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1.
Personalized fluid and fuel intake for performance optimization in the heat.
Cheuvront, SN, Kenefick, RW
Journal of science and medicine in sport. 2021;(8):735-738
Abstract
It is well appreciated that a loss of body water (dehydration) can impair endurance performance and that the effect is magnified by environmental heat stress. A majority of professional sports medicine and nutrition organizations recommend drinking during exercise to replace sweat losses and prevent dehydration, while also avoiding frank over-hydration. Knowledge of sweating rate, which is highest in the heat for any given metabolic rate, is therefore considered key to developing a sound drinking strategy. Exercise duration and the provision of liquid fuel interacts with required drink volumes in important ways that are infrequently discussed but are of utmost practical concern. This review details some challenges related to the optimized coupling of fluid and fuel needs during prolonged exercise in the heat and the need for personalization.
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2.
Does Hydration Status Influence Executive Function? A Systematic Review.
Katz, B, Airaghi, K, Davy, B
Journal of the Academy of Nutrition and Dietetics. 2021;(7):1284-1305.e1
Abstract
BACKGROUND Cognitive function, including executive function (EF)-related capacities (eg, working memory, inhibitory and attentional control), has been linked to adherence to healthy lifestyle behaviors. Dehydration is associated with impaired cognitive function, whereas improvements in hydration status may improve inhibitory and attentional performance. No systematic reviews have examined the effects of both dehydration and euhydration on EF. OBJECTIVE The objectives of this systematic review are to examine studies that have investigated the spectrum of hydration status and EF in adults, and to identify future research needs. DESIGN The review was conducted according to the 2015 Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) guidelines. The database search was initially conducted on May 12, 2019 and then updated on April 26, 2020. Databases searched included PubMed, Medline, Psyc Info, SCOPUS, Proquest, and ISI Web of Science. Data extraction included the following: method used to assess de/hydration status, study design, participant characteristics, EF tasks and domain, and results. Article quality ratings were performed on included studies using the Academy of Nutrition and Dietetics Quality Rating Checklist. PARTICIPANTS/SETTING Studies done with healthy or diseased adults, aged older than 18 years, in any setting, were included. Studies of individuals with disease states that impact fluid balance or require fluid restrictions as treatments were excluded. MAIN OUTCOME MEASURE All EF-related outcomes were included, such as working memory, inhibitory control, task switching, and attention. RESULTS Four thousand eight hundred thirty-three articles were screened using title/abstracts. Seventy-one full-text articles were assessed for eligibility; 33 were included (26 included investigations of dehydration; 27 included investigations of rehydration/euhydration) with 3,636 participants across all studies. Little consistency was found across outcomes. Roughly half of the available studies suggested unclear or neutral EF effects, and half suggested effects on EF domains, particularly working memory, inhibitory control, and attention. Studies including a euhydration condition were slightly more likely to demonstrate improvements to EF capacities. CONCLUSIONS Overall, there is a strong need for consistent methodological approaches and a greater number of long-term (ie, >3 days) studies of dehydration and euhydration and EF.
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3.
The impact of stress combination on reproductive processes in crops.
Sinha, R, Fritschi, FB, Zandalinas, SI, Mittler, R
Plant science : an international journal of experimental plant biology. 2021;:111007
Abstract
Historically, extended droughts combined with heat waves caused severe reductions in crop yields estimated at billions of dollars annually. Because global warming and climate change are driving an increase in the frequency and intensity of combined water-deficit and heat stress episodes, understanding how these episodes impact yield is critical for our efforts to develop climate change-resilient crops. Recent studies demonstrated that a combination of water-deficit and heat stress exacerbates the impacts of water-deficit or heat stress on reproductive processes of different cereals and legumes, directly impacting grain production. These studies identified several different mechanisms potentially underlying the effects of stress combination on anthers, pollen, and stigma development and function, as well as fertilization. Here we review some of these findings focusing on unbalanced reactive oxygen accumulation, altered sugar concentrations, and conflicting functions of different hormones, as contributing to the reduction in yield during a combination of water-deficit and heat stress. Future studies focused on the effects of water-deficit and heat stress combination on reproduction of different crops are likely to unravel additional mechanisms, as well as reveal novel ways to develop stress combination-resilient crops. These could mitigate some of the potentially devastating impacts of this stress combination on agriculture.
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4.
Palatable Flavoured Fluids without Carbohydrates and Electrolytes Do Not Enhance Voluntary Fluid Consumption in Male Collegiate Basketball Players in the Heat.
Taim, BC, Suppiah, HT, Wee, J, Lee, M, Lee, JKW, Chia, M
Nutrients. 2021;(12)
Abstract
Using palatable fluids to enhance drinking in athletes who display insufficient compensatory hydration behaviour may mitigate the risks of hypohydration and performance deficits. However, it is unclear whether flavour can independently enhance fluid consumption. This study examined the effects of a colourless, artificially sweetened flavoured water (FW), without carbohydrates and with negligible amounts of sodium, compared to plain water (W) on fluid consumption in male collegiate basketball players in a practical game setting. Eighteen male basketball players (age 23.1 ± 1.3 years) played a 3v3 basketball small-sided game. The players were randomly assigned to consume either FW or W. Pre-game urine-specific gravity, fluid consumption, body mass, and hedonic taste perceptions were assessed. Basketball performance was analysed through notational analysis. Ratings of perceived exertion and thirst were recorded at pre-, post-game, and at each rest period. Heart rate was recorded throughout the gameplay. Despite significantly higher hedonic ratings for FW than W (6.78 ± 0.83 vs. 5.56 ± 1.33, p = 0.033, d = 1.36), there were no significant differences in fluid consumption (1083 ± 32 mL vs. 1421 ± 403 mL, p = 0.068, d = 0.92). Our result highlighted that using palatable fluids as a strategy to increase fluid consumption during high-intensity gameplay in the heat may not be effective if used without carbohydrates and electrolytes. Practitioners could consider both fluid palatability and composition in establishing a hydration plan for athletes.
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5.
To hydrate or not to hydrate? The effect of hydration on survival, symptoms and quality of dying among terminally ill cancer patients.
Wu, CY, Chen, PJ, Ho, TL, Lin, WY, Cheng, SY
BMC palliative care. 2021;(1):13
Abstract
BACKGROUND Artificial nutrition and hydration do not prolong survival or improve clinical symptoms of terminally ill cancer patients. Nonetheless, little is known about the effect of artificial hydration (AH) alone on patients' survival, symptoms or quality of dying. This study explored the relationship between AH and survival, symptoms and quality of dying among terminally ill cancer patients. METHODS A pilot prospective, observational study was conducted in the palliative care units of three tertiary hospitals in Taiwan between October 2016 and December 2017. A total of 100 patients were included and classified into the hydration and non-hydration group using 400 mL of fluid per day as the cut-off point. The quality of dying was measured by the Good Death Scale (GDS). Multivariate analyses using Cox's proportional hazards model were used to assess the survival status of patients, the Wilcoxon rank-sum test for within-group analyses and the Mann-Whitney U test for between-groups analyses to evaluate changes in symptoms between day 0 and 7 in both groups. Logistic regression analysis was used to assess the predictors of a good death. RESULTS There were no differences in survival (p = 0.337) or symptom improvement between the hydration and non-hydration group, however, patients with AH had higher GDS scores. CONCLUSIONS AH did not prolong survival nor significantly improve dehydration symptoms of terminally ill cancer patients but it may influence the quality of dying. Communication with patients and their families on the effect of AH may help them better prepared for the end-of-life experience.
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Effects of a 14-Day Hydration Intervention on Individuals with Habitually Low Fluid Intake.
Caldwell, AR, Rosa-Caldwell, ME, Keeter, C, Johnson, EC, Péronnet, F, Ganio, MS
Annals of nutrition & metabolism. 2020;:67-68
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Abstract
BACKGROUND Debate continues over whether or not individuals with low total water intake (TWI) are in a chronic fluid deficit (i.e., low total body water) [1]. When women with habitually low TWI (1.6 ± 0.5 L/day) increased their fluid intake (3.5 ± 0.1 L/day) for 4 days 24-h urine osmolality decreased, but there was no change in body weight, a proxy for total body water (TBW) [2]. In a small (n = 5) study of adult men, there were no observable changes in TBW, as measured by bioelectrical impedance, after increasing TWI for 4 weeks [3]. However, body weight increased and salivary osmolality decreased indicating that the study may have been underpowered to detect changes in TBW. Further, no studies to date have measured changes in blood volume (BV) when TWI is increased. OBJECTIVES Therefore, the purpose of this study was to identify individuals with habitually low fluid intake and determine if increasing TWI, for 14 days, resulted in changes in TBW or BV. METHODS In order to identify individuals with low TWI, 889 healthy adults were screened. Participants with a self-reported TWI less than 1.8 L/day (men) or 1.2 L/day (women), and a 24-h urine osmolality greater than 800 mOsm were included in the intervention phase of the study. For the intervention phase, 15 participants were assigned to the experimental group and 8 participants were assigned to the control group. The intervention period lasted for 14 days and consisted of 2 visits to our laboratory: one before the intervention (baseline) and 14 days into the intervention (14-day follow-up). At these visits, BV was measured using a CO-rebreathe procedure and deuterium oxide (D2O) was administered to measure TBW. Urine samples were collected immediately prior, and 3-8 h after the D2O dose to allow for equilibration. Prior to each visit, participants collected 24-h urine to measure 24-h hydration status. After the baseline visit, the experimental group increased their TWI to 3.7 L for males and 2.7 L for females in order to meet the current Institute of Medicine recommendations for TWI. RESULTS Twenty-four-hour urine osmolality decreased (-438.7 ± 362.1 mOsm; p < 0.001) and urine volume increased (1,526 ± 869 mL; p < 0.001) in the experimental group from baseline, while there were no differences in osmolality (-74.7 ± 572 mOsm; p = 0.45), or urine volume (-32 ± 1,376 mL; p = 0.89) in the control group. However, there were no changes in BV (Fig. 1a) or changes in TBW (Fig. 1b) in either group. CONCLUSIONS Increasing fluid intake in individuals with habitually low TWI increases 24-h urine volume and decreases urine osmolality but does not result in changes in TBW or BV. These findings are in agreement with previous work indicating that TWI interventions lasting 3 days [2] to 4 weeks [3] do not result in changes in TBW. Current evidence would suggest that the benefits of increasing TWI are not related changes in TBW.
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Subcutaneous hydration and medications infusions (effectiveness, safety, acceptability): A systematic review of systematic reviews.
Broadhurst, D, Cooke, M, Sriram, D, Gray, B
PloS one. 2020;(8):e0237572
Abstract
OBJECTIVE To synthesize the current evidence for subcutaneous hydration and medication infusions from systematic reviews and to assess their methodological quality. INTRODUCTION Peripheral intravascular cannula/catheter insertion is a common invasive procedure for administering fluids and medications. Venous depletion is a growing concern for several patient populations. Subcutaneous access for the administration of isotonic solutions and medications is an alternative; however, vascular access assessment and planning guidelines rarely consider this route. METHODS Systematic review of systematic reviews (PROSPERO CRD42018046504). We searched 6 databases published in English language from 1990 to June 2020, identifying subcutaneous infusions an alternate route for fluids or medication. Methodological quality was evaluated using AMSTAR 2 criteria and data for mechanisms of infusion and outcomes related to effectiveness, safety, efficiency and acceptability extracted. The Johanna Briggs Institute's grades of recommendation informed the strength of recommendation. RESULTS The search yielded 1042 potential systematic reviews; 922 were excluded through abstract and duplicate screen. Of the remaining articles, 94 were excluded, and 26 were included. Overall, evidence is strong for recommending subcutaneous hydration infusions for older adults, weak for pediatric patients and inconclusive for palliative patients. There is strong evidence for 10 medications; weak evidence supporting 28 medications; however, there are eight medications with inconclusive evidence to make a recommendation and four medications not appropriate for subcutaneous delivery. CONCLUSION Subcutaneous access should be considered alongside intravenous therapy for hydration in older adults, and several medications. There are additional benefits in terms of ease of use and cost-effectiveness of this mode. Inclusion of subcutaneous access in clinical guidelines may promote uptake of this route to help preserve vessel health of vulnerable patients. Further high-quality research is needed to inform subcutaneous infusion therapy in a variety of populations (including pediatrics and palliative care) and medications and clarifying the mechanism of delivery.
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Up in the Air: Evidence of Dehydration Risk and Long-Haul Flight on Athletic Performance.
Zubac, D, Buoite Stella, A, Morrison, SA
Nutrients. 2020;(9)
Abstract
The microclimate of an airline cabin consists of dry, recirculated, and cool air, which is maintained at lower pressure than that found at sea level. Being exposed to this distinctive, encapsulated environment for prolonged durations, together with the short-term chair-rest immobilization that occurs during long-haul flights, can trigger distinct and detrimental reactions to the human body. There is evidence that long-haul flights promote fluid shifts to the lower extremity and induce changes in blood viscosity which may accelerate dehydration, possibly compromising an athlete's potential for success upon arrival at their destination. Surprisingly, and despite several recent systematic reviews investigating the effects of jet lag and transmeridian travel on human physiology, there has been no systematic effort to address to what extent hypohydration is a (health, performance) risk to travelers embarking on long journeys. This narrative review summarizes the rationale and evidence for why the combination of fluid balance and long-haul flight remains a critically overlooked issue for traveling persons, be it for health, leisure, business, or in a sporting context. Upon review, there are few studies which have been conducted on actual traveling athletes, and those that have provide no real evidence of how the incidence rate, magnitude, or duration of acute dehydration may affect the general health or performance of elite athletes.
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The Influence of Heat Acclimation and Hypohydration on Post-Weight-Loss Exercise Performance.
Barley, OR, Chapman, DW, Mavropalias, G, Abbiss, CR
International journal of sports physiology and performance. 2020;(2):213-221
Abstract
PURPOSE To examine the influence of fluid intake on heat acclimation and the subsequent effects on exercise performance following acute hypohydration. METHODS Participants were randomly assigned to 1 of 2 groups, either able to consume water ad libitum (n = 10; age 23 [3] y, height 1.81 [0.09] m, body mass 87 [13] kg; HAW) or not allowed fluid (n = 10; age 26 [5] y, height 1.76 [0.05] m, body mass 79 [10] kg; HANW) throughout 12 × 1.5-h passive heat-acclimation sessions. Experimental trials were completed on 2 occasions before (2 baseline trials) and 1 following the heat-acclimation sessions. These sessions involved 3 h of passive heating (45°C, 38% relative humidity) to induce hypohydration followed by 3 h of ad libitum food and fluid intake after which participants performed a repeat sled-push test to assess physical performance. Urine and blood samples were collected before, immediately, and 3 h following hypohydration to assess hydration status. Mood was also assessed at the same time points. RESULTS No meaningful differences in physiological or performance variables were observed between HANW and HAW at any time point. Using pooled data, mean sprint speed was significantly (P < .001) faster following heat acclimation (4.6 [0.7] s compared with 5.1 [0.8] s). Furthermore, heat acclimation appeared to improve mood following hypohydration. CONCLUSIONS Results suggest that passive heat-acclimation protocols may be effective at improving short-duration repeat-effort performance following acute hypohydration.
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10.
Mild dehydration impaired intermittent sprint performance and thermoregulation in females.
Driscoll, RL, McCarthy, DG, Palmer, MS, Spriet, LL
Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme. 2020;(9):1045-1048
Abstract
The effects of mild dehydration during ice hockey are well-studied in males but not females. In a randomized, crossover design, 11 female varsity hockey players drank no fluid (1.7% ± 0.3% body mass loss) or water to maintain hydration during simulated-hockey exercise. Core temperature (P < 0.01) and perceived fatigue (P = 0.02) were higher and sprint power lower (P < 0.01) when mildly dehydrated. Thus, mild dehydration may impair hockey performance and thermoregulation while increasing perceived fatigue in females. Novelty Female stop-and-go sport athletes may benefit their in-game sprint performance and thermoregulation by following personalized in-game hydration to prevent becoming mildly dehydrated.