Water and sodium intake habits and status of ultra-endurance runners during a multi-stage ultra-marathon conducted in a hot ambient environment: an observational field based study - Costa, RJ S; Teixeira, A; Rama, L; Swancott, A J; Hardy, L D; Lee, B; Camoes-Costa, V; Gill, S; Waterman, J P; Freeth, E C; Barrett, E; Hankey, J; Marczak, S; Valero-Burgos, E; Scheer, V; Murray, A; Thake, C D (Nutr J, 2013)