title: Weight changes, medical complications, and performance during an Ironman triathlon.
abstract: BACKGROUND
  Subjects exercising without fluid ingestion in desert heat terminated exercise when the total loss in body weight exceeded 7%. It is not known if athletes competing in cooler conditions with free access to fluid terminate exercise at similar levels of weight loss.
  
  
  OBJECTIVE
  To determine any associations between percentage weight losses during a 224 km Ironman triathlon, serum sodium concentrations and rectal temperatures after the race, and prevalence of medical diagnoses.
  
  
  METHODS
  Athletes competing in the 2000 and 2001 South African Ironman triathlon were weighed on the day of registration and again immediately before and immediately after the race. Blood pressure and serum sodium concentrations were measured at registration and immediately after the race. Rectal temperatures were also measured after the race, at which time all athletes were medically examined. Athletes were assigned to one of three groups according to percentage weight loss during the race.
  
  
  RESULTS
  Body weight was significantly (p<0.0001) reduced after the race in all three groups. Serum sodium concentrations were significantly (p<0.001) higher in athletes with the greatest percentage weight loss. Rectal temperatures were the same in all groups, with only a weak inverse association between temperature and percentage weight loss. There were no significant differences in diagnostic indices of high weight loss or incidence of medical diagnoses between groups.
  
  
  CONCLUSIONS
  Large changes in body weight during a triathlon were not associated with a greater prevalence of medical complications or higher rectal temperatures but were associated with higher serum sodium concentrations.
authors.affiliation: UCT/MRC Research Unit for Exercise Science and Sports Medicine, P O Box 115, Newlands 7725, Cape Town, South Africa. sharwood@sports.uct.ac.za
authors.forename: K A
authors.initials: KA
authors.lastname: Sharwood
authors.forename: M
authors.initials: M
authors.lastname: Collins
authors.forename: J H
authors.initials: JH
authors.lastname: Goedecke
authors.forename: G
authors.initials: G
authors.lastname: Wilson
authors.forename: T D
authors.initials: TD
authors.lastname: Noakes
mesh_terms: D001794:Blood Pressure / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology; D003430:Cross-Sectional Studies; D003681:Dehydration / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D012007:Rectum / Q000502:physiology; D012307:Risk Factors; D012964:Sodium / Q000097:blood; D013177:Sports / Q000502:physiology*; D015431:Weight Loss / Q000502:physiology*
chemical_list: D012964:Sodium