Ad libitum fluid intake leads to no leg swelling in male Ironman triathletes - an observational field study

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(R) 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). 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