615&ncm_toc_id=144615&ncm_heading=&. Accessed May 30, 2017.Google Scholar According to the PNCM, nutrient needs are similar for boys and girls prior to puberty. When a variety of foods are consumed, a child’s diet can meet nutrient needs by following the 2015-2020 Dietary Guidelines for Americans in conjunction with guidelines specified in ChooseMyPlate.gov. The PNCM states that for activities lasting less than 60 minutes, water is all that is needed for hydration. For activities longer than 60 minutes, other beverages, such as fluid-replacement drinks that contain additional carbohydrate and electrolytes, are recommended. Some studies suggest that the presence of flavoring, sodium, and carbohydrate in a beverage enhances thirst and is effective in reducing or preventing voluntary dehydration. Puberty, which occurs during adolescence, is characterized by increases in height and weight, completion of skeletal growth, increases in bone mass, changes in body composition, and sexual maturation. Children enter adolescence and begin puberty at varying ages. These changes result in increased nutrition needs, and optimal nutrition is key. In addition to physical growth, adolescents experience an increase in the ability to assess and address more complex situations and a significant increase in the desire for autonomy. The increased nutrient needs—along with more independence in decision-making regarding food choices and other influences such as peer pressure or the media—may put some adolescents at nutritional risk. Understanding the physical and cognitive changes occurring throughout adolescence can help nutrition and dietetics practitioners working with adolescents. The PNCM provides guidance and resources to assist with meeting the needs of the active child. It also addresses the unique nutritional needs of the child athlete in relation to growth and development and within the context of the Nutrition Care Process. A registered dietitian nutritionist, especially one that specializes in sports nutrition, can be an asset to the child who is becoming more active and to the child athlete who is already participating in sporting events that can vary greatly in skill levels.

Dietary intake according to hydration status in 9-10 year-old soccer players.

Children have an increased risk of voluntary dehydration especially during physical activity which may increase the risk of non-compensating water losses. The aim of this study was to assess the hydration status and its relation to food intake in a children group of soccer players. A sample of 36 boys aged 9-10 years was included in this study; 30 completed a 24 h urine collection. Participants completed a 24 h urine collection; a 24 hours food recall corresponding to the day of urine collection was applied, weight and height were measured and parents/caregivers fi lled a lifestyle and socio-demographic questionnaire. The free water reserve (FWR [ml/24 h] = urine volume [ml/24 h] - obligatory urine volume [ml/24 h]) was used to assess the hydration status. Food and beverage groups were created and models of unconditional logistic regression were fi tted in order to estimate the magnitude of the association between the hydration status and diet. Forty three per cent of participants were classifi ed as at risk of hypohydration. Children who reported a high fruit and vegetables intake (above the median) were at decreased risk of hypohydration (OR = 0.19, 95% CI 0.04-0.94, p = 0.041), compared to children who reported a low fruit and vegetables intake. Almost half of the children were at risk of hypohydration. Our results suggested that water food sources such as fruit and vegetables may contribute to euhydration.

A preliminary study on how hypohydration affects pain perception.

Chronic pain is a prevalent health issue with one in five people suffering from some form of chronic pain, with loss of productivity and medical costs of chronic pain considerable. However, the treatment of pain can be difficult, as pain perception is complex and can be affected by factors other than tissue damage. This study investigated the effect of hypohydration (mild, voluntary dehydration from ∼24 h of limiting fluid intake, mimicking someone drinking less than usual) on a person's pain perception. Seventeen healthy males (age 27 ± 5 years) visited the laboratory on three occasions, once as a familiarization and then twice again while either euhydrated (urine specific gravity: 1.008 ± 0.005) or hypohydrated (urine specific gravity: 1.024 ± 0.003, and -1.4 ± 0.9% body mass). Each visit, they performed a cold pressor test, where their feet were placed in cold water (0-3 °C) for a maximum of 4 min. Measures of hydration status, pain sensitivity, pain threshold, and catastrophization were taken. We found that hypohydration predicted increased pain sensitivity (β = 0.43), trait pain catastrophizing, and baseline pain sensitivity (β = 0.37 and 0.47, respectively). These results are consistent with previous research, and suggest that a person's hydration status may be an important factor in their perception of acute pain.

Salivary nitrite content, cognition and power in Mixed Martial Arts fighters after rapid weight loss: a case study

Rapid weight loss (RWL) is extensively practiced by combat sports athletes, including Mixed Martial Arts (MMA), but its effects on performance are not well established with different magnitudes of RWL, including those higher than 5% of total body weight. The aim of the present study was to follow MMA athletes during RWL with subsequent weight regain to evaluate the responses of isometric strength, power, cognition and salivary nitrite ( ) content. Two professional male MMA fighters, same age, competing in the same weight category underwent two magnitudes of RWL before a simulated competition period. Anthropometric measures, records of nutritional status, training, voluntary dehydration strategies, salivary samples, cognition response, isometric strength and muscular power were obtained: (I) 7 days before combat, (II) at the weigh-in moment, and (III) in the combat day. Athlete 1 lost 7.2 kg (9.1% of total bodyweight) and Athlete 2 lost 4.0 kg (5.3% of total bodyweight). Athlete 1 had a lower and misbalanced caloric ingestion (708 ± 428 kcal), ingested 6 L of water during the first 5 days of RWL, underwent 2 days of fasting, water and sodium restriction before weigh-in. Athlete 2 was supervised by a nutritionist, had a balanced diet (1600 ± 0 kcal), ingested 2 L of water during the first 6 days of RWL, underwent only 1 day of fasting and water restriction, and did not restrict sodium. As expected, there was a negative effect of RWL in the evaluated parameters at the weigh-in moment, while in the combat day, salivary ) content. Two professional male MMA fighters, same age, competing in the same weight category underwent two magnitudes of RWL before a simulated competition period. Anthropometric measures, records of nutritional status, training, voluntary dehydration strategies, salivary samples, cognition response, isometric strength and muscular power were obtained: (I) 7 days before combat, (II) at the weigh-in moment, and (III) in the combat day. Athlete 1 lost 7.2 kg (9.1% of total bodyweight) and Athlete 2 lost 4.0 kg (5.3% of total bodyweight). Athlete 1 had a lower and misbalanced caloric ingestion (708 ± 428 kcal), ingested 6 L of water during the first 5 days of RWL, underwent 2 days of fasting, water and sodium restriction before weigh-in. Athlete 2 was supervised by a nutritionist, had a balanced diet (1600 ± 0 kcal), ingested 2 L of water during the first 6 days of RWL, underwent only 1 day of fasting and water restriction, and did not restrict sodium. As expected, there was a negative effect of RWL in the evaluated parameters at the weigh-in moment, while in the combat day, salivary was not completely reestablished at baseline levels (decreased by 35.9% in Athlete 1 and, 25.2% in Athlete 2, as compared with 7 days before). The athlete who underwent a lower weight loss (5.3%) presented better recovery of cognition and upper limbs power on the combat day as compared with the athlete who lost 9.1% of body weight. Although we cannot precisely conclude, this case report led us to believe that the recovery period between weigh-in and competition may be insufficient for total reestablishment of salivary after RWL, and higher amounts of RWLhave negative impacts on average power and cognition when compared with lower RWL.Relevance for patients: Scientific aspects related with performance in MMA athletes brought to light the absence of studies investigating the recovery of isometric strength, power, cognition and salivary during RWL with subsequent weight regain. This study revealed that athletes from the same categories can adopt different magnitudes of weight loss, and that this procedure impacts several important measures, for example, the reduction of salivary is associated with the lower O2 transport capacity, decreasing muscle performance.

Hydration status using free water reserve in Portuguese adolescents.

Introduction: Few data is available about the hydration status of active adolescents in free living conditions. Cell dehydration may be prevalent in healthy, free-living children at school and they could be in a state of chronic voluntary dehydration. Objective: This study aims to describe hydration status assessed by Free Water Reserve (FWR) in adolescents. Method: Two hundred participants (118 girls), aged 13-18 years completed the study. Urinary volume (ml/d) and urinary osmolality (mosm/kg) were measured by one 24h urinary collection, and coefficient of creatinine was used to validate completeness of urine collections. FWR (measured urine volume minus the obligatory urine volume) was used for characterization of hydration status. Positive values of FWR indicate euhydration, negative values the risk of hypo-hydration. Results: Median urinary volume excretion was 1100.0 ml/d for boys and 1025.0 ml/d for girls (p=0.923). Mean urinary osmolality was 715.7±172.3 mosm/kg for boys and 597.42±193.1 mosm/kg for girls (p=0.247). Median FWR (ml/24h) was positive in both sex groups (173.2 ml/d in boys and 373.2 ml/d in girls); however, 40.2% of boys and 31.4% of girls (p=0.195) were at risk of hypo-hydration status. Conclusions: In this sample of adolescents approximately one third was classified as at risk of hypo-hydration status. Preventive measures to increase the level of total water intake should be considered.

Hypohydration per se affects mood states and executive cognitive processing: results from a face-valid model for studying some consequences of 'voluntary dehydration'

There is limited literature on the effects of a deficit in body water on human cognitive function, with inconsistent and contradictory results. In his critical review of this area Lieberman [1] recommended that typical confounding factors such as the method to induce dehydration (exercise, heat stress, diuretics) and other experimental control (sleep, diet, caffeine) should be considered carefully as little existing research has done so. Few studies have actually assessed what occurs naturally, namely a person simply not drinking sufficiently. The purpose of this study was to measure the cognitive effects of 'not drinking enough' ('voluntary dehydration') when other confounding factors such as sleep, diet and caffeine are controlled.

Intravesical chemotherapy in non-muscle-invasive bladder cancer.

Non-muscle-invasive bladder cancer (NMIBC) is characterized by a tendency for recurrence and capacity for progression. Intravesical instillation therapy has been employed in various clinical settings, which are summarized within this review. Several chemotherapeutic agents have shown clinical efficacy in reducing recurrence rates in the post-transurethral resection of bladder tumor (TURBT) setting, including mitomycin C (MMC), doxorubicin, and epirubicin. Mounting evidence also supports the use of intravesical MMC following nephroureterectomy to reduce later urothelial bladder recurrence. In the adjuvant setting, bacillus Calmette-Guérin (BCG) immunotherapy is an established first-line agent in the management of carcinoma in situ (CIS) and high-grade non muscle invasive urothelial carcinoma (UC). Among high and intermediate-risk patients (based on tumor grade, size, and focality) improvements in disease-free intervals have been seen with adjunctive administration of MMC prior to scheduled BCG dosing. Following failure of first-line intravesical therapy, gemcitabine and valrubicin have demonstrated modest activity, though valrubicin remains the only agent currently Food and Drug Administration (FDA)-approved for the treatment of BCG-refractory CIS. Techniques to optimize intravesical chemotherapy delivery have also been explored including pharmacokinetic methods such as urinary alkalization and voluntary dehydration. Chemohyperthermia and electromotive instillation have been associated with improved freedom from recurrence intervals but may be associated with increased urinary toxicity. Improvements in therapeutic selection may be heralded by novel opportunities for genomic profiling and refinements in clinical risk stratification.

AEROBIC FITNESS, BONE HEALTH, HYDRATION AND EXERTION DURING RACING IN PROFESSIONAL JOCKEYS IN HONG KONG

Jockeys often make weight by methods such as caloric restriction and voluntary dehydration, which may lead to a compromise in muscle and liver glycogen stores and blood glucose concentration, all...

The Quantification of Body Fluid Allostasis During Exercise

The prescription of an optimal fluid intake during exercise has been a controversial subject in sports science for at least the past decade. Only recently have guidelines evolved from 'blanket' prescriptions to more individualised recommendations. Currently the American College of Sports Medicine advise that sufficient fluid should be ingested to ensure that body mass (BM) loss during exercise does not exceed >2% of starting BM so that exercise-associated medical complications will be avoided. Historically, BM changes have been used as a surrogate for fluid loss during exercise. It would be helpful to accurately determine fluid shifts in the body in order to provide physiologically appropriate fluid intake advice. The measurement of total body water via D2O is the most accurate measure to detect changes in body fluid content; other methods, including bioelectrical impedance, are less accurate. Thus, the aim of this review is to convey the current understanding of body fluid allostasis during exercise when drinking according to the dictates of thirst (ad libitum). This review examines the basis for fluid intake prescription with the use of BM, the concepts of 'voluntary and involuntary dehydration' and the major routes by which the body gains and loses fluid during exercise.

Effects of drinking supplementary water at school on cognitive performance in children

We investigated the beneficial effects of drinking supplementary water during the school day on the cognitive performance and transitory subjective states, such as fatigue or vigor, in 168 children aged between 9 and 11years who were living in a hot climate (South Italy, Sardinia). The classes were randomly divided into an intervention group, which received water supplementation, and a control group. Dehydration was determined by urine sampling and was defined as urine osmolality greater than 800mOsm/kg H2O (Katz, Massry, Agomn, & Toor, 1965). The change in the scores from the morning to the afternoon of hydration levels, cognitive performance and transitory subjective states were correlated. In line with a previous observational study that evaluated the hydration status of school children living in a country with a hot climate (Bar-David, Urkin, & Kozminsky, 2005), our results showed that a remarkable proportion of children were in a state of mild, voluntary dehydration at the beginning of the school day (84%). We found a significant negative correlation between dehydration and the auditory number span, which indicates a beneficial effect of drinking supplementary water at school on short-term memory. Moreover, there was a positive correlation between dehydration and performance in the verbal analogy task. The results are discussed in the light of the complexity of the neurobiological mechanisms involved in the relationship between hydration status and cognition.

Fluid balance of elite Brazilian youth soccer players during consecutive days of training

In this study we investigated pre-training hydration status, fluid intake, and sweat loss in 20 elite male Brazilian adolescent soccer players (mean ± s: age 17.2 ± 0.5 years; height 1.76 ± 0.05 m; body mass 69.9 ± 6.0 kg) on three consecutive days of typical training during the qualifying phase of the national soccer league. Urine specific gravity (USG) and body mass changes were evaluated before and after training sessions to estimate hydration status. Players began the days of training mildly hypohydrated (USG > 1.020) and fluid intake did not match fluid losses. It was warmer on Day 1 (33.1 ± 2.4°C and43.4 ± 3.2% relative humidity; P < 0.05) and total estimated sweat losses (2822 ± 530 mL) and fluid intake (1607 ± 460 mL) were significantly higher (P < 0.001) compared with Days 2 and 3. Data also indicate a significant correlation between the extent of sweat loss and the volume of fluid consumed (Day 1: r = 0.560, P = 0.010; Day 2: r = 0.445, P = 0.049; Day 3: r = 0.743, P = 0.0001). We conclude that young, native tropical soccer players arrive hypohydrated to training and that they exhibit voluntary dehydration; therefore, enhancing athletes' self-knowledge of sweat loss during training might help them to consume sufficient fluid to match the sweat losses.

Avaliação da taxa de sudorese de atletas de judô e sua associação com escores subjetivos de fome e apetite

O judô, assim como outros esportes que envolvem categorias de pesos, é uma modalidade em que os atletas apresentam grande risco de hipo-hidratação devido aos processos de desidratação involuntária e/ou voluntária. Sendo assim, o objetivo deste estudo foi avaliar a taxa de sudorese (ml/min) de judocas em um dia de treino e associar o grau de desidratação com alterações subjetivas de fome e apetite. A amostra foi composta por 14 atletas (nove homens e cinco mulheres), com idade média de 19,6 ± 5,9 anos. Para a realização do estudo, foram mensuradas a massa corporal e as taxas subjetivas de fome, apetite e esforço, expressas em uma escala de zero a 10, antes e logo após o treino. A massa corporal foi significantemente menor após o treino (68,8 ± 18,1kg versus 66,9 ± 17,3kg; p &lt; 0,01), com redução de 2,6 ± 1,1%. As taxas de fome e esforço foram significantemente maiores após o exercício (2,1 ± 2,2 versus 4,8 ± 3,6, p = 0,02 e 0 versus 7,2 ± 1,3, p &lt; 0,01), assim como a taxa de apetite por frutas (4,3 ± 3,8 versus 8,0 ± 2,8, p = 0,01). Correlações positivas foram obtidas entre: 1) escala de esforço e apetite por laticínios pós-treino (r = 0,63, p &lt; 0,05); 2) percentual de redução de massa corporal e fome pós-treino (r = 0,55, p &lt; 0,05) e, 3) percentual de redução de massa corporal e apetite por salgados pós-treino (r = 0,59, p &lt; 0,05). Foi possível concluir que a taxa de sudorese média representou um quadro de desidratação moderado ao longo de uma sessão de treino de judô e que alterações no estado de hidratação podem estar associadas com modificações da percepção subjetiva de fome e apetite por determinados alimentos.

Protection of total body water content and absence of hyperthermia despite 2% body mass loss (‘voluntary dehydration’) in soldiers drinking ad libitum during prolonged exercise in cool environmental conditions

The extent to which humans need to replace fluid losses during exercise remains contentious despite years of focused research. The primary objective was to evaluate ad libitum drinking on hydration...