Ad libitum adjustments to fluid intake during cool environmental conditions maintain hydration status during a 3-day mountain bike race

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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Development of Individual Hydration Strategies for Athletes

International Journal of Sport Nutrition and Exercise Metabolism ◽

10.1123/ijsnem.18.5.457 ◽

2008 ◽

Vol 18 (5) ◽

pp. 457-472 ◽

Cited By ~ 81

Author(s):

Ronald J. Maughan ◽

Susan M. Shirreffs

Keyword(s):

Specific Gravity ◽

Body Mass ◽

Environmental Conditions ◽

Fluid Intake ◽

Sweat Rate ◽

Hydration Status ◽

Additional Information ◽

Urine Color ◽

Individual Needs ◽

Exercise Environment

Athletes are encouraged to begin exercise well hydrated and to consume sufficient amounts of appropriate fluids during exercise to limit water and salt deficits. Available evidence suggests that many athletes begin exercise already dehydrated to some degree, and although most fail to drink enough to match sweat losses, some drink too much and a few develop hyponatremia. Some simple advice can help athletes assess their hydration status and develop a personalized hydration strategy that takes account of exercise, environment, and individual needs. Preexercise hydration status can be assessed from urine frequency and volume, with additional information from urine color, specific gravity, or osmolality. Change in hydration during exercise can be estimated from the change in body mass that occurs during a bout of exercise. Sweat rate can be estimated if fluid intake and urinary losses are also measured. Sweat salt losses can be determined by collection and analysis of sweat samples, but athletes losing large amounts of salt are likely to be aware of the taste of salt in sweat and the development of salt crusts on skin and clothing where sweat has evaporated. An appropriate drinking strategy will take account of preexercise hydration status and of fluid, electrolyte, and substrate needs before, during, and after a period of exercise. Strategies will vary greatly between individuals and will also be influenced by environmental conditions, competition regulations, and other factors.

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Reliability of Urinary Dehydration Markers in Elite Youth Boxers

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2016-0621 ◽

2018 ◽

Vol 13 (3) ◽

pp. 374-381 ◽

Cited By ~ 3

Author(s):

Damir Zubac ◽

Drazen Cular ◽

Uros Marusic

Keyword(s):

Body Weight ◽

Actual Body ◽

Body Mass ◽

Fluid Intake ◽

Real Life ◽

Diagnostic Tools ◽

Stable Phase ◽

Hydration Status ◽

Actual Body Weight ◽

Ad Libitum

Purpose:To determine the reliability and diagnostic accuracy of noninvasive urinary dehydration markers in field-based settings on a day-to-day basis in elite adolescent amateur boxers.Methods:Sixty-nine urine samples were collected daily from 23 athletes (17.3 ± 1.9 y) during their weight-stable phase and analyzed by field and laboratory measures of hydration status. Urine osmolality (UOSM), urine specific gravity (USG), total protein content (TPC), and body-mass stability were evaluated to determine fluid balance and hydration status. Overall macronutrient and water intake were determined using dietary records. According to their anthropometric characteristics, athletes were assigned into 2 groups: lightweight (LWB) and heavyweight (HWB) boxers.Results:Data presented on UOSMdemonstrated a uniform increment by 11.2% ± 12.8% (LWB) and 19.9% ± 22.7% (HWB) (P < .001) over the course of the study, even during the weight-stable phase (body mass, ICC = .99) and ad libitum fluid intake (42 ± 4 mL · kg−1 · d−1). The intraclass correlation coefficients (ICCs) ranged from .52 to .55 for USGand .38 to .52 for UOSM, further indicating inconsistency of the urinary dehydration markers. Poor correlations were found between USGand TPCmetabolites (r = .27,P = .211).Conclusions:Urinary dehydration markers (both USGand UOSM) exhibit high variability and seem to be unreliable diagnostic tools to track actual body-weight loss in real-life settings. The ad libitum fluid intake was apparently inadequate to match acute fluid loss during and after intense preparation. The applicability of a single-time-point hydration-status assessment concept may preclude accurate assessment of actual body-weight deficits in youth boxers.

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Hydration Status in Adolescent Alpine Skiers During a Training Camp

Journal of Human Kinetics ◽

10.2478/hukin-2021-0062 ◽

2021 ◽

Vol 79 (1) ◽

pp. 55-63

Author(s):

Dirk Aerenhouts ◽

Laurent Chapelle ◽

Peter Clarys ◽

Evert Zinzen

Keyword(s):

Specific Gravity ◽

Fluid Intake ◽

Training Session ◽

Urine Specific Gravity ◽

Hydration Status ◽

Fluid Loss ◽

Individual Values ◽

Training Camp ◽

Ad Libitum ◽

Alpine Skiers

Abstract Maintaining euhydration is important for optimal health, performance and recovery, but can be challenging for alpine skiers when training in a relatively cold but dry environment. This study aimed to evaluate hydration status, fluid loss and fluid intake in adolescent alpine skiers during a training camp. Twelve athletes aged 14.3 ± 0.9 years volunteered to participate in the study. Athletes resided at an altitude of 1600 m and trained between 1614 and 2164 m. During eight consecutive days, urine specific gravity was measured before each morning training session using a refractometer. Changes in body weight representing fluid loss and ad libitum fluid intake during each morning training session were assessed using a precision scale. Mean pre-training urine specific gravity remained stable throughout the training camp. Individual values ranged between 1.010 and 1.028 g/cm3with 50 to 83% of athletes in a hypohydrated state (urine specific gravity ≥ 1.020 g/cm3). Mean training induced fluid loss remained stable throughout the training camp (range -420 to -587 g) with individual losses up to 1197 g (-3.5%). Fluid intake was significantly lower than fluid loss during each training session. To conclude, urine specific gravity values before training indicated insufficient daily fluid intake in more than half of the athletes. Furthermore, fluid intake during training in adolescent alpine skiers was suboptimal even when drinks were provided ad libitum. Coaches and athletes should be encouraged to carefully monitor hydration status and to ensure that alpine skiers drink sufficiently during and in between training sessions.

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Fluid use in mountain bikers - self-reported practices

South African Journal of Sports Medicine ◽

10.17159/2078-516x/2007/v19i2a266 ◽

2007 ◽

Vol 19 (2) ◽

pp. 52 ◽

Cited By ~ 2

Author(s):

SC Rose ◽

HA Chipps ◽

EM Peters

Keyword(s):

South African ◽

Sports Medicine ◽

Fluid Intake ◽

Endurance Athletes ◽

Fluid Replacement ◽

Hydration Status ◽

Mountain Bike ◽

Usual Intake ◽

Past Experiences ◽

African Journal

Background and objectives. Little is known of the fluid replacement habits of participants in mountain bike (MTB) endurance events. This survey set out to determine the current perceptions and practices of this group of endurance athletes. Method. Four hundred and twelve participants in the 3- day 2006 Sani2C (MTB) race completed questionnaires that elicited information regarding their regular fluid intake practices during competitive MTB endurance events. This included their general approach to fluid replacement, their fluid intake practices (type, amount and frequency), urine output and hydration status. Results. While 70% (N = 290) reported that they based their fluid intake practices on personal past experiences, less than half the group (N = 177, 43%) were aware of official sport-specific guidelines. Although 86% (N = 354) reported making use of commercially available sport-specific drinks, consumption of water alone was reported by 34% of respondents (N = 140). The majority (N = 225, 55%) of the mountain bikers reported drinking every 16 - 30 minutes during an endurance ride, while 35% (N = 144) reported drinking every 0 - 15 minutes. Fifty-three per cent (N = 182) of the male respondents and 45% (N = 23) of female respondents reported a routine intake of ≥ 750 ml per hour during endurance rides. This included 2 women who reported regular intakes of between 1 500 and 2 000 ml/hr. Only 7 (2%) reported receiving medical care for dehydration following their participation in previous MTB rides. Conclusions. This survey indicates that although more than half of the mountain bikers did not acknowledge specific awareness of the official fluid replacement guidelines, over 80% reported drinking regularly during a race, and 52% (N = 212) reported a usual intake of ≥ 750 ml/hr during endurance races. Until scientific studies have carefully examined the hydration status and fluid replacement needs of mountain bikers, MTB cyclists are cautioned against the practice of over-hydrating. South African Journal of Sports Medicine Vol. 19 (2) 2007: pp. 52-58

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Dependence of Urinary Prostaglandin E2 Excretion on Urinary Volume Rather than Solute Handling or Segmental Nephron Function in Man

Clinical Science ◽

10.1042/cs0670413 ◽

1984 ◽

Vol 67 (4) ◽

pp. 413-420 ◽

Cited By ~ 15

Author(s):

Sming Kaojarern ◽

Polavat Chennavasin ◽

Ann Burdette ◽

William B. Campbell ◽

D. Craig Brater

Keyword(s):

Prostaglandin E2 ◽

Sodium Excretion ◽

Fluid Intake ◽

Urinary Sodium Excretion ◽

Urinary Sodium ◽

Urinary Flow ◽

Urinary Volume ◽

Water Loading ◽

Wide Range ◽

Ad Libitum

1. Eight normal subjects underwent water loading alone and water loading plus 40 mg of frusemide IV, fluid intake ad libitum alone and fluid intake ad libitum plus frusemide, plus each of the preceding after pretreatment with indomethacin. 2. After frusemide administration, increases in urinary sodium excretion paralleled increases in urinary volume, and urinary prostaglandin E2 (PGE2) excretion correlated closely with sodium excretion (y = 1.03x −0.28; r = 0.940; P<.0001). 3. In the absence of the diuretic, urinary volume varied over a wide range with little change in sodium excretion. Again, urinary PGE2 excretion correlated with urinary sodium excretion (y = 0.12x + 0.05; r = 0.789; P<.002). However, the correlation differed markedly from that observed in the studies with frusemide. 4. Expressing urinary PGE2 excretion as a function of urinary volume for all of the studies resulted in a highly significant correlation (y = 10.7x −0.70; r = 0.975; P<.0001). 5. Multiple and stepwise regression analyses assessing the correlation of urinary PGE2 excretion with urinary flow rate and with indices of function of various nephron segments indicate that the correlation with urinary PGE2 could be predominantly accounted for by urinary volume. 6. We conclude that in the condition of this study in man, urinary PGE2 excretion is a correlate of urinary volume.

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Effects of the Amount and Frequency of Fluid Intake on Cognitive Performance and Mood among Young Adults in Baoding, Hebei, China: A Randomized Controlled Trial

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17238813 ◽

2020 ◽

Vol 17 (23) ◽

pp. 8813

Author(s):

Hairong He ◽

Jianfen Zhang ◽

Na Zhang ◽

Songming Du ◽

Shufang Liu ◽

...

Keyword(s):

Randomized Controlled Trial ◽

Young Adults ◽

Cognitive Performance ◽

Fluid Intake ◽

Controlled Trial ◽

Urine Osmolality ◽

Memory Test ◽

Hydration Status ◽

Randomized Controlled ◽

Time Point

Water is a critical nutrient that is important for the maintenance of the physiological function of the human body. This article aimed to investigate the effects of the amount and frequency of fluid intake on cognitive performance and mood. A double-blinded randomized controlled trial was designed and implemented on college students aged 18–23 years in Baoding, China. Participants were randomly assigned into one of three groups: the recommended behavior group (RB group) who drank 200 mL of water every 2 h, the half amount group (HA group) who drank 100 mL of water every 2 h, and the high frequency group (HF group) who drank 110 mL of water every 1 h. The intervention lasted 2 days. Urine osmolality, cognitive performance, and mood of participants in each group were compared using the one-way analysis of variance (ANOVA). A total of 92 participants (46 females, 46 males) completed this study with a completion rate of 95.8%. The urine osmolality of the HA group was higher than that of the RB group and the HF group at two time points (p < 0.05). At time point 1, the scores in the portrait memory test and vigor were statistically different (F = 20.45, p < 0.001; F = 5.46, p = 0.006). It was found that the scores for the portrait memory test in the RB group were lower than those in the HA group and the HF group (p = 0.007; p < 0.001), while the scores of the HF group were higher than those of the HA group (p < 0.001). The scores for vigor in the RB group were significantly higher than those of the HA group (p = 0.006), and they were also significantly higher than those of the HF group (p = 0.004). At time point 2, only the scores for vigor were statistically different (F = 3.80, p = 0.026). It was found that the scores for vigor in the RB group were higher than those in the HA group and HF group (p = 0.018; p = 0.019). Both the amount and frequency of fluid intake may affect urine osmolality and vigor, but these factors have limited impacts on cognitive performance. Rational fluid intake behavior may be beneficial to improve the hydration status and mood of young adults. More research is needed, especially experimental research, to allow causal conclusions to be drawn.

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Fluid intake, hydration status and its association with cognitive function among adolescents in Petaling Perdana, Selangor, Malaysia

Nutrition Research and Practice ◽

10.4162/nrp.2020.14.5.490 ◽

2020 ◽

Vol 14 (5) ◽

pp. 490

Author(s):

Serene En Hui Tung ◽

Yi Zhang Ch'ng ◽

Thaneswary V Karnan ◽

Pei Nee Chong ◽

Jamil Osman Zubaidah ◽

...

Keyword(s):

Cognitive Function ◽

Fluid Intake ◽

Hydration Status

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Fluid Balance, Carbohydrate Ingestion, and Body Temperature During Men’s Stage-Race Cycling in Temperate Environmental Conditions

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2012-0369 ◽

2014 ◽

Vol 9 (3) ◽

pp. 575-582 ◽

Cited By ~ 8

Author(s):

Megan L. Ross ◽

Brian Stephens ◽

Chris R. Abbiss ◽

David T. Martin ◽

Paul B. Laursen ◽

...

Keyword(s):

Environmental Conditions ◽

Fluid Intake ◽

Strong Correlations ◽

Event Duration ◽

Carbohydrate Ingestion ◽

Before And After ◽

Road Cyclists ◽

New Guidelines ◽

The Relationship ◽

Current Guidelines

Purpose:To observe voluntary fluid and carbohydrate intakes and thermoregulatory characteristics of road cyclists during 2 multiday, multiple-stage races in temperate conditions.Methods:Ten internationally competitive male cyclists competed in 2 stage races (2009 Tour of Gippsland, T1, n = 5; 2010 Tour of Geelong, T2, n = 5) in temperate conditions (13.2–15.8°C; 54–80% relative humidity). Body mass (BM) was recorded immediately before and after each stage. Peak gastrointestinal temperature (TGI peak) was recorded throughout each stage. Cyclists recalled the types and volumes of fluid and food consumed throughout each stage.Results:Although fluid intake varied according to the race format, there were strong correlations between fluid intake and distance across all formats of racing, in both tours (r = .82, r = .92). Within a stage, the relationship between finishing time and fluid intake was trivial. Mean BM change over a stage was 1.3%, with losses >2% BM occurring on 5 out of 43 measured occasions and the fastest competitors incurring lower BM changes. Most subjects consumed carbohydrate at rates that met the new guidelines (30–60 g/h for 2–3 h, ~90 g/h for >3 h), based on event duration. There were consistent observations of TGI peak >39°C during stages of T1 (67%) and T2 (73%) despite temperate environmental conditions.Conclusion:This study captured novel effects of highintensity stage racing in temperate environmental conditions. In these conditions, cyclists were generally able to find opportunities to consume fluid and carbohydrate to meet current guidelines. We consistently observed high TGI peak, which merits further investigation.

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Metering of fluid intake and determinants of ad libitum drinking in rats

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1976.231.1.1 ◽

1976 ◽

Vol 231 (1) ◽

pp. 1-8 ◽

Cited By ~ 49

Author(s):

N Rowland ◽

S Nicolaidis

Keyword(s):

Food Intake ◽

Fluid Intake ◽

Base Line ◽

Marked Contrast ◽

Routes Of Administration ◽

Spontaneous Drinking ◽

Ad Libitum ◽

Dry Food ◽

Water Administration ◽

Different Levels

The contributions of homeostatis mechanisms to spontaneous drinking were assessed in a study of residual oral drinking under several conditions of exogenous water administration. Continuous and/or discontinuous infusiors were conducted for long periods with dry food present ad libitum. The routes of administration were intravenous (IV), intragastric (IG) through a nasopharyngeal catheter. All infusions reduced from noninfused levels, but the magnitude of that reduction was a function of both route and temporal characteristics. Continuous infusions were more effective via the IG route than IV, and a residual intake of about 10 ml/24 h presisted at even the highest infusion rates. Discontinuous meal-paired IV infusions suppressed mid- and postmeal drinking, consistent with the satisfaction of systemic needs induced by cry food intake. Meal-paired IG nasopharyngeal infusions competely suppressed drinking when the infusions exceeded base-line intake by only about 20%. In marked contrast, corresponding IG infusions through a direct fistula catheter were relatively ineffective. In all cases the decreases in drinking were not of a nonspecific nature beacuse food intake was unchanged. The discussion considers the different levels of metering involved and the time-varying (derivative) nature of the infusion if was suggested that there is a nonhomeostatic contribution to normal drinking.

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