Blood and urinary measures of hydration status during progressive acute dehydration

L. A. Popowski, R. A. Oppliger, G. Patrick Lambert, R. F. Johnson, A. K. Johnson, C. V. Gisolfi

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Abstract

Purpose: To determine whether: a) plasma osmolarity (Posm) is sensitive to small incremental changes in hydration status, b) urine specific gravity (Usg) can accurately identify a state of euhydration, c) Usg is a sensitive indicator of a change in hydration status, and d) Usg correlates with Posm Methods: Euhydrated (P osm = 288 ± 4 mOsm·L-1) subjects (N = 12) were dehydrated by 5% of their body weight via exercise in the heat (40°C, 20% RH). Posm, urine osmolarity (Uosm), and Usg were measured at 1%, 3%, and 5% dehydration, and 30 and 60 min of recovery (rec). Subjects consumed water in recovery equal to their loss of body weight. Results: Posm increased incrementally with each successive increase in percent body weight loss (%BWL). Usg was not significantly different from baseline until 3% BML. Uosm was not significantly different from baseline until 5% BWL. sg correlated moderately (r = 0.46, P> 0.10) with Posm but reasonably well (r = 0.68, P < 0.02) with Uosm. Conclusions: P osm accurately identifies a state of euhydration and is sensitive to changes in hydration status during acute dehydration and rehydration. Usg and Uosm are also sensitive to changes in hydration status but lag behind during periods of rapid body fluid turnover and therefore correlate only moderately with Posm during acute dehydration.

Original languageEnglish (US)
Pages (from-to)747-753
Number of pages7
JournalMedicine and Science in Sports and Exercise
Volume33
Issue number5
Publication statusPublished - May 3 2001
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Public Health, Environmental and Occupational Health
  • Physical Therapy, Sports Therapy and Rehabilitation
  • Orthopedics and Sports Medicine

Cite this

Popowski, L. A., Oppliger, R. A., Lambert, G. P., Johnson, R. F., Johnson, A. K., & Gisolfi, C. V. (2001). Blood and urinary measures of hydration status during progressive acute dehydration. Medicine and Science in Sports and Exercise, 33(5), 747-753.