Table 3

Dehydration defined by urine osmolality (UOsm) whereas dehydration is any UOsm ≥700 mOsmol/kg/H2O, while adequately hydrated is any UOsm <700 mOsmol/kg/H2O

VariableDehydrated
mean±SD n=174
Hydrated
mean±SD n=144
Serum [Na+]
(mmol/L)
140.3±2.0139.4±2.1***
Serum [K+]
(mmol/L)
4.4±0.34.4±0.4
Serum osmolality
(mOsmol/kgH2O)
280.7±9.1280.4±8.0
Urine osmolality
(mOsmol/kgH2O)
918.7±127.9397.4±181.0***
Urine specific gravity1.017±0.0051.011±0.005***
Thirst rating (0–10)4.6±1.74.0±2.0**
  • By this definition, 55% of the athletes were dehydrated.

  • *P<0.05; **P<0.01; ***P<0.001 between dehydrated versus hydrated.

  • serum [K+], potassium concentration; serum [Na+], sodium concentration.