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Alan J. McCubbin, Bethanie A. Allanson, Joanne N. Caldwell Odgers, Michelle M. Cort, Ricardo J.S. Costa, Gregory R. Cox, Siobhan T. Crawshay, Ben Desbrow, Eliza G. Freney, Stephanie K. Gaskell, David Hughes, Chris Irwin, Ollie Jay, Benita J. Lalor, Megan L.R. Ross, Gregory Shaw, Julien D. Périard, and Louise M. Burke

). These two terms are often used interchangeably as they both induce physiological adaptations that can benefit athletic performance during prolonged events ( Périard et al., 2015 ). Initial adaptations, including plasma volume ( P v ) expansion, enhanced fluid balance, reduced heart rate, and decreased

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Craig A. Horswill

As a result of exercise-induced sweating, athletes and trained individuals can lose up to 3 L of fluid per hour. Fluid replacement is required to maintain hydration and allow the athlete to continue to perform. Inadequate fluid intake will adversely affect temperature regulation, cardiovascular function, and muscle metabolism. To maximize fluid intake and effectively replace fluid, athletes must employ behavioral strategies. Athletes can also select beverages with characteristics that complement their behavioral efforts. Palatability, rapid absorption, retention of the fluid, and ergogenicity are the major attributes to consider for enhancing hydration during training and physical activity.

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Paola Rodriguez-Giustiniani and Stuart D.R. Galloway

Maintenance of fluid balance is a major consideration for recreational exercisers and athletes ( Maughan et al., 1997 ). As hypohydration, defined as the uncompensated loss of body water, is known to influence exercise performance and health ( Evans et al., 2017 ), starting exercise in a euhydrated

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Beat Knechtle, Patrizia Knechtle, and Thomas Rosemann


Fluid overload is considered a main risk factor for exercise-associated hyponatremia (EAH). The aim of this study was to investigate the incidence of EAH in ultra-runners at the 100 km ultra-run in Biel, Switzerland.


Pre- and postrace, body mass, urinary specific gravity, hemoglobin, hematocrit, plasma [Na+], and plasma volume were determined.


Of the 145 finishers, seven runners (4.8%) developed asymptomatic EAH. While running, the athletes consumed a total of (median and interquartile ranges) 6.9 (5.1-8.8) L over the 100 km distance, equal to 0.58 (0.41-0.79) L/h. Fluid intake correlated negatively and significantly with race time (r = -.50, P < .0001). Body mass decreased, plasma [Na+] remained unchanged, hematocrit and hemoglobin decreased, and urinary specific gravity increased. Plasma volume increased by 4.6 (-2.3 to 12.8) %. Change in body mass correlated with both postrace plasma [Na+] and Δ plasma [Na+]. Postrace plasma [Na+] correlated to Δ plasma [Na+]. Fluid intake was associated neither with postrace plasma [Na+] nor with Δ plasma [Na+]. Fluid intake was related to Δ body mass (r = .21, P = .012), but not to postrace body mass. Fluid intake showed no correlation to Δ plasma volume. Change in plasma volume was associated with postrace [Na+].


Incidences of EAH in 100 km ultra-marathoners were lower compared with reports on marathoners. Body mass decreased, plasma volume increased, and plasma [Na+] was maintained. Since fluid intake was related neither to Δ plasma volume nor to Δ plasma [Na+], we assume that factors other than fluid intake maintained body fluid homeostasis.

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Eric D.B. Goulet, Adrien De La Flore, Félix A. Savoie, and Jonathan Gosselin

 al., 2009 ), decrease the risk of decompression sickness in divers ( Gempp et al., 2009 ), and when used on a day-to-day basis, slow or neutralize bone density loss in hypokinetic subjects ( Zorbas et al., 1991 ). An optimal hyperhydration solution should be rapidly integrated into the body fluid pool

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Reid Reale, Gary Slater, Gregory R. Cox, Ian C. Dunican, and Louise M. Burke

-in. Common and effective methods include active and passive sweating; diuretics; fluid and sodium restriction (reducing body water) and reduction of gut contents via laxative use, fasting, reducing food volume; and reduced carbohydrate and/or fiber intake ( Franchini et al., 2012 ; Reale et al., 2016

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Jennifer L. Etnier and Daniel M. Landers

The primary purpose of this study was to examine differences in performance on fluid and crystallized intelligence tasks as a function of age and fitness. A secondary purpose was to examine the influence of age and fitness on the beneficial effects that practice has on both performance and retention on these tasks. Fitness was assessed in 41 older and 42 younger participants who were then randomly assigned to either experimental or control conditions. Participants performed repeated trials on two cognitive tasks during acquisition and retention, with the experimental group practicing for 100 trials and the control group practicing for 20 trials. Older participants performed better than younger participants on the crystallized intelligence task: however, younger participants performed better than older participants on the fluid intelligence task. On the fluid intelligence task, older fit participants performed better than older unfit participants. Learning did occur on the fluid task and differed as a function of age and fitness. Learning did not occur on the crystallized task.

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Stefan Pettersson and Christina M. Berg

Weight category athletes are known for practicing rapid weight loss before competition weigh-in. After weigh-in, athletes strive to restore euhydration and body mass through food and fluid intake. The aim of the current study was to assess prevalence of hypohydration at competition time among elite athletes’ in four different combat sports, and how water intake and timing of official weigh-in were related to hydration status. Participants were 31 taekwondo practitioners and wrestlers who performed evening weigh-in (EWI) the night before competition day and had thus time for rehydration, and 32 boxers and judokas conducting competition day morning weigh-in (MWI). In total, 32% were female. Urine specific gravity (USG) was measured by refractometry on the competition day’s first morning urine sample. Hypohydration was defined as USG ≥1.020 and serious hypohydration as USG > 1.030. Water intake was measured by means of dietary records. The prevalence of hypohydration was 89% in the morning of competition day. Serious hypohydration was also prevalent. This was found in over 50% of MWI athletes and in 42% of the EWI group. A higher water intake, from both fluids and solid foods, in the evening before competition day was not associated with a more favorable hydration status the following morning. In conclusion, neither weigh-in close to competition nor evening weigh-in with more time for rehydration seems to prevent hypohydration before competition.

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Eric Kyle O’Neal, Samantha Louise Johnson, Brett Alan Davis, Veronika Pribyslavska, and Mary Caitlin Stevenson-Wilcoxson

 al., 2000 ; Convertino et al., 1996 ; McDermott et al., 2017 ; Sawka et al., 2007 ) and opposing viewpoints concerning these guidelines ( Beltrami et al., 2008 ; Hew-Butler et al., 2005 ). Sweat loss volume must first be established if prescribed fluid intake is to be incorporated before, during, or

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Ben Desbrow, Katelyn Barnes, Gregory R. Cox, Elizaveta Iudakhina, Danielle McCartney, Sierra Skepper, Caroline Young, and Chris Irwin

Postexercise “recovery stations” (where food and fluid are available) are a common feature of developed sports programs for athletes and routinely organized for mass participation events (e.g., fun runs, marathons, triathlons). While these are often critical to promote recovery for individuals