title: Ad libitum fluid intake leads to no leg swelling in male Ironman triathletes - an observational field study.
abstract: BACKGROUND
  An association between fluid intake and limb swelling has been described for 100-km ultra-marathoners. We investigated a potential development of peripheral oedemata in Ironman triathletes competing over 3.8 km swimming, 180 km cycling and 42.2 km running.
  
  
  METHODS
  In 15 male Ironman triathletes, fluid intake, changes in body mass, fat mass, skeletal muscle mass, limb volumes and skinfold thickness were measured. Changes in renal function, parameters of skeletal muscle damage, hematologic parameters and osmolality in both serum and urine were determined. Skinfold thicknesses at hands and feet were measured using LIPOMETER® and changes of limb volumes were measured using plethysmography.
  
  
  RESULTS
  The athletes consumed a total of 8.6 ± 4.4 L of fluids, equal to 0.79 ± 0.43 L/h. Body mass, skeletal muscle mass and the volume of the lower leg decreased (p <0.05), fat mass, skinfold thicknesses and the volume of the arm remained unchanged (p >0.05). The decrease in skeletal muscle mass was associated with the decrease in body mass (p <0.05). The decrease in the lower leg volume was unrelated to fluid intake (p >0.05). Haemoglobin, haematocrit and serum sodium remained unchanged (p >0.05). Osmolality in serum and urine increased (p <0.05). The change in body mass was related to post-race serum sodium concentration ([Na+]) (r = -0.52, p <0.05) and post-race serum osmolality (r = -0.60, p <0.05).
  
  
  CONCLUSIONS
  In these Ironman triathletes, ad libitum fluid intake maintained plasma [Na+] and plasma osmolality and led to no peripheral oedemata. The volume of the lower leg decreased and the decrease was unrelated to fluid intake. Future studies may investigate ultra-triathletes competing in a Triple Iron triathlon over 11.4 km swimming, 540 km cycling and 126.6 km running to find an association between fluid intake and the development of peripheral oedemata.
authors.affiliation: Institute of Primary Care and Health Services Research, University of Zurich, Zurich, Switzerland. beat.knechtle@hispeed.ch.
authors.forename: Michael
authors.initials: M
authors.lastname: Meyer
authors.forename: Beat
authors.initials: B
authors.lastname: Knechtle
authors.forename: Jolanda
authors.initials: J
authors.lastname: Bürge
authors.forename: Patrizia
authors.initials: P
authors.lastname: Knechtle
authors.forename: Claudia
authors.initials: C
authors.lastname: Mrazek
authors.forename: Andrea
authors.initials: A
authors.lastname: Wirth
authors.forename: Birte
authors.initials: B
authors.lastname: Ellenrieder
authors.forename: Christoph Alexander
authors.initials: CA
authors.lastname: Rüst
authors.forename: Thomas
authors.initials: T
authors.lastname: Rosemann