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Jason D. Vescovi and Greig Watson

exercise, multiple training sessions sometimes occur on a single day (e.g., training camps), and matches are sometimes played on consecutive days (e.g., field hockey tournaments include ∼5 matches in 7–8 days). The prevalence of minimal hypohydration (first morning urine specific gravity [Usg] = 1.010 − 1

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

could be beneficial. Urine specific gravity (USG) meets both of these requirements and is cost and time effective. However, it is not considered to be an ideal assessment of hydration status unless used in conjunction with additional measurements (e.g., change from average body mass) and if the samples

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Stephanie Van Biervliet, Jean Pierre Van Biervliet, Karel Watteyne, Michel Langlois, Dirk Bernard and Johan Vande Walle

The study aimed to evaluate the effect of exercise on urine sediment in adolescent soccer players. In 25 15-year-old (range 14.4–15.8 yrs) athletes, urinary protein, osmolality and cytology were analyzed by flow cytometry and automated dipstick analysis before (T0), during (T1), and after a match (T2). All athletes had normal urine analysis and blood pressure at rest, tested before the start of the soccer season. Fifty-eight samples were collected (T0: 20, T1: 17, T2: 21). Proteinuria was present in 20 of 38 samples collected after exercise. Proteinuria was associated with increased urinary osmolality (p < .001) and specific gravity (p < .001). Hyaline and granular casts were present in respectively 8 of 38 and 8 of 38 of the urinary samples after exercise. The presence of casts was associated with urine protein concentration, osmolality, and specific gravity. This was also the case for hematuria (25 of 38) and leucocyturia (9 of 38). Squamous epithelial cells were excreted in equal amounts to white and red blood cells. A notable proportion of adolescent athletes developed sediment abnormalities, which were associated with urinary osmolality and specific gravity.

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Robert A. Oppliger, Scott A. Magnes, LeRoy A. Popowski and Carl V. Gisolfi

To reduce the adverse consequences of exertion-related and acute intentional dehydration research has focused on monitoring hydration status. This investigation: 1) compared sensitivity of urine specific gravity (Usg), urine osmolality (Uosm) and a criterion measurement of hydration, plasma osmolality (Posm), at progressive stages of acute hypertonic dehydration and 2) using a medical decision model, determined whether Usg or Uosm accurately reflected hydra-tion status compared to Posm among 51 subjects tested throughout the day. Incremental changes in Posm were observed as subjects dehydrated by 5% of body weight and rehydrated while Usg and Uosm showed delayed dehydration-related changes. Using the medical decision model, sensitivity and specificity were not significant at selected cut-offs for Usg and Uosm. At the most accurate cut-off values, 1.015 and 1.020 for Usg and 700 mosm/kg and 800 mosm/kg for Uosm, only 65% of the athletes were correctly classified using Usg and 63% using Uosm. Posm, Usg, and Uosm appear sensitive to incremental changes in acute hypertonic dehydration, however, the misclassified outcomes for Usg and Uosm raise concerns. Research focused on elucidating the factors affecting accurate assessment of hydration status appears warranted.

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Ioanna Athanasiadou, Sven Christian Voss, Wesal El Saftawy, Hind Al-Jaber, Najib Dbes, Sameera Al-Yazedi, Waseem Samsam, Vidya Mohamed-Ali, Mohammed Alsayrafi, Georgia Valsami and Costas Georgakopoulos

the total content of LH by targeting as many molecular forms as possible. According to the current WADA Technical Document (TD) for the reporting and management of LH findings in male athletes ( WADA TDCG/LH, 2018 ), any value higher than 60 IU/L (after adjustment if specific gravity [SG] is greater

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João C. Dias, Melissa W. Roti, Amy C. Pumerantz, Greig Watson, Daniel A. Judelson, Douglas J. Casa and Lawrence E. Armstrong

Context:

Dieticians, physiologists, athletic trainers, and physicians have recommended refraining from caffeine intake when exercising because of possible fluid-electrolyte imbalances and dehydration.

Objective:

To assess how 16-hour rehydration is affected by caffeine ingestion.

Design:

Dose–response.

Setting:

Environmental chamber.

Participants:

59 college-age men.

Intervention:

Subjects consumed a chronic caffeine dose of 0 (placebo), 3, or 6 mg · kg−1 · day−1 and performed an exercise heat-tolerance test (EHT) consisting of 90 minutes of walking on a treadmill (5.6 km/h) in the heat (37.7 °C).

Outcome Measures:

Fluid-electrolyte measures.

Results:

There were no between-group differences immediately after and 16 hours after EHT in total plasma protein, hematocrit, urine osmolality, specific gravity, color, and volume. Body weights after EHT and the following day (16 hours) were not different between groups (P > .05).

Conclusion:

Hydration status 16 hours after EHT did not change with chronic caffeine ingestion.

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Robert G. Hahn and Nana Waldréus

Purpose:

Urine sampling has previously been evaluated for detecting dehydration in young male athletes. The present study investigated whether urine analysis can serve as a measure of dehydration in men and women of a wide age span.

Methods:

Urine sampling and body weight measurement were undertaken before and after recreational physical exercise (median time: 90 min) in 57 volunteers age 17–69 years (mean age: 42). Urine analysis included urine color, osmolality, specific gravity, and creatinine.

Results:

The volunteers’ body weight decreased 1.1% (mean) while they exercised. There were strong correlations between all 4 urinary markers of dehydration (r = .73–.84, p < .001). Researchers constructed a composite dehydration index graded from 1 to 6 based on these markers. This index changed from 2.70 before exercising to 3.55 after exercising, which corresponded to dehydration of 1.0% as given by a preliminary reference curve based on 7 previous studies in athletes. Men were slightly dehydrated at baseline (mean: 1.9%) compared with women (mean: 0.7%; p < .001), though age had no influence on the results. A final reference curve that considered both the present results and the 7 previous studies was constructed in which exercise-induced weight loss (x) was predicted by the exponential equation x = 0.20 dehydration index1.86.

Conclusion:

Urine sampling can be used to estimate weight loss due to dehydration in adults up to age 70. A robust dehydration index based on four indicators reduces the influence of confounders.

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Daniel Jolley, Brian Dawson, Shane K. Maloney, James White, Carmel Goodman and Peter Peeling

This study investigated the influence of dehydration on urinary levels of pseudoephedrine (PSE) after prolonged repeated effort activity. Fourteen athletes performed a simulated team game circuit (STGC) outdoors over 120 min under three different hydration protocols: hydrated (HYD), dehydrated (DHY) and dehydrated + postexercise fluid bolus (BOL). In all trials, a 60 mg dose of PSE was administered 30 min before trial and at half time of the STGC. Urinary PSE levels were measured before drug administration and at 90 min postexercise. In addition, body mass (BM) changes and urinary specific gravity (USG), osmolality (OSM), creatinine (Cr), and pH values were recorded. No differences in PSE levels were found 90 min postexercise between conditions (HYD: 208.5 ± 116.5; DHY: 238.9 ± 93.5; BOL: 195.6 ± 107.3 μg·ml−1), although large variations were seen within and between participants across conditions (range: 33–475 μg·ml−1: ICC r = .03–0.16, p > .05). There were no differences between conditions in USG, OSM, pH or PSE/Cr ratio. In conclusion, hydration status did not influence urinary PSE levels after prolonged repeated effort activity, with ~70% of samples greater than the WADA limit (>150 μg.ml−1), and ~30% under. Due to the unpredictability of urinary PSE values, athletes should avoid taking any medications containing PSE during competition.

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Lawrence E. Armstrong, Amy C. Pumerantz, Kelly A. Fiala, Melissa W. Roti, Stavros A. Kavouras, Douglas J. Casa and Carl M. Maresh

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.

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Lawrence E. Armstrong, Jorge A. Herrera Soto, Frank T. Hacker Jr., Douglas J. Casa, Stavros A. Kavouras and Carl M. Maresh

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.