title: Urine output and performance of runners in a 12-hour ultramarathon.
abstract: OBJECTIVE
  To understand the urination pattern and to determine the relationships between urine output and performance of ultramarathon runners.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  The 2005 Soochow University international ultramarathon, in which each athlete ran for 12 hours.
  
  
  METHODS
  All entrants in the 12-hour race were invited to participate in the study.
  
  
  METHODS
  None.
  
  
  METHODS
  Athletes were weighed immediately before and after the race. Urine samples were collected during the race and immediately after the race.
  
  
  RESULTS
  There was a trend toward better performance of the group with less urination (LU), although the difference was not statistically significant. Further analysis of hourly running distances between groups showed better performance in the group with LU during the first 11 hours of the competition. Comparison of athletes in 3 levels of running distance (tertiles) showed statistically significant differences between groups in total urine output. The fastest tertile had lower prerace body weight and greater body weight change than the slowest and intermediate tertiles, but the differences were not statistically significant. Linear regression analysis using the stepwise method showed that total urine output and prerace body weight were negatively associated with performance.
  
  
  CONCLUSIONS
  Runners with LU had better performance during the first 11 hours of the competition. Linear regression analysis showed that total urine output and prerace body weight were negatively associated with performance.
authors.affiliation: Institute of Emergency and Critical Care Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors.forename: Teh-Fu
authors.initials: TF
authors.lastname: Hsu
authors.forename: Ying-Ju
authors.initials: YJ
authors.lastname: Chen
authors.forename: Shang-Lin
authors.initials: SL
authors.lastname: Chou
authors.forename: Wei-Fong
authors.initials: WF
authors.lastname: Kao
authors.forename: Ju-Sing
authors.initials: JS
authors.lastname: Fan
authors.forename: Jin-Jong
authors.initials: JJ
authors.lastname: Chen
authors.forename: Fon-Chu
authors.initials: FC
authors.lastname: Kuo
authors.forename: David H T
authors.initials: DH
authors.lastname: Yen
authors.forename: Chun-I
authors.initials: CI
authors.lastname: Huang
mesh_terms: D000328:Adult; D000368:Aged; D054874:Athletic Performance / Q000502:physiology*; D001835:Body Weight; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012420:Running / Q000502:physiology*; D013997:Time Factors; D014554:Urination