title: Athletic performance and serial weight changes during 12- and 24-hour ultra-marathons.
abstract: OBJECTIVE
  The principal objective of this study was to evaluate serial weight changes in athletes during 12- and 24-hour ultra-marathons and to correlate these changes with athletic performance, namely the distance covered.
  
  
  METHODS
  This was a prospective study.
  
  
  METHODS
  The 2003 Soochow University international ultra-marathon.
  
  
  METHODS
  Fifty-two race participants.
  
  
  METHODS
  12- or 24-hour ultra-marathon.
  
  
  METHODS
  Body weight changes were measured before, at 4-hour intervals during, and immediately after the 12- and 24-hour races.
  
  
  RESULTS
  Significant overall decreases in body weight were apparent at the conclusion of both races. The mean relative body weight change after the 12-hour race was -2.89 +/- 1.56%, ranging from 0 to 6.5%. The mean relative body weight change after the 24-hour race was -5.05 +/- 2.28%, ranging from -0.77% to -11.40%. Of runners in the 24-hour race, 26% lost greater than 7% of baseline body weight during the race. During both the 12- and 24-hour races, the greatest weight change (decrease) occurred during the first 4 hours. Weight remained relatively stable after 8 hours, although a further decrease was apparent between 16 and 20 hours in the 24-hour participants. Weight change had no bearing on performance in the 12-hour race, whereas weight loss was positively associated with performance in the 24-hour race.
  
  
  CONCLUSIONS
  Our findings demonstrate that the majority of weight decrease/dehydration in both the 12- and 24-hour races occurred during the first 8 hours. Hence, to maintain body weight, fluid intake should be optimized in the first 8 hours for both 12- and 24-hour runners and in 16 to 20 hours for 24-hour marathon runners.
authors.affiliation: Section of Emergency Medicine, National Yang-Ming University, Taipei, Taiwan. wfkao@vghtpe.gov.tw
authors.forename: Wei-Fong
authors.initials: WF
authors.lastname: Kao
authors.forename: Chih-Ling
authors.initials: CL
authors.lastname: Shyu
authors.forename: Xiu-Wu
authors.initials: XW
authors.lastname: Yang
authors.forename: Teh-Fu
authors.initials: TF
authors.lastname: Hsu
authors.forename: Jin-Jong
authors.initials: JJ
authors.lastname: Chen
authors.forename: Wei-Chun
authors.initials: WC
authors.lastname: Kao
authors.lastname: Polun-Chang
authors.forename: Yi-Jen
authors.initials: YJ
authors.lastname: Huang
authors.forename: Fon-Chu
authors.initials: FC
authors.lastname: Kuo
authors.forename: Chun-I
authors.initials: CI
authors.lastname: Huang
authors.forename: Chen-Hsen
authors.initials: CH
authors.lastname: Lee
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012420:Running / Q000502:physiology*; D013997:Time Factors; D015431:Weight Loss