title: Evaluation of hydration status by urine, body mass variation and plasma parameters during an official half-marathon.
abstract: BACKGROUND
  The aim of this study was to verify the agreement of urine, body mass variations and plasma parameters to determine the hydration status of 14 male runners (29±4 years and 54.3±5.5 mLO2/kg/min) in an official 21.1 km road race.
  
  
  METHODS
  The mean dry-bulb temperature and air relative humidity during the road race were 25.1±2.1 °C and 54.7±2.2%, respectively. The volume of water ingested by the runners was monitored using marked volumetric plastic bottles provided at the hydration stations located at 0, 2.5, 5.0, 7.5, 10.5, 14.0, 16.0 and 18.5 km from the starting line. Hydration status was assessed using urine specific gravity (USG), urine osmolality (UOSM) and plasma osmolality (POSM). Furthermore, body mass variation (∆BM) was assessed by comparing body mass (BM) immediately prior and after the race. Total sweat was estimated by ∆BM, added water volume ingested and deducted blood volume collected. The sweat rate was calculated through total sweat and total exercise time.
  
  
  RESULTS
  The mean water intake was 0.82±0.40 L, and the mean sweat rate and total sweating were 1440.11±182.13 mL/h and 2.67±0.23 L. After the race, the BM reduced by 1.7±0.4 kg. The ∆BM was -2.41±0.47%, and the plasma volume variation was -9.79±4.6% between pre- and post-running measurements. Despite the POSM increased post-race compared to pre-race, the UOSM and USG did not change. No significant correlations were found between POSM variation with UOSM variation (r=-0.08; P=0.71), USG variation (r=-0.11; P=0.78) or ∆BM (r=0.09; P=0.77).
  
  
  CONCLUSIONS
  In conclusion, this study shows that both ∆BM and ∆POSM indicated a hypohydration state after exercise even though the ∆BM did not correlate significantly with ∆POSM. These results demonstrate that ∆BM is a practical method and can be sufficiently sensitive to evaluate the hydration state, but it should be utilized with caution.
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil.|University Center of Sete Lagoas, Sete Lagoas, Brazil.
authors.forename: Emerson R
authors.initials: ER
authors.lastname: Pereira
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Marcelo T
authors.initials: MT
authors.lastname: de Andrade
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil.|Department of Physical Education, Federal University of Maranhão, São Luís, Brazil.
authors.forename: Thiago T
authors.initials: TT
authors.lastname: Mendes
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil.|Exercise Physiology, Brazilian Football Confederation, Teresópolis, Brazil.
authors.forename: Guilherme P
authors.initials: GP
authors.lastname: Ramos
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: André
authors.initials: A
authors.lastname: Maia-Lima
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Eliney S
authors.initials: ES
authors.lastname: Melo
authors.affiliation: State University of Minas Gerais, Ibirité, Brazil.
authors.forename: Moisés V
authors.initials: MV
authors.lastname: Carvalho
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Carolina F
authors.initials: CF
authors.lastname: Wilke
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Luciano S
authors.initials: LS
authors.lastname: Prado
authors.affiliation: Federal University of Minas Gerais, Belo Horizonte, Brazil - emerson_silami@yahoo.com.br.|Department of Physical Education, Federal University of Maranhão, São Luís, Brazil.
authors.forename: Emerson
authors.initials: E
authors.lastname: Silami-Garcia
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D015992:Body Mass Index; D003681:Dehydration / Q000097:blood / Q000652:urine*; D004326:Drinking / Q000502:physiology; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D010953:Plasma Volume / Q000502:physiology; D012420:Running / Q000502:physiology*; D013546:Sweating / Q000502:physiology; D016482:Urinalysis
chemical_list: D015415:Biomarkers