Hydration

Introducción: Durante el ejercicio, el trabajo muscular es el mayor generador de calor, el cual es disipado principalmente por evaporación de sudor generando una deshidratación potencialmente perjudicial para el rendimiento.
Objetivos: Establecer la tasa de sudoración y el nivel de hidratación pre y post-entrenamiento, de jugadores de básquetbol de LNB (Chile), pertenecientes al Club Deportivo Universidad Católica.
Métodos: 15 jugadores (26,3 ± 4,4 años, 87,8 ± 12,2 kg) fueron controlados durante un entrenamiento de musculación seguido de baloncesto. Antes de la musculación, antes del baloncesto y al terminar, gravedad específica de orina (GEO) y peso fueron controlados. Durante el entrenamiento se controló ingesta de agua y volumen de orina.
Resultados: Sólo 2/15 jugadores llegaron a la práctica bien hidratados o con deshidratación mínima (GEO PRE = 1,026 ± 0,008). Al finalizar, según la pérdida de peso relativa, 6 jugadores están bien hidratados y 9 con deshidratación mínima (PP REL = 1,15 ± 0,58) y según GEO, 4 están bien hidratados o con deshidratación mínima y 10 tienen deshidratación significativa o seria (GEO POST = 1,025 ± 0,010). La tasa de sudoración (sólo baloncesto) es de 946 ± 340 ml/hora. Conclusiones: Los jugadores llegan deshidratados a la práctica y muestran pérdidas de peso moderadas durante ella. Los valores GEO POST muestran una mejora en el nivel de hidratación durante la práctica, por lo que GEO no sería adecuada para controlar el nivel de deshidratación post-entrenamiento. Finalmente, se recomienda usar una tasa de sudoración de 1,0 l/h para establecer estrategias de hidratación.

Гидратация ионов в водных растворах солей KOH, KCl, KI и KIO3 была исследована рефрактометрическим методом. Сумма чисел гидратации иона калия и каждого аниона в указанных соединениях, а также числа гидратации анионов OH–, Cl–, I– и IO определены на основе уравнения Лоренца–Лоренца при различных концентрациях солей. В предложенной модели предположено что, поляризуемость гидратированного иона пропорциональна кубу радиуса этого иона, а объем гидратированного иона равен сумме объема негидратированного иона и объема гидратной оболочки. Установлено, что вычисленные предложенным методом числа гидратации анионов увеличиваются с ростом
их радиусов в следующем порядке: OH–, Cl–, I– и IO .

In this study, Portland/calcium aluminate blended cement (PC/CAC) was combined with citric acid or lactic acid as additives to investigate the effects of the aforementioned carboxylic acids on the hydration reactions of PC/CAC as a potential fast hardening and low cost repair material for concrete. Mortar specimens with the carboxylic acid additives of either 0.5%, 1% or 3% by weight, prepared with a binder:sand:water ratio (by weight) of 1:3:0.5, were subjected to flexural and compressive strength tests at early ages up to 28 days. In order to understand the phase composition of the hydrates in the PC/CAC systems, XRD analyses were conducted on ground PC/CAC mortars with and without carboxylic acid at 7, 14 and 28 days. In combination with this, SEM images of selected mortar specimens were also taken at the same times for visual analyses of hydrates. Citric acid did not have any beneficial effect on enhancing the calcium silicate phase as initially assumed and instead reduced the strength of PC/CAC cement at all levels of concentration. The experiment analyses revealed that Portlandite crystals were the major hydrate phase in PC/CAC with lactic and citric acids. Lactic acid below 2% wt. improved both compressive and flexural strength gained at early ages due to improved crystallinity of the calcium hydroxide crystals. Combined with its inherent rapid setting time, PC/CAC blended cements have a potential to be developed into a suitable repair material for concrete.

— The aim of the present work is to study the effect of low grade aluminosilicate refractory bricks (ASRBs) with metakaolin (MK) on the hydration properties and the fire resistance of composite cement pastes at elevated temperature up to 800 o C. The composite cement are composed of constant proportion of ordinary Portland cement (OPC) (80 wt%) with variable amounts of ASRBs and MK. The substitution of 20% ASRBs with MK increases the water of consistency and retarded the initial as well as the final setting times, whereas the free lime contents and the bulk density decreases with MK. The compressive strength increases with MK content which enhanced the early and long term strength. It acts also as micro-filler that accelerates initial cement hydration. The fire resistance of composite cement pastes was evaluated up to 800 o C with rate of firing 5 o C/min. and soaking time for 2 h. The physico-mechanical properties such as, weight loss, bulk density and compressive strength were determined at each firing temperature. Moreover, some selected samples were investigated by using XRD, DTA/TG and SEM techniques analyses. Cement pastes containing 20 wt% ASRBs (PC-A) is the optimum composite cement paste which gives high bulk density and compressive strength. It can be concluded the cement paste PC-A has a good fire resistance paste.

Water is an essential nutrient for all physiological functions and particularly important for thermoregulation. About 60% of our body weight is made of water. Under standard conditions (18–20 ° C and moderate activity), water balance is regulated within 0.2 % of body weight over a 24-hour period. Water requirement varies between individuals and according to
environmental conditions. Concerning considerations related to obesity, the health impact of fluid intake is commonly overlooked. Fluid intake advices are missing in most of food pyramids offered to the public, and water requirements and hydration challenges remain often neglected.
The purpose of this paper is to emphasize and discuss the role of water consumption in the context of other important public health measures for weight management. Attention will be
focused on fluid intake patterns and hydration-related questions in the context of global interventions and/or physical activity programs settled in weight management protocols.

Background: Information about behavior of energy intake in ultra-endurance cyclists during a 24-hour team relay race is scarce. The nutritional strategy during such an event is an important factor which athletes should plan carefully before the race. The purpose of this study was to examine and compare the nutritional intake of ultraendurance
cyclists during a 24-hour team relay race with the current nutritional guidelines for endurance events.
Additionally, we analyzed the relationship among the nutritional and performance variables.
Methods: Using a observational design, nutritional intake of eight males (mean ± SD: 36.7 ± 4.7 years; 71.6 ± 4.9
kg; 174.6 ± 7.3 cm; BMI 23.5 ± 0.5 kg/m2) participating in a 24-hour team relay cycling race was assessed. All food and fluid intake by athletes were weighed and recorded. Additionally, distance and speed performed by each rider were also recorded. Furthermore, before to the race, all subjects carried out an incremental exercise test to determine two heart rate-VO2 regression equations which were used to estimate the energy expenditure.
Results: The mean ingestion of macronutrients during the event was 943 ± 245 g (13.1 ± 4.0 g/kg) of carbohydrates, 174 ± 146 g (2.4 ± 1.9 g/kg) of proteins and 107 ± 56 g (1.5 ± 0.7 g/kg) of lipids, respectively. This amount of nutrients reported an average nutrient intake of 22.8 ± 8.9 MJ which were significantly lower compared with energy expenditure 42.9 ± 6.8 MJ (P = 0.012). Average fluid consumption corresponded to 10497 ± 2654 mL.
Mean caffeine ingestion was 142 ± 76 mg. Additionally, there was no relationship between the main nutritional variables (i.e. energy intake, carbohydrates, proteins, fluids and caffeine ingestion) and the main performance variables (i.e. distance and speed).
Conclusions: A 24-hour hours cycling competition in a team relay format elicited high energy demands which were not compensated by energy intake of the athletes despite that dietary consumption of macronutrients did not differ to the nutritional guidelines for longer events.

Among athletes, endurance is one of the key elements to victory. In addition to training, athletes normally used supplement to prevent fatigue during the event. With prolonged and intense activity, our body started to experience decrease in muscle performance due to several factors such as oxidative stress, dehydration and accumulation of lactic acid in the body fluids. The free radicals generated during intense exercise will expose the cells to oxidative damages. In the event of dehydration, there will be significant losses of water and functional electrolytes during intense exercise which affected the body fluid balance. Fatigue will also occur during reduced oxygen in aerobic metabolism which later caused accumulation of lactic acid in the muscle. This will change the pH balance toward more acidic and caused the muscles to lose contractile efficiency. In addition, fatigue can also be studied using rats as model organism. Results from this activity can be useful to analyse cellular metabolism and physiology effects of the tested rats toward physical exercise. Therefore, this review aims to discuss the causes of fatigue through oxidative stress, dehydration and lactic acid accumulation. In addition, the effectiveness of using rats as a model system in measuring fatigue is also included in illustrating examples on fatigue assessment in vivo.

INTRODUCTION:
The National Institute of Child Health and Human Development, American College of Obstetricians and Gynecologists, and Society for Maternal-Fetal Medicine have emphasized the need to promote vaginal delivery and have offered recommendations to safely prevent primary cesarean delivery. However, there has been limited discussion regarding management of intravenous fluids and other aspects of labor management that may influence labor. Therefore the aim of our study was to determine if an intravenous fluid rate of 250 vs 125 mL/hour is associated with a difference in cesarean delivery rate MATERIAL AND METHODS: Searches were performed in Medline, OVID, Scopus, ClinicalTrials. gov, the PROSPERO International Prospective Register of Systematic Reviews, Embase, Web of Science, and the Cochrane Library for randomized controlled trials. We included all randomized controlled trials comparing intravenous fluid rates of 125 mL/hour vs. 250 mL/hour in nulliparous women in spontaneous labor at term with singleton pregnancies at ≥ 36 weeks. Studies were included regardless of the type of intravenous fluids used and regardless of whether or not oral intake was restricted during labor. Studies including multiparous women or women whose labor was induced were excluded. The primary outcome was the incidence of cesarean delivery. We planned to assess a sensitivity analysis according to type of fluids used and according to restriction of oral fluid intake RESULTS: Seven trials including 1,215 nulliparous women in spontaneous labor at term were analyzed. 593 (48.8%) were in the 250 mL/hour group, and 622 (51.2%) in the 125 mL/hour group. Five studies used lactated Ringer's solution, one used normal saline in dextrose water, and in one study it was unclear which intravenous fluid was used. Women who received intravenous fluids 250 mL/hour had a significantly lower incidence of cesarean delivery for any indication (12.5% vs 18.1%; RR 0.70, 95% CI 0.53 to 0.92; 7 studies, 1,215 participants; I2 =0%) and for dystocia (4.9% vs 7.7%; RR 0.60, 95% CI 0.38 to 0.97; 5 studies, 1,093 participants; I2 =18%) and a significantly shorter mean of duration of labor of about one hour (mean difference -64.38 minutes, 95% CI -121.88 to -6.88; 6 studies, 1,155 participants; I2 =83%) and of length of second stage of labor (mean difference -2.80 minutes, 95% CI -4.49 to -1.10; 899 participants; I2 =22%) compared to those who received intravenous fluid 125 mL/hour. No differences were found in the other secondary outcomes. There were no maternal or perinatal deaths and only one woman, in the 125 ml/hr group, developed pulmonary edema. The findings persisted regardless of the type of intravenous fluid used. No significant reduction in the incidence of cesarean delivery was demonstrated in women with unrestricted oral intake; however, this was limited to only 2 studies evaluating 254 women CONCLUSIONS: In conclusion, our findings provide evidence that the duration of labor in low-risk nulliparous women may be shortened by a policy of intravenous fluids at a rate of 250 mL/hours rather than 125 mL/hours. This could also lead to a reduction in the incidence of cesarean delivery. The number needed to treat to prevent one cesarean delivery is 18 women. Our data support for increased hydration amongst nulliparous women in labor when oral intake is restricted. Further study is needed regarding risks and benefits of increased hydration among women with unrestricted oral intake, those undergoing induction of labor, and those with medical comorbidities.

In this work a coupled thermo-chemo-mechanical model for the behavior of concrete at early ages is proposed. The model allows simulation of the observed phenomena of hydration, aging, damage, and creep. It is formulated within an appropriate thermodynamic framework, from which the state equations are derived. In this first part, the formulation and assessment of the thermochemical aspects of the model are presented. It is based on the reactive porous media theory, and it can accurately predict the evolution in time of the hydration degree and the hydration heat production. The evolution of the compressive and tensile strengths and elastic moduli is related to the aging degree, a concept introduced to account for the effect of the curing temperature in the evolution of the mechanical properties. The short-and long-term mechanical behavior is modeled by means of a viscoelastic damage model that accounts for the aging effects. The formulation and assessment of the mechanical part of the model are relegated to a companion paper.