scholarly journals The psychophysiological effects of a three day dry fast: A self-experimentation case study

2020 ◽  
Author(s):  
Harriet Carroll
Keyword(s):  
Blood Pressure ◽  
Blood Glucose ◽  
Specific Gravity ◽  
Sleep Quality ◽  
Body Mass ◽  
Urine Volume ◽  
Urine Specific Gravity ◽  
Hydration Status ◽  
Fluid Restriction ◽  
Urine Colour

Background: A commonly held belief is that humans cannot survive more than a few days without fluid intake. The source of this is unclear, but does not accord with the few controlled studies that have been conducted to investigate the effects of fluid abstention, nor the few extreme cases of fluid restriction. Methods: This was a self-experimentation, with one day pre-load of fluid and salt (DAY 0), three days complete fluid abstention (< 45 g/d water from food only) (DAYS 1-3), and 24 h rehydration (DAY 4). Days ran from 1500 h to 1500 h. The following measures were taken across various time points across each day: body mass; urine volume; urine colour; urine specific gravity; finger-prick blood glucose concentration; blood pressure; pulse; body temperature; dietary intake; and visual analogue scales (VAS) of food-appetites (satiety and desires), thirst-appetites, mood, wakefulness, and sleep quality. Results: By the end of DAY 3, body water (excluding estimated lean/adipose loss from negative energy balance) decreased by ~1.8 % from 1500 h on DAY 0, or ~4.0 % from 1500 h on DAY 1 (after a fluid preload). With this reduction in body mass came expected reductions in urine volume and increased in urine colour, though trends in urine specific gravity were less pronounced. Blood pressure trended towards being lower during DAYS 1-3 and increased during DAY 4. Whole blood glucose concentrations also tended towards being lower during DAYS 1-3 compared to DAY 4, particularly postprandially. Hunger tended to be reduced during DAYS 1-3, but increased again during DAY 4. Wanting to eat appeared to be a separate construct to hunger/fullness. True-thirst was higher during DAYS 1-3 relative to DAY 4, and this synchronised well with true-xerostomia and ratings of dryness of lips. However, sensational-xerostomia was the dominant thirst experienced during DAY 1-3. Sadness was moderately inversely correlated with body mass loss (r = 0.57) and tiredness was strongly positively correlated (r = 0.94). Sleep quality was unrelated to hydration status. Conclusion: Overall, the expected changes occurred in terms of hydration physiology, but with some unexpected findings in terms of gluco-regulation, blood pressure, and thirst appetites.

Human Hydration Indices: Acute and Longitudinal Reference Values

2010 ◽  
Vol 20 (2) ◽  
pp. 145-153 ◽  
Author(s):  
Lawrence E. Armstrong ◽  
Amy C. Pumerantz ◽  
Kelly A. Fiala ◽  
Melissa W. Roti ◽  
Stavros A. Kavouras ◽  
...  
Keyword(s):  
Specific Gravity ◽  
Body Mass ◽  
Reference Values ◽  
Fluid Intake ◽  
Pure Water ◽  
Urine Volume ◽  
Urine Specific Gravity ◽  
Hydration Status ◽  
Total Fluid Intake ◽  
Free Living

It is difficult to describe hydration status and hydration extremes because fluid intakes and excretion patterns of free-living individuals are poorly documented and regulation of human water balance is complex and dynamic. This investigation provided reference values for euhydration (i.e., body mass, daily fluid intake, serum osmolality; M ± SD); it also compared urinary indices in initial morning samples and 24-hr collections. Five observations of 59 healthy, active men (age 22 ± 3 yr, body mass 75.1 ± 7.9 kg) occurred during a 12-d period. Participants maintained detailed records of daily food and fluid intake and exercise. Results indicated that the mean total fluid intake in beverages, pure water, and solid foods was >2.1 L/24 hr (range 1.382–3.261, 95% confidence interval 0.970–3.778 L/24 hr); mean urine volume was >1.3 L/24 hr (0.875–2.250 and 0.675–3.000 L/24 hr); mean urine specific gravity was >1.018 (1.011–1.027 and 1.009–1.030); and mean urine color was ≥4 (4–6 and 2–7). However, these men rarely (0–2% of measurements) achieved a urine specific gravity below 1.010 or color of 1. The first morning urine sample was more concentrated than the 24-h urine collection, likely because fluids were not consumed overnight. Furthermore, urine specific gravity and osmolality were strongly correlated (r2 = .81–.91, p < .001) in both morning and 24-hr collections. These findings provide euhydration reference values and hydration extremes for 7 commonly used indices in free-living, healthy, active men who were not exercising in a hot environment or training strenuously.

scholarly journals Effects of sex and menstrual cycle on volume-regulatory responses to 24-h fluid restriction

2020 ◽  
Vol 319 (5) ◽  
pp. R560-R565
Author(s):  
Gabrielle E. W. Giersch ◽  
Abigail T. Colburn ◽  
Margaret C. Morrissey ◽  
Cody R. Butler ◽  
Michaela L. Pruchnicki ◽  
...  
Keyword(s):  
Menstrual Cycle ◽  
Specific Gravity ◽  
Body Mass ◽  
Urine Osmolality ◽  
Reproductive Hormones ◽  
Urine Specific Gravity ◽  
Fluid Restriction ◽  
Urine Color ◽  
Fluid Regulation ◽  
The Impact

Reproductive hormones have significant nonreproductive physiological effects, including altering fluid regulation. Our purpose was to explore the impact of sex and menstrual cycle (MC) phase on volume-regulatory responses to 24-h fluid restriction (24-h FR). Participants (men: n = 12, 20 ± 2 yr; women: n = 10, 20 ± 1 yr) were assigned two randomized and counterbalanced fluid prescriptions [Euhy: euhydrated, urine specific gravity (USG) < 1.020; Dehy: 24-h FR, USG > 1.020]. Men completed both (MEuhy, MDehy), while women completed both in the late-follicular ( days 10–13; FDehy, FEuhy) and midluteal ( days 18–22; LDehy, LEuhy) phases. We measured body mass, plasma and urine osmolality (Posm, Uosm), urine specific gravity (USG), urine color (Ucol), and serum copeptin; 24-h FR yielded mild dehydration without influence of sex or MC ( P > 0.05). Copeptin increased in men following Dehy (pre: 8.2 ± 5.2, post: 15.8 ± 12.6, P = 0.04) but not in women (FDehy pre: 4.3 ± 1.6, post: 10.5 ± 6.9, P = 0.06; LDehy pre: 5.6 ± 3.5, post: 10.4 ± 6.2, P = 0.16). In FDehy, Posm increased following FR (pre: 288 ± 2, post: 292 ± 1, P = 0.03) but not in men (pre: 292 ± 3, post: 293 ± 2, P = 0.46). No MC differences were observed between body mass loss, Posm, Uosm, USG, and copeptin ( P > 0.05). These results suggest that volume-regulatory responses to 24-h FR were present in men but not in women, without apparent effects of the menstrual cycle.

Hydration status of Greco-Roman wrestlers in an authentic precompetition situation

2013 ◽  
Vol 38 (6) ◽  
pp. 621-625 ◽  
Author(s):  
Vahur Ööpik ◽  
Saima Timpmann ◽  
Andres Burk ◽  
Innar Hannus
Keyword(s):  
Specific Gravity ◽  
Body Mass ◽  
Urine Osmolality ◽  
Mass Gain ◽  
The Body ◽  
Urine Specific Gravity ◽  
Hydration Status ◽  
Greco Roman ◽  
Reduced Body ◽  
Body Mass Gain

We assessed the urinary indexes of hydration status of Greco-Roman wrestlers in an authentic precompetition situation at the time of official weigh-in (OWI). A total of 51 of 89 wrestlers competing in the Estonian Championship in 2009 donated a urine sample. Questionnaire responses revealed that 27 wrestlers (body mass losers (BMLs)) reduced body mass before the competition, whereas 24 wrestlers (those who do not lose body mass (n-BMLs)) did not. In 42 wrestlers, values of urine specific gravity ≥1.020 and urine osmolality ≥700 mOsmol·kg−1 revealed a hypohydrated status. The prevalence of hypohydration in the BMLs (96%) was higher than in the n-BMLs (67%) (χ2 = 7.68; p < 0.05). The prevalence of serious hypohydration (urine specific gravity >1.030) was 5.3 times greater (χ2 = 8.32; p < 0.05) in the BMLs than in the n-BMLs. In the BMLs, the extent of body mass gain during the 16-h recovery (2.5 ± 1.2 kg) was associated (r = 0.764; p < 0.05) with self-reported precompetition body mass loss (4.3 ± 2.0 kg) and exceeded the body mass gain observed in the n-BMLs (0.7 ± 1.2 kg; p < 0.05). We conclude that hypohydration is prevalent among Greco-Roman wrestlers at the time of OWI. The prevalence of hypohydration and serious hypohydration is especially high among wrestlers who are accustomed to reducing body mass before competition. These results suggest that an effective rehydration strategy is needed for Olympic-style wrestlers, and that changes in wrestling rules should be considered to reduce the prevalence of harmful body mass management behaviours.

Hydration Status and Sodium Balance of Endurance Runners Consuming Postexercise Supplements of Varying Nutrient Content

2015 ◽  
Vol 25 (5) ◽  
pp. 471-479 ◽  
Author(s):  
J. Luke Pryor ◽  
Evan C. Johnson ◽  
Jeffery Del Favero ◽  
Andrew Monteleone ◽  
Lawrence E. Armstrong ◽  
...  
Keyword(s):  
Body Mass ◽  
Sodium Intake ◽  
Urine Volume ◽  
Nutrient Content ◽  
Urinary Sodium Excretion ◽  
Nutritional Supplement ◽  
Running Economy ◽  
Urine Specific Gravity ◽  
Sodium Balance ◽  
Hydration Status

Postexercise protein and sodium supplementation may aid recovery and rehydration. Preserved beef provides protein and contains high quantities of sodium that may alter performance related variables in runners. The purpose of this study was to determine the effects of consuming a commercial beef product postexercise on sodium and water balance. A secondary objective was to characterize effects of the supplementation protocols on hydration, blood pressure, body mass, and running economy. Eight trained males (age = 22 ± 3 y, V̇O2max = 66.4 ± 4.2 ml·kg-1·min-1) completed three identical weeks of run training (6 run·wk-1, 45 ± 6 min·run-1, 74 ± 5% HRR). After exercise, subjects consumed either, a beef nutritional supplement (beef jerky; [B]), a standard recovery drink (SRD), or SRD+B in a randomized counterbalanced design. Hydration status was assessed via urinary biomarkers and body mass. No main effects of treatment were observed for 24 hr urine volume (SRD, 1.7 ± 0.5; B, 1.8 ± 0.6; SRD+B, 1.4 ± 0.4 L·d-1), urine specific gravity (1.016 ± 0.005, 1.018 ± 0.006, 1.017 ± 0.006) or body mass (68.4 ± 8.2, 68.3 ± 7.7, 68.2 ± 8.1 kg). No main effect of treatment existed for sodium intake—loss (-713 ± 1486; -973 ± 1123; -980 ± 1220 mg·d-1). Mean arterial pressure (81.0 ± 4.6, 81.1 ± 7.3, 83.8 ± 5.4 mm Hg) and average exercise running economy (V̇O2: SRD, 47.9 ± 3.2; B, 47.2 ± 2.6; SRD+B, 46.2 ± 3.4 ml·kg-1·min-1) was not affected. Urinary sodium excretion accounted for the daily sodium intake due to the beef nutritional supplement. Findings suggest the commercial beef snack is a viable recovery supplement following endurance exercise without concern for hydration status, performance decrements, or cardiovascular consequences.

scholarly journals Influence of progressive fluid restriction on mood and physiological markers of dehydration in women

2012 ◽  
Vol 109 (2) ◽  
pp. 313-321 ◽  
Author(s):  
Nathalie Pross ◽  
Agnès Demazières ◽  
Nicolas Girard ◽  
Romain Barnouin ◽  
Francine Santoro ◽  
...  
Keyword(s):  
Specific Gravity ◽  
Water Intake ◽  
Vital Signs ◽  
Plasma Osmolality ◽  
Physiological Parameters ◽  
Urine Specific Gravity ◽  
Hydration Status ◽  
Fluid Restriction ◽  
Experimental Conditions ◽  
Physiological Markers

The present study evaluated, using a well-controlled dehydration protocol, the effects of 24 h fluid deprivation (FD) on selected mood and physiological parameters. In the present cross-over study, twenty healthy women (age 25 (se 0·78) years) participated in two randomised sessions: FD-induced dehydration v. a fully hydrated control condition. In the FD period, the last water intake was between 18.00 and 19.00 hours and no beverages were allowed until 18.00 hours on the next day (23–24 h). Water intake was only permitted at fixed periods during the control condition. Physiological parameters in the urine, blood and saliva (osmolality) as well as mood and sensations (headache and thirst) were compared across the experimental conditions. Safety was monitored throughout the study. The FD protocol was effective as indicated by a significant reduction in urine output. No clinical abnormalities of biological parameters or vital signs were observed, although heart rate was increased by FD. Increased urine specific gravity, darker urine colour and increased thirst were early markers of dehydration. Interestingly, dehydration also induced a significant increase in saliva osmolality at the end of the 24 h FD period but plasma osmolality remained unchanged. The significant effects of FD on mood included decreased alertness and increased sleepiness, fatigue and confusion. The most consistent effects of mild dehydration on mood are on sleep/wake parameters. Urine specific gravity appears to be the best physiological measure of hydration status in subjects with a normal level of activity; saliva osmolality is another reliable and non-invasive method for assessing hydration status.

scholarly journals OR-055 Effect of whey protein on rehydration after exercise

2018 ◽  
Vol 1 (2) ◽  
Author(s):  
Lantian Zhang ◽  
Chenge Dang ◽  
Chunyan Xu
Keyword(s):  
Specific Gravity ◽  
Whey Protein ◽  
Body Mass ◽  
Intermittent Exercise ◽  
Urine Volume ◽  
Urine Osmolality ◽  
The Body ◽  
Urine Specific Gravity ◽  
Moderate Intensity ◽  
Exercise Induced

Objective The purpose of this study is to determine the effects of a rehydration solution containing whey protein on fluid balance after exercise-induced dehydration.The ACSM Sports Guide recommends that healthy adults exercise moderate-intensity aerobic exercise for 30 minutes a day.This type of exercise can dehydrate the body by about 1%.Dehydration 1% affects exercise capacity and performance.The purpose of this study was to exercise-induced dehydration of sports drinks containing whey protein. Methods Twelve college students ( 20 ± 2 years, 169.9 ± 8.1 cm, 63.3 ± 13 kg) participated. Participants reduced body mass by (0.67±0.33) after intermittent exercise and re-hydrated with a volume of drink in liter equivalent to 1.5 times their body mass loss in kilograms of a solution of 4 kinds of drinks：Distilled water(trial C), carbohydrate-electrolyte(trail D), carbohydrate-electrolyte-low whey protein(trial LWP) and carbohydrate-electrolyte-high whey protein(trail HWP). Solutions were matched for carbohydrate and electrolyte content in trail D、LWP and HWP. Trials were administered in a random, counterbalanced, crossover design, with subjects blinded as to which drink they consumed during each trial.  Each participant completed 4 experimental trials, which were separated by at least one week. Urine samples were collected before and after exercise (immediately, 40、80、120、160minutes later). Urine volume, drink retention, urine osmolality and urine specific gravity were tested. Drink retention was calculated as difference between the volume of drink ingested and urine produced. Results 1.Total cumulative urine output after exercise was not different between each of the four groups(C:1002 ±102mL;D:;LWP: ;HWP:，p>0.5 )； 2. During the study, drink retention of trail LWP is the highest(80.3±11.2%), but there was not different between each of the four groups(C: 70.5±20.6%;D:70.7±17.9% ;HWP: 75.0±12.4%， p>0.5). 3. At the 40th minute after exercise, the urine specific gravity of the D was significantly lower than that of the LWP(1.020±0.006 vs 1.028±0.003, p=0.020), and the urine specific gravity of the LWP at 120 minutes after exercise significantly higher than the D (1.018 ± 0.003 vs 1.021 ± 0.007, p = 0.006). Conclusions When the amount of dehydration after exercise is 1%-2%, each kind of the drinks in the study is useful for rehydration， and the addition of whey protein does not increase rehydration.

Carbohydrate exerts a mild influence on fluid retention following exercise-induced dehydration

2010 ◽  
Vol 108 (2) ◽  
pp. 245-250 ◽  
Author(s):  
Kristin L. Osterberg ◽  
Shannon E. Pallardy ◽  
Richard J. Johnson ◽  
Craig A. Horswill
Keyword(s):  
Body Mass ◽  
Urine Volume ◽  
Fluid Retention ◽  
Urine Specific Gravity ◽  
Hydration Status ◽  
Excessive Sweating ◽  
Rehydration Solutions ◽  
Before And After ◽  
Postexercise Recovery ◽  
Exercise Induced

Rapid and complete rehydration, or restoration of fluid spaces, is important when acute illness or excessive sweating has compromised hydration status. Many studies have investigated the effects of graded concentrations of sodium and other electrolytes in rehydration solutions; however, no study to date has determined the effect of carbohydrate on fluid retention when electrolyte concentrations are held constant. The purpose of this study was to determine the effect of graded levels of carbohydrate on fluid retention following exercise-induced dehydration. Fifteen heat-acclimatized men exercised in the heat for 90 min with no fluid to induce 2–3% dehydration. After a 30-min equilibration period, they received, over the course of 60 min, one of five test beverages equal to 100% of the acute change in body mass. The experimental beverages consisted of a flavored placebo with no electrolytes (P), placebo with electrolytes (P + E), 3%, 6%, and 12% carbohydrate solutions with electrolytes. All beverages contained the same type and concentration of electrolytes (18 meq/l Na+, 3 meq/l K+, 11 meq/l Cl−). Subjects voided their bladders at 60, 90, 120, 180, and 240 min, and urine specific gravity and urine volume were measured. Blood samples were taken before exercise and 30, 90, 180, and 240 min following exercise and were analyzed for glucose, sodium, hemoglobin, hematocrit, renin, aldosterone, and osmolality. Body mass was measured before and after exercise and a final body mass was taken at 240 min. There were no differences in percent dehydration, sweat loss, or fluid intake between trials. Fluid retention was significantly greater for all carbohydrate beverages compared with P (66.3 ± 14.4%). P + E (71.8 ± 9.9%) was not different from water, 3% (75.4 ± 7.8%) or 6% (75.4 ± 16.4%) but was significantly less than 12% (82.4 ± 9.2%) retention of the ingested fluid. No difference was found between the carbohydrate beverages. Carbohydrate at the levels measured exerts a mild influence on fluid retention in postexercise recovery.

Relationships Between WUT (Body Weight, Urine Color, and Thirst Level) Criteria and Urine Indices of Hydration Status

2021 ◽  
pp. 194173812110384
Author(s):  
Yasuki Sekiguchi ◽  
Courteney L. Benjamin ◽  
Cody R. Butler ◽  
Margaret C. Morrissey ◽  
Erica M. Filep ◽  
...  
Keyword(s):  
Specific Gravity ◽  
Mass Loss ◽  
Body Mass ◽  
Urine Osmolality ◽  
Urine Specific Gravity ◽  
Venn Diagram ◽  
Hydration Status ◽  
Body Mass Loss ◽  
Living Situation ◽  
Urine Color

Background: A Venn diagram consisting of percentage body mass loss, urine color, and thirst perception (weight, urine, thirst [WUT]) has been suggested as a practical method to assess hydration status. However, no study to date has examined relationships between WUT and urine hydration indices. Thus, the purpose of this study was to investigate relationships between urine specific gravity, urine osmolality, and the WUT criteria. Hypothesis: Urine specific gravity and urine osmolality indicate hypohydration when the WUT criteria demonstrate hypohydration (≥2 markers). Study Design: Laboratory cohort study. Level of Evidence: Level 3. Methods: A total of 22 women (mean ± SD; age, 20 ± 1 years; mass, 65.4 ± 12.6 kg) and 21 men (age, 21 ± 1 years; body mass, 78.7 ± 14.6 kg) participated in this study. First morning body mass, urine color, urine specific gravity, urine osmolality, and thirst level were collected for 10 consecutive days in a free-living situation. Body mass loss >1%, urine color >5, and thirst level ≥5 were used as the dehydration thresholds. The number of markers that indicated dehydration levels were counted and categorized into either 3, 2, 1, or 0 WUT markers that indicated dehydration. One-way analysis of variance with Tukey pairwise comparisons was used to assess the differences in urine specific gravity and urine osmolality between the different number of WUT markers. Results: Urine specific gravity in 3 WUT markers (mean ± SD [effect size], 1.021 ± 0.007 [0.57]; P = 0.025) and 2 WUT markers (1.019 ± 0.010 [0.31]; P = 0.026) was significantly higher than 1 WUT marker (1.016 ± 0.009). Urine mosmolality in 2 WUT markers (705 ± 253 mOsmol [0.43]; P = 0.018) was significantly higher than 1 WUT (597 ± 253 mOsmol). Meeting at least 2 WUT markers resulted in sensitivities of 0.652 (2 WUT criteria met) and 0.933 (3 WUT criteria met) to detect urine osmolality >700 mOsmol. Conclusion: These results suggest that when 3 WUT markers are met, urine specific gravity and urine osmolality were greater than euhydration cutoff points. The WUT criterion is a useful tool to use in field settings to assess hydration status when first morning urine sample was used. Clinical Relevance: Athletes, coaches, sports scientists, and medical professionals can use WUT criteria to monitor dehydration with reduced cost and time.

Urine Specific Gravity as a Practical Marker for Identifying Suboptimal Fluid Intake of Runners ∼12-hr Postexercise

2019 ◽  
Vol 29 (1) ◽  
pp. 32-38
Author(s):  
Eric Kyle O’Neal ◽  
Samantha Louise Johnson ◽  
Brett Alan Davis ◽  
Veronika Pribyslavska ◽  
Mary Caitlin Stevenson-Wilcoxson
Keyword(s):  
Specific Gravity ◽  
Body Mass ◽  
Fluid Intake ◽  
Area Under The Curve ◽  
Fluid Replacement ◽  
Urine Specific Gravity ◽  
Hydration Status ◽  
Accuracy Score ◽  
Characteristic Area ◽  
Almost All

The legitimacy of urine specific gravity (USG) as a stand-alone measure to detect hydration status has recently been challenged. As an alternative to hydration status, the purpose of this study was to determine the diagnostic capability of using the traditional USG marker of >1.020 to detect insufficient recovery fluid consumption with consideration for moderate versus high sweat losses (2.00–2.99 or >3% body mass, respectively). Adequate recovery fluid intake was operationally defined as ≥100% beverage fluid intake plus food water from one or two meals and a snack. Runners (n = 59) provided 132 samples from five previous investigations in which USG was assessed 10–14 hr after 60–90 min runs in temperate-to-hot environments. Samples were collected after a meal (n = 58) and after waking (n = 74). When sweat losses exceeded 3% body mass (n = 60), the relationship between fluid replacement percentage and USG increased from r = −.55 to −.70. Correct diagnostic decision improved from 66.6 to 83.3%, and receiver operating characteristic area under the curve increased the diagnostic accuracy score from 0.76 to approaching excellent (0.86). Artifacts of significant prerun hyperhydration (eight of 15 samples has USG <1.005) may explain false positive diagnoses, while almost all (84%) cases of false positives were found when sweat losses were <3.0% of body mass. Evidence from this study suggests that euhydrated runners experiencing significant sweat losses who fail to reach adequate recovery fluid intake levels can be identified by USG irrespective of acute meal and fluid intake ∼12-hr postrun.

Urinary Indices during Dehydration, Exercise, and Rehydration

1998 ◽  
Vol 8 (4) ◽  
pp. 345-355 ◽  
Author(s):  
Lawrence E. Armstrong ◽  
Jorge A. Herrera Soto ◽  
Frank T. Hacker ◽  
Douglas J. Casa ◽  
Stavros A. Kavouras ◽  
...  
Keyword(s):  
Specific Gravity ◽  
Body Mass ◽  
Urine Volume ◽  
Plasma Osmolality ◽  
Body Water ◽  
Hydration Status ◽  
Plasma Sodium ◽  
Oral Rehydration ◽  
Urine Color ◽  
Better Than

This investigation evaluated the validity and sensitivity of urine color (Ucol), specific gravity (Usg), and osmolality (Uosm) as indices of hydration status, by comparing them to changes in body water. Nine highly trained males underwent a 42-hr protocol involving dehydration to 3.7% of body mass (Day 1, −2.64 kg), cycling to exhaustion (Day 2, −5.2% of body mass, −3.68 kg), and oral rehydration for 21 hr. The ranges of mean (across time) blood and urine values were Ucol, 1-7; Usg, 1.004-1.029; U08m, 117-1,081 mOsm • kg−1; and plasma osmolality (Posm), 280-298 mOsm ⋅ kg−1. Urine color tracked changes in body water as effectively as (or better than) Uosm, Usg, urine volume, Posm, plasma sodium, and plasma total protein. We concluded that (a) Ucol, Uosm, and Usg are valid indices of hydration status, and (b) marked dehydration, exercise, and rehydration had little effect on the validity and sensitivity of these indices.

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