Urinary Indices during Dehydration, Exercise, and Rehydration

Abstract

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.

Isotonic saline in elderly men: an open‐labelled controlled infusion study of electrolyte balance, urine flow and kidney function

“…Analysis of urine concentrations for various metabolic waste products, which appear in higher concentrations when the kidneys conserve water, has been used to diagnose dehydration in sports medicine [12,13]. The urinary creatinine concentration and the urinary osmolality show a 10-fold variation in healthy humans [14], and this can be attributed to how the kidneys are set to excrete or conserve water.…”

“…Creatinine and osmotically active particles are excreted at a fairly constant rate. Therefore, reduced excretion of water can be indicated by a raised urinary creatinine concentration and urinary osmolality [12][13][14]. Pre-infusion fluid retention was diagnosed when the creatinine concentration in the urine collected before the infusions started was > 7.0 mmol.l À1 and/or the osmolality was > 700 mOsmol.kg À1 .…”

Nível de desidratação após treinamento de ciclismo indoor

“…Além disso, a densidade da urina tem sido considerada como um interessante método não invasivo para a avaliação do estado de hidratação dos atletas 15 . Segundo National Athletic Trainers' Association 16 , os valores para determinar o estado de hidratação segundo a densidade da urina são: hipohidratação = ≥1030; Euhidratados = 1013 a 1029; Hiperhidratação = 1001 a 1012.…”

Effect of increased plasma osmolality on cold-induced thirst attenuation

“…All volunteers were euhydrated prior to the start of the day 1 dehydration protocol as determined by urine speciWc gravity <1.02 and P osm < 290 mOsm kg ¡1 (Armstrong et al 1998) (Table 1). Changes in body mass, urine speciWc gravity, and P osm resulting from the day 1 dehydration protocol are presented in Table 1.…”

“…Subjects reported to the laboratory on the afternoon of day 1. A urine speciWc gravity (USG; Spartan Refractometer, model A 300 CL, Japan) of less than 1.020 (Armstrong et al 1998) was used to verify that subjects were adequately hydrated prior to dehydration. A Polar monitor (Polar Accurex II, Polar Instruments) was attached to each subjects chest for heart rate (HR) and a Xexible rectal probe (Yellow Springs Instruments, series 401, Yellow Springs, OH, USA) was inserted »10 cm past the anal sphincter to monitor core temperature (T re ).…”